Why are listeners sometimes (but not always) egocentric? Making inferences about using others' perspective in referential communication.

Theory of Mind (ToM) is the ability to understand others' mental states, and that these mental states can differ from our own. Although healthy adults have little trouble passing conceptual tests of ToM (e.g., the false belief task [1]), they do not always succeed in using ToM [2,3]. In order to be successful in referential communication, listeners need to correctly infer the way in which a speaker's perspective constrains reference and inhibit their own perspective accordingly. However, listeners may require prompts to take these effortful inferential steps. The current study investigated the possibility of embedding prompts in the instructions for listeners to make inference about using a speaker's perspective. Experiment 1 showed that provision of a clear introductory example of the full chain of inferences resulted in large improvement in performance. Residual egocentric errors suggested that the improvement was not simply due to superior comprehension of the instructions. Experiment 2 further dissociated the effect by placing selective emphasis on making inference about inhibiting listeners' own perspective versus using the speaker's perspective. Results showed that only the latter had a significant effect on successful performance. The current findings clearly demonstrated that listeners do not readily make inferences about using speakers' perspectives, but can do so when prompted.

Introduction

Theory of Mind (ToM) is the ability to understand others’ mental states, and that these mental states can differ from our own. This ability is fundamental for navigating the social world in which we live. Without ToM, it would be impossible to achieve mutual understanding or even interpret others’ simple actions, e.g., a friend’s point to a peppermill on the dinner table. Although typically-developed adults have little trouble passing conceptual test of ToM, there is much variability in their propensity to use what they know about others’ mental states in ongoing communication (e.g., [2,3]). Instances of faux pas are regularly seen in daily life, and are often due to the actor or speaker not fully accounting for others’ mental states. For example, the result of the Great British Bake Off final in 2017 was revealed hours ahead of broadcast due to new judge Prue Leith forgetting that she was in a time zone hours ahead of the UK and congratulated the winner on Twitter prematurely. Real life egocentric errors that carry higher stakes can also be seen in the business and political domains (e.g., In the US presidential election campaign in 2016, Hillary Clinton calling half of Trump’s supporters “a basket of deplorables”, wiping out her chances of winning over their votes). Instances like these highlight that we cannot assume successful or consistent ToM-use among people who would clearly pass standard conceptual tests of ToM. Egocentric errors are frequently observed in real life, not only in face to face communication, but also over email communications [4]. On the other hand, such errors are far from ubiquitous: communicators frequently display sensitivity to perspective differences (e.g., [5-7]). This leads to a puzzle about why people only sometimes use their ToM abilities. In the present study we investigated the possibility that listeners have a tendency to overlook some of the inferential steps required to fully account for a speaker’s perspective. We employed a task that normally produces consistently high rates of egocentric errors (e.g., [2,3]), therefore allowing space for improvement in ToM-use.

Referential communication tasks provide an ideal context to systematically capture communicators’ successes and failures in using ToM (e.g., [2,3,5,6,8-12]). In order for communicators to correctly understand others’ reference, they need to account for the common ground they shared with their communicative partner while avoid referring to information privileged to themselves [13,14]. The premise of these tasks critically tests the degree to which communicators are able to use what they know about others’ mental states during language comprehension (e.g., [2,3,5,6] and language production (e.g., [11,15]). A widely-used task in this domain is the director task, which requires participants to take the role of listeners and follow instructions delivered by a director. Critically, there is a discrepancy between the participants’ perspective and the director’s perspective, as they each have a unique view of the same grid (see Fig 1). Some of the slots on the grid are open to both the director’s side and the participants’ side, therefore any objects placed in these slots are in their common ground. In contrast, some of the slots on the grid are blocked from the director’s view, therefore any objects placed in these slots are in the participants’ privileged ground, as these objects cannot be seen by the director. In order to correctly interpret the director’s utterances, participants need to realise that the director’s perspective content is different to their own. In particular, participants need to realise that the director has a restricted view of the grid, and that she can only see the objects in the common ground. This requirement is heavily emphasised in the introductory procedures to the task (see below for more detail). Critically, calculating the director’s perspective is not sufficient to succeed on the task: participants must also interpret the director’s utterances according to her perspective, not the participants’ own perspective. To do so participants must set aside or inhibit their own perspective, and realise that the director’s perspective means she cannot be referring to some objects. Failure to ignore their own perspective and successfully apply the director’s perspective leads participants to commit egocentric errors in referent selection and/or show egocentric tendencies in response time and eye movements. Given the importance of ToM-use in social cognition, variations of the director task have been widely employed to study the developmental changes [12,16-18], cross-cultural differences and similarities [19-21], individual differences in social and cognitive functioning [22,23], and neural-underpinnings of ToM-use [16,24,25].

Fig 1

Examples of the grid display.

An example of the experimental condition is shown on the left, with the control condition on the right. A critical instruction to accompany this display would be “nudge the large present one slot up”. The only difference between the experimental condition and the control condition is that the experimental condition contains a “distractor” (in this case, the largest present from participants’ view), which competes with a “target” (in this case, the largest present from director’s view) to be the best-fitting referent for the director’s critical instructions. In the control condition, the distractor is replaced by an “irrelevant object” (in this case, the barometer from participants’ view), which does not compete with target to be the best fitting referent.

A striking feature of the director task is the high rates of egocentric errors frequently observed [2,3,12,16,18]. What is more, attempts to reduce rates of egocentric errors have often been strikingly unsuccessful. Keysar et al. [3] attempted to maximise the saliency of a director’s perspective by implementing a number of measures. For instance, they had the participating listeners hide a referential competitor in an opaque bag themselves to highlight the director’s ignorance; they had the participants swap roles with the director during practice to highlight her perspective; they even assigned the director a false belief so that the director held a distinctively different belief to the participants. However, none of these measures made the listeners more successful at using the director’s perspective. Similar degrees of egocentrism were observed when the director had a salient false belief about the content of listeners’ privileged ground versus when she was simply ignorant about it. This suggests that saliency of the director’s perspective content is unlikely to account for the high rates of egocentric errors observed. Legg et al. [9] further confirmed that the level of difficulty in inferring a director’s perspective content did not have a significant effect on the degrees of egocentrism listeners displayed. In this study, listeners were no more successful in avoiding egocentric errors when the inferential process merely concerned computing her visual access (level-1 visual perspective) versus the way in which objects appeared to her (level-2 visual perspective). These findings suggest that the inference required to calculate others’ perspective content does not have a clear role in accounting for failure in ToM-use.

A mindreading model put forward by Apperly [26] suggests that mindreading involves three constituent stages: calculating others’ mental states, storing the calculated mental state, and using the calculated mental state to explain, predict, or interpret behaviour. Keysar et al [3] and Legg et al [9] demonstrated that unsuccessful mindreading is unlikely to arise from the calculation stage. Zhao et al. [18] studied the storage stage and showed that 8- and 10-year-old children committed more egocentric errors when they were required to remember whether an object belonged to the director’s perspective or their own privileged perspective. This suggests that egocentrism could be at least partly attributed to failure in the storage stage. However, in the director tasks where high rates of egocentric errors were observed in adults [2,3], there was no explicit requirement to hold the director’s perspective in mind, because unlike the Zhao et al. [18] study, the director’s perspective could always be inferred from the visual information available at the time of need. Therefore some of the egocentric errors previously observed are likely to arise from the final use stage. Specifically, having calculated the director’s perspective, participants need to do two things to use it successfully. Firstly, participants must ensure that they are guided by the director’s perspective rather than their own. Secondly, participants need to work out precisely how the director’s perspective constrains reference. It is worth noting that in standard versions of the director task, the director’s perspective and the participants’ perspective differ in their visual access to various objects, which corresponds to level-1 visual perspective judgements of what can be seen by others. The calculation of level-1 visual perspective content has been shown to be relatively effortless (e.g., [27,28]) therefore participants are unlikely to have difficulty in calculating the content of the director’s perspective. Instead, the critical process involved in this inferential step likely lies in inferring the implications of having different visual perspectives to the director. In the context of the director task, the implication is that the director’s instructions can be interpreted differently from participants’ own perspective versus the director’s perspective (e.g., the ‘large present’ in Fig 1 could be interpreted as corresponding to different objects from the director’s perspective versus the participants’ perspective). It is possible that the high rates of egocentric errors previously observed (e.g., [2,3]) resulted from failure to achieve either or both of these steps. Such perspective-taking failures are also seen in everyday language production. In the example we described at the start of this paper, Bake-off’s Prue Leith’s premature congratulation to the winner of the show is unlikely caused by a difficulty in understanding the concept of time zones, or an ability to understand that she has knowledge about the outcome of the show that is privileged to her but not the show’s viewers. However, when it mattered, she still failed to account for her viewers’ perspectives, spoiling the show’s finale. Instances of perspective-taking failures highlight the difficulty people encounter in using what we know about others’ mental states. Understanding these processes would cast new light on the nature of how people use mindreading information [26]. It is clear that having the conceptual understanding that people can have different perspectives does not guarantee successful use of such information. Therefore it is critical to examine the potential sub-processes involved in ToM-use.

We employed a variation of the computer-based director task that has been shown to produce high rates of egocentric errors [2]. In order to encourage participants to take the inferential steps required for successful ToM-use, we systematically manipulated the overt instructions to emphasise the need for participants to inhibit their own perspectives and to infer the way in which a director’s perspective constrains reference. In Experiment 1, prompts for the two steps associated with self-perspective inhibition and other-perspective-use were presented together. If the high rates of egocentric errors previously observed are driven by participants’ oversight of the inferential steps required, then the provision of an introductory example of the full chain of inferences should significantly reduce the rates of egocentric errors observed. Experiment 2 further investigated whether both prompts are required, and whether they need to be given sequentially.

Experiment 1

The current experiment compared ToM-use performance following two version of overt instructions: 1. a director’s perspective was made clear, and participants were instructed to take her perspective into account during the task. 2. exactly the same instruction as version 1, with the addition of an example of the full chain of inference required to successfully use the director’s perspective. The example instructs participants not to use their own perspective, and to use the director’s perspective to interpret her utterances.

Method

Participants

Sixty-eight participants (10 males, mean age 19.16 years, age range 18 to 23 years) gave informed consent to participate in the study and were tested by the same experimenter at the University of Birmingham. Ethical approval has been granted by the Ethics Committee at the University of Birmingham (reference: ERN_09–719). The individual whose image featured as the director in this manuscript has given written informed consent (as outlined in PLOS consent form) to publish their image. The sample size required to detect an interaction between condition and task instruction was calculated using G*Power. Fifty-two participants were required with power set to 0.8, effect size f set to 0.2. As this is a novel effect, we tested 68 participants to ensure that we are able to detect the effect. Participants were given course credit or a small honorarium as reward (the form of reward was not recorded for this experiment, hence could not be included as a random effect in the analysis). Three participants were replaced as two of the participants self-reported strategies unrelated to ToM-use, and the third participant attributed conflict between self and other perspectives to computer fault.

Design & procedure

We manipulated the overt instruction so that the way in which a director’s perspective constrains reference was either made explicit to the participants via the overt instructions or not. A 2 x 4 x 2 mixed design was employed with condition (control, experimental) and magnitude of common ground (3, 5, 7, 9) as within-participant variables, and task instruction (with-example, without-example) as a between-participant variable. The only difference between the experimental condition and the control condition is that the experimental condition contains a “distractor”, which competes with a “target” to be the best-fitting referent for the director’s critical instructions (see Fig 1 for an example). In the control condition, the distractor is replaced by an “irrelevant object”, which does not compete with target to be the best fitting referent. It is crucial to include such a control condition, as the processing cost associated with the control condition provides a baseline measure of the processing demands associated with visual search, speech processing, instructions following without perspective-taking, and object selection. Since the experimental condition and the control condition only differed by one object: the distractor versus irrelevant object, we can infer that any additional processing cost observed in the experimental condition compared to the control condition would reflect demand of perspective-taking, as opposed to processing visual stimuli, speech, instructions following, or object selection. The magnitude of common ground, which referred to the number of open slots on a grid, was manipulated in another series of unpublished studies. The with-example and without-example task instructions were both delivered as a combination of spoken instructions, images, and experimenters’ actions. The only difference between the two sets of instructions was that the with-example condition included an example to illustrate the way in which the director’s perspective should be used to interpret her utterances. The exact wording for the task instructions and their accompanying images can be found in Table 1.

Table 1

Instruction wording in Experiments 1 and 2.

All instructions in quotation marks were spoken, contents in parenthesis were acted out by an experimenter. The only difference between various conditions was the example given on Slide 3.

Slide	Spoken instruction	Accompanying image
1	E1 & E2: “In this experiment, you will see a director, like the one shown on the screen. You will also see a 4x4 shelf posited between you and her. There will be some objects on the shelf. The director will give you instructions to move some of the objects around.
	Some of the slots on the shelf are blocked from the director's point of view, and she does not know about the objects in those slots. Therefore she cannot ask you about those object. You would have to take this information into account when nudging the objects”
2	E1 & E2: “In the next 20–25 minutes, you will see a lot of pictures like this. This is the shelf I was talking about, there are 16 possible locations for objects to go. You will notice that some of the slots have green backgrounds. You are able to see the objects in these slots. However, the director is standing behind the shelf, on the other side. Therefore she doesn’t see and doesn’t know about any objects placed in those slots (point to the five blocked slots). Since she doesn’t know about these objects, she cannot possibly ask you to move any of them.”
3	E1 with-example condition & E2 other-explicit-self-explicit condition: “For example, if she asks you to “nudge the short torch one slot left”, although you might be tempted to move this object (point to the shortest torch), this object isn’t actually available to her. Therefore she cannot be talking about this object, she must be talking about this object (point to middle torch) instead, because this is an object that she can see and can talk about. Does this make sense?”
	E2 other-explicit- self-not-explicit condition: “For example, if she asks you to “nudge the short torch one slot left”, she must be talking about this object (point to middle torch). Because this is an object that she can see and can talk about. Does this make sense?”
	E2 other-not-explicit-self-explicit condition: “For example, if she asks you to “nudge the short torch one slot left”, although you might be tempted to move this object (point to the shortest torch), this object isn’t actually available to her. Therefore she cannot be talking about this object. Does this make sense?”
	E1 without-example condition & E2 other-not-explicit- self-not-explicit condition: “For example, if she asks you to “nudge the short torch one slot left”, you would have to consider her perspective when you follow her instructions. Does this make sense?
4	E1 & E2: “To make sure everything is clear to you, this is how the shelf looks from where the director is standing. Please keep her perspective in mind when you follow her instructions.”

The task instruction was followed by 2 practice images and 32 test images, presented in 4 test blocks. When an image appeared, participants had 5000ms to examine the image before hearing 3 to 5 instructions from the director, one of which was a critical instruction. A total of 128 instructions were presented, with 32 critical instructions. The critical instructions were “nudge the [scalar adjective] [noun] one slot [directional word]” (for the complete list of critical instructions, see Appendix A). Relational expressions were employed to maximise the likelihood of observing egocentric errors and the potential increase in successful ToM-use. The remaining 96 instructions were fillers, 32 of which contained scalar adjectives (14 of the scalar adjectives were redundant adjectives, included to minimise the likelihood for scalar adjectives to signal the need to take the director’s perspective), and 16 contained non-scalar adjectives (e.g., blue, included to minimise the likelihood for adjectives to signal the need to take the director’s perspective), and the remaining 48 filler instructions were simple noun phrases. All sentences were spliced together from individually recorded words to eliminate the possibility for participants to use co-articulation to identify a referent prior to the onset of the adjective or noun. If participants did not respond within 4000ms from the onset of the adjective (or noun where the instruction did not contain adjectives), then the trial timed out, and the next instruction was played or the next grid-image shown. As in Apperly et al. [2], participants responded with a computer mouse, by performing a “drag and drop” motion as if moving the selected object from one slot to another. Object selection accuracy and response time were based on the first mouse click participants performed following an instruction. Participants were informed that we were interested in their first mouse click, therefore they should consider carefully before making a mouse click. Interest areas were drawn around each slot on the grid, therefore a mouse click within the slot in which a correct object was positioned would qualify as a correct response. Response times were calculated from the onset of an adjective or noun until the first mouse click response.

Half of the images corresponded to the experimental condition, the other half corresponded to the control condition. In the experimental condition, the item that best fitted the director’s description on a critical instruction differed from the director’s point of view versus the participants’ point of view. For example, when the director asked for the “large present”, the item she referred to was the purple present in the left panel of Fig 1 as it is the larger of the two presents available to her (“target” hereafter). However, the item that best fitted the director’s description from the participants’ point of view was the white present (“distractor” hereafter). In order to correctly select a target, it was essential that participants utilized perspectival information to resolve reference. The control condition was identical to the experimental condition apart from that the distractor was replaced by an irrelevant item which did not compete as a potential referent from the participants’ perspective (e.g., a barometer, see right panel of Fig 1). Participants saw the grid images associated with both the experimental condition and its counterpart in the control condition. The grid images were positioned at least a full block of 8 trials apart, and in different halves of the experiment, minimising the possibility for the critical difference between the conditions to be recognised by participants. No participant was able to describe the critical difference between the two conditions during debrief.

Results

Trial level data and the R code used in the analyses from the current study can be found in the Supplementary Materials. We calculated the percentage of egocentric errors for each participant in each condition. An egocentric error refers to a response error of selecting the distractor rather than the target in the experimental condition. Selection of the irrelevant object in the control condition provides a baseline for erroneous selections in the absence of direct competition between the participants’ and the director’s perspectives on a closely matched grid image. Across the two experiments, only 2 of such selection errors were observed in the control condition. Selections of objects or spaces that are not distractors or targets were excluded from all analyses, as these errors are rare, and it is difficult to interpret the cause of such errors. Trials with response timeout were excluded prior to analysis, leading to exclusion of 4.41% of the critical trials from the current experiment. The considerably lower error rate in the control condition compared to the experimental condition lead to unequal variance between the two conditions, which made it questionable to include condition as a factor in an omnibus analysis. Therefore our analyses focus on percentage egocentric errors on the experimental conditions (for descriptive statistics, see Table 2). The overall rate of egocentric errors could reflect incorrect responses prior to participants’ first correct response, or participants’ consistency in using the director’s perspective, or to some combination of these factors. These factors are separately informative about how instructions affect performance, therefore we examined the effect of instructions on overall egocentric error rate, number of trials to first correct response, and error rate following first correct response.

Table 2

Descriptive statistics for Experiments 1 and 2.

E1		with-example		without-example
	Egocentric error (%)	5.48		55.84
	SD	14.18		34.42
	Number of trials to first correct response	1.44		4.58
	SD	0.73		3.34
	Error rate following first correct response (%)	9.03		50.58
	SD	15.28		33.74
E2		other-explicit		other-not-explicit
		self-explicit	self-not-explicit	self-explicit	self-not-explicit
	Egocentric error (%)	9.05	13.03	21.04	37.67
	SD	17.35	26.02	31.06	40.64
	Number of trials to first correct response	1.48	2.32	3.16	4.12
	SD	1.00	2.54	3.00	3.60
	Error rate following first correct response (%)	15.28	14.96	28.97	35.71
	SD	17.24	24.56	31.59	35.66

The combined results from the number of trials to first correct response and the error rates following first correct response can also help address an alternative account for any positive effect that the with-example condition might have on performance. Recall from the introduction that previous studies of perspective-taking during referential communication show a puzzling mixture of very good versus relatively poor performance. A potentially simple explanation of this pattern would be that studies demonstrating good performance simply employed clearer task instructions enabling more participants to understand that they should use their ToM abilities. This explanation would tell us something about the importance of instructions, but nothing about the underlying processes of ToM-use. If such an account were correct, then the with-example condition should not only require fewer trials until participants reach their first correct responses, but also show floor-level error rates following the first correct response, because superior instructions had removed the principal source of errors. To verify this alternative account, we will additionally compare the error rates following first correct response against zero. Response times from trials with correct responses were reported in the Supplementary Materials. Response time data should be interpreted with caution as these reports contain relatively small number of trials, due to exclusion of a large number of erroneous trials.

A generalized linear mixed effects model was fitted to egocentric errors using the glmer() function from the lme4 package in R [29]. The fixed effects were magnitude of common ground (3 slots, 5 slots, 7 slots, 9 slots), and task instruction (with, without explicit instruction to inhibit self-perspective and use the director’s perspective). Both fixed effects were included as both main effects and interactions in all models. Both fixed effects were coded with contrast coding, specifically deviation coding, where each level is compared to a grand mean. Participant and grid image were included as random effects. Our models for Experiment 2 additionally included experimenter and reward as random effects. This was not possible here, as all participants were tested by one experimenter, therefore experimenter was not entered as a random effect. Information on the form of reward participants received was not recorded at the time, therefore reward was not entered as a random effect. We attempted to fit models with maximal random effect structure to all models [30]. The maximal model included intercepts from both random effects, and random slopes for magnitude of common ground by participant, task instruction by grid image. The fitted model did not contain random slots for the magnitude of common ground by participant. The fitted model was used to determine the statistical significance of a given main effect or interaction by removing one main effect or interaction term from the fitted model at a time, and comparing the models with versus without a given effect. This comparison was conducted through the anova() function, which is suitable for comparing the variance for one or more fitted model objects.

The number of trials to first correct response and error rate following first correct response were aggregated by grid image and participant, therefore it was not possible to include these terms in mixed models. As there was no viable random effect to be included in the models, independent t-tests were carried out for these two dependent variables (for a summary of all analyses for the current experiment, see Table 3).

Table 3

Summary of mixed models from Experiment 1.

	β	SE	χ2	df	p
Egocentric error
instruction	-5.12	0.83	34.54	1	< .001
mag	-0.53	0.43	1.48	1	0.224
instruction*mag	-0.73	1.08	0.45	1	0.505
			t	df	p
Number of trials to first correct response
instruction			5.12	32.5	< .001
			t	df	p
Error rate following first correct response
instruction			-6.41	42.1	< .001

An effect of instruction was found in percentage egocentric error, number of trials to first correct response, and error rate following first correct response (see Fig 2). Participants’ performance was significantly better across these measures when the way in which the director’s perspective constrains reference was made explicit through a simple example in the instruction. The linear mixed effects models analysis on response times revealed a significant effect of condition (experiment > control), χ2 = 9.85, df = 1, p = .002, along with a significant interaction effect between condition and magnitude, p = .017. The full analysis can be found in the Supplementary Materials. To verify the possibility that the with-example condition merely clarified the instructions rather than improved ToM-use, the error rates following first correct response were tested against a floor-level. Error rates following first correct response in both conditions were significantly higher than floor-level (ts > 3.54, ps < .002, mean error rates were 9.03% and 50.58% for the with-example and without-example conditions, respectively), which does not lend support to such account.

Fig 2

Pirate plot for the percentage egocentric errors from Experiment 1.

Each circle represents the mean percentage egocentric error for a participant. The bold horizontal lines correspond to the condition means, the light-coloured bands around the means correspond to the confidence intervals.

Discussion

The current result showed that the provision of an exhaustive example of the way in which a director’s perspective constrains reference led to dramatically lower rates of egocentric errors. This suggests that the revised instructions likely helped participants to use the director’s perspective effectively. We do not think that the with-example condition merely presents an improved instruction, as participants in this condition were not only quicker to produce a first correct response, they were also consistent at maintaining a lower (but above floor) level of egocentric errors since the first correct response. Furthermore, performance following “standard” instructions (without the example of the full chain of inference) was previously found to correspond to social functioning profiles as measured by autistic and psychotic characteristics [22]. Individuals who score highly on either an autistic or psychotic characteristic were less likely to succeed in considering a director’s perspective compared to individuals who score evenly on the two characteristics. This suggests that social functioning may account for communicators’ propensities to infer the relevance of their communicative partners’ perspectives in the absence of any additional incentives.

It is worth noting that the with-example condition served two functions. Firstly, it highlighted the way in which participants’ own perspective led to an incorrect response “… you might be tempted to move this object, but this object isn’t actually available to her…”. Therefore participants may have been prompted to inhibit the use of their own perspective to interpret the director’s utterance. Secondly, it highlighted the way in which the director’s perspective should be used to interpret her utterances “… she must be talking about this object instead, because this is an object that she can see and can talk about…”. To this end, participants may have been prompted to infer the ways in which the director’s perspective should be used to interpret her utterance. It is noteworthy that successful implementation of either step would lead to better performance. This is because a full inhibition of self-perspective would lead participants to only consider objects in the common ground as potential referents, resulting in no egocentric errors. On the other hand, a correct inference about the ways in which the director’s perspective should be used would also lead to correct interpretation of her utterance. Therefore the current experimental finding could be explained by either successful self-perspective inhibition or other-perspective-use, or both. In other words, the current experiment’s exhaustive example may not be necessary. It is possible that just one of the components of the example is critical for improving the use of the Director’s perspective. Experiment 2 was designed to disentangle the effects of self-perspective inhibition and other-perspective-use. It also served as a replication of the striking reduction in egocentric errors observed in Experiment 1 without the variation in the magnitude of common ground.

Experiment 2

In the current experiment, four versions of overt instructions were employed, each placing selective emphasis on self-perspective inhibition versus other-perspective-use. The four versions of instructions were constructed in a factorial manner so that the effects of self-perspective inhibition and other-perspective-use can be fully dissociated. It is possible the two effects to be individually effective in boosting ToM-use. It is also possible that a combined effect is necessary to increase the propensity of ToM-use, in which case an interaction effect will be observed.

One hundred participants (19 males, mean age 20.41 years, age range 18 to 29 years) gave informed consent to participate in the study and were tested by three experimenters at the Lancaster University. We expect the effect sizes for the current experiment to be smaller than Experiment 1, as we are attempting to separate the contributions of the two instruction steps. G*Power indicated that 76 participants were needed to detect an interaction effect, with power set to 0.8 and assuming an effect size of 0.2. Therefore 100 participants were recruited to ensure sufficient power is achieved. Six participants were replaced as they self-reported strategies unrelated to ToM-use.

A 2 x 2 x 2 mixed design was employed with condition (control, experimental) as a within-participant variable, other-perspective-use (other-explicit, other-not-explicit) and self-perspective-inhibition (self-explicit, self-not-explicit) as between-participant variables (see Table 1 for wording of instructions). Each participant was assigned to one of four versions of overt instruction. The remaining aspects of the design was identical to Experiment 1, with the exception of the number of objects on the grid in the current experiment was fixed at 8, so that it matched the complexity of the grid employed in a widely employed version of the director task [2].

Trials with response timeout were excluded prior to analysis, leading to exclusion of 7.13% of the critical trials from the current experiment. The analysis strategy was identical to that of Experiment 1, with the following exceptions. The fixed effects were other-perspective-use (other-explicit, other-not-explicit) and self-perspective-inhibition (self-explicit, self-not-explicit). Participant, grid image, reward (cash, course credit), and experimenter (RA 1, RA 2, RA 3) were included as random effects. Models with only participant and grid image as random effects were highly similar to the models that had included reward and experimenter as random effects. The fitted model contained intercepts for all random effects, and random slopes for self-perspective-inhibition by grid image, the interaction between self-perspective-inhibition and other-perspective-use by grid image.

The two forms of reward were not designed to provide differentiating incentives for performance. Both forms rewards were advertised as compensation for participants’ time rather than direct incentive for performance. Nonetheless, to check whether this random effect significantly alters the model fit, we compared a model with versus without the random effect of reward. Comparison showed no significant difference between the two models, χ2 = 0.03, df = 1, p = .864, BF01 = 37.04. Bayesian factor (BF01) was calculated to quantify evidence for a null model relative to an alternative model. The null model includes all fixed and random effects apart from the random effect of reward. The alternative model which additionally includes a random effect of reward was compared against the null model. The Bayes factor was calculated from the Bayes information criteria (BIC) obtained from the null and alternative models [31]. The BF01 indicates that the alternative model was 37.04 times less favourable than the null model. This suggests that reward is very unlikely to alter the model fit.

The number of trials to first correct response and error rate following first correct response were aggregated by grid image and participant, therefore it was not possible to include either terms in the mixed models. These models had reward and experimenter as random effects. Maximal models were fitted to both the number of trials to first correct response and error rate following first correct response. Both models contained intercepts for reward and experimenter, slopes for self-perspective-inhibition by reward, other-perspective-use by reward, the interaction between self-perspective-inhibition and other-perspective-use by reward, self-perspective-inhibition by experimenter, other-perspective-use by experimenter, and the interaction between self-perspective-inhibition and other-perspective-use by experimenter (for a summary of all analyses for the current experiment, see Table 4).

Table 4

Summary of mixed models from E2.

	β	SE	χ2	df	p
Egocentric error
self	0.61	0.77	0.63	1	0.428
other	2.12	0.76	7.69	1	0.006
self*other	1.80	1.55	1.78	1	0.182
	β	SE	χ2	df	p
Number of trials to first correct response
self	0.99	0.53	2.96	1	0.085
other	1.66	0.52	4.12	1	0.042
self*other	0.56	1.55	0.13	1	0.721
	β	SE	χ2	df	p
Error rate following first correct response
self	-0.04	0.05	0.45	1	0.500
other	-0.13	0.08	1.48	1	0.225
self*other	-0.13	0.17	0.56	1	0.453

Effects of other-perspective-use on percentage egocentric errors and number of trials to first correct response were observed (other-explicit < other-not-explicit, see Fig 3). The instruction to inhibit participants’ own perspective did not have a significant effect on egocentric error (BF01 = 27.78). The interaction between self-perspective-inhibition and other-perspective-use was not significant (BF01 = 15.63). The linear mixed effects models analysis on response times only showed a significant effect of condition, χ2 = 4.04, df = 1, p = .044 (control < experimental).

Fig 3

Pirate plot for the percentage egocentric errors from Experiment 2.

Each circle represents the mean percentage egocentric error for a participant. The bold horizontal lines correspond to the condition means, the light-coloured bands around the means correspond to the confidence intervals.

Replication of Experiment 1

Direct comparisons between the other-explicit-self-explicit condition (equivalent to the with-example condition in Experiment 1) and other-not-explicit-self-not-explicit condition (equivalent to the without-example condition in Experiment 1) showed clear replication across all dependent variables: percentage egocentric error (p <. 001, other-explicit-self-explicit < other-not-explicit-self-not-explicit), number of trials to first correct response (p = .001, other-explicit-self-explicit < other-not-explicit-self-not-explicit), and error rate following first correct response (p = .014, other-explicit-self-explicit < other-not-explicit-self-not-explicit). Additionally, the error rates following first correct response across all conditions were significantly higher than floor level (ts > 3.05, ps < .006; mean error rates ranging from 14.96% to 35.71%), once again providing no evidence for the alternative account that improved performance was merely driven by clearer instructions.

The current experiment played a critical role in disentangling the respective effects of self-perspective inhibition and other-perspective-use. Results showed that selective emphasis on the way the director’s perspective constrained reference clearly helped participants to infer the correct ways in which to use the director’s perspective. This suggests that the ways in which the director’s perspective constrains reference is the processing step participants most likely neglected, and hence benefitted from being prompted via explicit instructions.

Interestingly, the instruction to inhibit the use of one’s own perspective had no significant effect on measures of egocentrism. One possible explanation is that one’s own perspective is salient and frequently used, therefore it cannot be easily modulated via instructions. However, it is unlikely that participants lack the requisite cognitive ability to inhibit their own perspective. As shown by Apperly et al. [2], participants performed with much greater accuracy on a director task when instructed to adopt a rule-based strategy to “discount all slots with grey background” compared when instructed to “take the director’s perspective into account”. Curiously, the current results suggest that even when specifically instructed to inhibit their own perspective, participants do not appear to spontaneously adopt such a simple discounting strategy. In contrast, a dramatic improvement in perspective-taking performance was seen when an exhaustive instruction to both inhibit self-perspective and to use the director’s perspective was given. This highlights the possibility that self-perspective inhibition may need to be understood in the full context of perspective-taking. It is not sufficient for participants to be instructed to not use their own perspective if they do not know whose perspective they ought to adopt and how to do so, which may boil down to being sufficiently incentivised to invest the cognitive effort. Relatedly, the current results suggest that instructions for participants not to use their own perspective to interpret the director’s utterance did not sufficiently incentivise them to take the next inferential step and work out a way to use the director’s perspective. This further confirmed that inference about the ways in which the director’s perspective constrains reference is the processing step most likely neglected, as it was still overlooked when a different part of the inference steps was modelled in the instructions.

General discussion

The current findings demonstrated that listeners tend to overlook the inferential steps required to successfully use speakers’ perspectives, but can do so when prompted via instructions. Experiment 1 showed that the provision of a clear introductory example of the full chain of inferences required to successfully use a speaker’s perspective led to large improvement in listeners’ performance. Experiment 2 provided a replication of the key contrasts in Experiment 1, and further specified that the inferences about using a speaker’s perspective, but not inhibiting the listeners’ own perspective, played a significant role in lowering rates of egocentric errors. These results suggest that listeners do not need to be provided with an example of the full chain of inference in order to perform at a high level. Instead, listeners benefitted specifically from a prompt to identify precisely how a speaker’s perspective constrains reference.

Modelling inferential steps required for successful ToM-use

The current findings replicated previous observations that when listeners were simply instructed to take a speaker’s perspective into account without specific instructions to inhibit their own perspective or use the speaker’s perspective, they commit high rates of egocentric errors. This indicates that in the context of this experimental task, the propensity for listeners to invest the cognitive effort to take these inferential steps is low. In contrast, when small but systematic manipulations of the overt instructions were employed to model the inferential steps required to use the speaker’s perspective, performance improved considerably. This suggests that the provision of an example of the inferences required to use the speaker’s perspective was sufficient to prompt successful ToM-use.

Such effects were not only observed in rates of egocentric errors, they were also seen in the number of trials to first correct response across both experiments. This indicates that the revised instructions not only reduced rates of egocentric errors overall, it also made participants faster to implement the correct strategy of taking account of the director’s perspective. Taken alone, this finding might suggest that participants simply found it easier to understand that they should take account of the director’s perspective when given the revised instructions. Importantly, we think this may not be the full story, because the revised instructions also reduced participants’ error rate after their first correct response (in Experiment 1), and these egocentric errors after a first correct response were not eliminated (in either experiment). This is not the pattern that would be expected if using the director’s perspective was perfectly easy for participants once the revised instructions had enabled them to perform the task in the way intended. Instead we suggest that the revised instructions may have incentivised participants, via concrete examples, to make the required inference about using the speaker’s perspective until they have successfully resolved a critical reference.

Interestingly, effects of instruction on other-perspective-use were seen in the overall rates of egocentric error and the number of trials to first correct response, but not in error rate following first correct response. Notably, this measure did capture differences between the “all or nothing” conditions (the with-example versus without-example conditions in Experiment 1 and the other-explicit-self-explicit versus the other-not-explicit-self-not-explicit conditions in Experiment 2). This suggests that highlighting the ways in which the speaker’s perspective constrains interpretation of their instructions may not on its own offer sufficient incentives for participants to use the speaker’s perspective consistently, making it possible to observe an additional benefit from being prompted to ignore one’s own perspective.

The current study identified two possible sub-processes in the use stage of the Apperly [26] mindreading model. In order for listeners to successfully use what they know about a speaker’s perspectives, they need to inhibit information privileged to themselves, and infer how the speaker’s perspective constrains interpretation of their message. The current finding that prompts for listeners to use a speaker’s perspective significantly reduce rates of egocentric errors indicates that listeners were unlikely to make such inferences spontaneously. In contrast, prompts for listeners to inhibit their own perspective did not significantly lower rates of egocentric errors overall. We assume that self-perspective-inhibition is nonetheless integral to ToM-use, but that these results indicates that prompting participants to inhibit their own perspective had little overall effect, as discussed in Experiment 2. The dissociated effects of self-perspective inhibition and other-perspective use could help explain the high rates of egocentric errors observed in previous studies [2,3], and potential reasons for the great difficulty in lowering rates of egocentric errors. It seems likely that listeners know that they need to account for the speaker’s perspective in some way, and they know that this implies that they should not use their own perspectives to interpret the speaker’s utterance. However, not all listeners spontaneously inferred the ways in which the speaker’s perspective constrains interpretation of her instruction.

Variability in ToM-use

The current findings revealed that consistency in ToM-use cannot be taken for granted. This echoes recent work which suggests that the context and saliency of the cues associated with self and other could alter the ways in which perspectives are inferred and considered over the course of an interaction [32-34]. Additionally, a conversational partner and their social relationship with the listener could determine the degrees to which listeners are motivated to take their partner’s perspective into account [35]. Furthermore, specific conversational goals could also affect the degrees to which speakers display sensitivity towards their listener’s perspective [36]. Unlike conceptual tests of ToM, which typically delivers a pass versus fail verdict, ToM-use clearly varies according to a wide range of contextual factors. On the one hand, this may fit with our intuition about the variability of everyday social interactions. Faux pas do occur, yet they do not occur all of the time nor do they always occur to the same individual. On the other hand, the variability in ToM-use makes for a difficult theoretical debate. It is possible that the ongoing debate about whether listeners readily take a communicative partner’s perspective into account is unnecessarily dichotomous. It may be more productive to identify the context in which communicators succeed or fail to account for others’ perspective. Additionally, with large degrees of variability in the experimental paradigms employed and the task instructions delivered, it is critical for future work to systematically report full instructional materials, so we can begin to understand the ways in which communicators may be incentivised to take others’ perspectives.

Conclusion

The current findings clearly demonstrated that listeners do not readily make inferences about using speakers’ perspectives, but can do so when prompted. Successful referential communication requires listeners to infer that 1. they should not use their own perspective to resolve reference 2. the specific ways in which a speaker’s perspective constrains reference. Two experiments showed that an example of the full set of inferential steps required led participants to much greater levels of success in referential communication. Furthermore, specific prompt to use the speaker’s perspective on its own was effective in boosting performance. The current findings suggest that inference about the ways in which others’ perspectives need to be used is likely to be the primary obstacle to successful referential communication. Furthermore, simple manipulations such as an introductory example of the inferential steps required, can incentivise listeners to invest the cognitive effort to overcome such obstacles. Finally, the current findings provide an important foundation for advancing our knowledge about individual differences in mindreading in real life. A fruitful future direction would be to investigate the interactions between individual differences in the propensity to make the required inferences at the right time, cognitive flexibility (e.g., [10], and social functioning (e.g., [22,35]). Such insights will bring us closer to understanding the successes and failures in everyday mindreading.

RT analysis.

(DOCX)

Click here for additional data file.

Complete list of critical instructions.

(DOCX)

Click here for additional data file.

9 Mar 2020

PONE-D-20-01714

Why are listeners sometimes (but not always) egocentric? Making inferences about using others’ perspective in referential communication

PLOS ONE

Dear Dr Wang,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

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I carefully read the manuscript myself and asked two reviewers, both experts in perspective-taking and referential communication to evaluate the quality of the manuscript. The reviewers provided what I consider to be excellent and fair critiques, as well as several suggestions for improvement. Based on the reviewers’ comments, their ratings, and my own evaluation of the manuscript, I am pleased to offer you an opportunity to revise and resubmit an updated manuscript for potential publication in PLOS One. Note that this invitation to revise does not constitute a guarantee of eventual acceptance. If you choose to revise the manuscript, I will likely send it to the same reviewers to reevaluate. I also ask that you please provide point-by-point responses to each comment, either describing changes made in response to the comment or explaining why no change was made.

For the content of the reviews, I will not repeat all the various issues as they speak for themselves, but I will focus on a few issues that were particularly salient.

Both reviewers question the theoretical claims that are being made. Reviewer 1 would like to know more about the motivation and background that drove this work and Reviewer 2 wonders what is exactly meant by claims concerning the heart of the motivation, this idea of “full chain of inferences.” In my own reading, I too wanted a clearer accounting of what you exactly meant by the inferential steps that are being examined and a more explicit foreshadowing of how these steps are being manipulated within your paradigm/instructions. It seems that what you mean by “full inferential” (or “full chain of inferences”) is this idea of “other-explicit” and “self-explicit,” that is, a speaker has a unique perspective that needs to be taken into account and the self has a unique perspective that might been to be overridden. In the Introduction, the only inferential step that is emphasized is the “other-explicit.” It is only when the reader gets to the Methods that what is meant by full inferential steps (at least I think) is made clear - and really, it was only when reading through Table 1 and 2 captions that the ideas began to fall into place.

Reviewer 2 also wonders whether their understanding of the results of Experiment 2 - as being a sequential step of inference - is correct, and if so, greater discussion of what this means in terms of cognitive processing is needed.  I share with Reviewer 2 a concern about whether my understanding of the claims is correct and what this means for interpretation. For example, there is a claim repeated in the Discussion that having the full chain of inferences required to use the speaker’s perspective was sufficient to prompt successful ToM-use. But based on the results from Exp 2, I do not quite see how this can be true. Do not the results show that having just an other-explicit component produced a similar pattern of results as having both other-explicit and self-explicit components in the instructions? If so, then having examples with a full chain of inferences is not required (as stated on line 447 and in the Conclusion section). It is useful but not absolutely necessary.

I should note that when reading Reviewer 2’s point above, it also made me think of how this all relates to the theoretical framing used in the Introduction, namely the section on p. 7 lines 130-145 on Apperly’s three constituent stages. I would like to see how this earlier theoretical framing helps informs the current results. In the Introduction it is stated that previous studies observed egocentric errors at the “use” stage of Apperly’s model, but it seems that something else is being argued here for the current paper. The issue instead is about “calculating” not just others’ mental states (other-explicit) and explicitly recognizing one’s own perspective as being a potential distractor (self-explicit). But I am unclear on these finer theoretical points and how it relates to a full chain of inference.

There were also potential study design concerns that raised red flags for interpretation. For example, Reviewer 1 notes that in the error rate is very high in the instruction condition without examples. Reviewer 1 asks whether the error rate is based on participants' final selection. This question dovetails with Reviewer 2’s astute observation that it is unknown how correct object selection (and what constituted an error) was operationalized. Another red flag brought up by Reviewer 1 is why both object size and color were varied within targets and distractors. I agree that this makes the correct (ToM) selection harder to process and could be contributing to the high error rate. And lastly, Reviewer 2 asks for greater clarification on whether the control and experimental versions were in the same block as this definitely could confound results. Where limitations exist, please be sure to make corrections and/or address them thoroughly in the Discussion.

Reviewer 2 also makes the excellent point about this issue of the sensitivity of your measures to fully capture the cognitive dynamics that seem to be of interest in this paper. That is, you are interested in how response behavior changes over time. I strongly encourage you to consider adding trial ID as a fixed effect as I agree it would give you much better insight (perhaps error rates drop more dramatically over time in the full inferential sequence instructions than in the partial inferential sequences). But whether you add or not is not a condition for acceptance, but it would be good to have some speculation on this matter in the Discussion.

In conclusion, although there are several major issues that need to be addressed, I hope they can be resolved because the topic is very interesting and I think this work can make an important contribution to the field.

Again, please address every concern raised by the reviewers, as well as my specific comments that follow below. I look forward to seeing your revised version. Thank you. -Nick Duran

MY OWN ADDITIONAL COMMENTS:

Plos One puts great value on data availability and transparency in the code for statistical analysis. Perhaps I missed it, but is this information made available to the reader who might be interested in replication or even checking the statistical models for accuracy? Such data could be made available on an OSF repository (osf.io).

Exp 1.

For clarification, it would be good to integrate into the main prose the exact nature of the manipulations mentioned in the Table 1 and 2 captions.

I would be interested in seeing the specifications within G*Power for determining sample size for Exp 1 and Exp 2. Given statistical models that involve between-subjects factor and interaction effects, both studies seem underpowered. However, I am more than willing to concede that I am making incorrect assumptions about how you determined sample size.

What was the original rationale for the control condition in this study? It was eventually dropped from analysis because participants made so few errors, but curious why errors were even expected to begin with?

p. 12, line 235: Please provide further explanation for why a large number of trials with correct responses were lost to high rates of error. What is the nature of this error?

p. 13, line 245: what exactly is the contrast coding scheme used?

p. 14, line252: what statistical test did you use to do this comparison?

In Exp 1 Discussion, I could not follow the argument being made about social functioning profiles (around line 287). Is this to make an argument that mere instructions are sufficient for bringing greater awareness/relevance to a director’s perspective? Please clarify in the prose.

Exp 2.

For setting the effect size, you state that you expect a smaller effect size from Exp 1. Why then choose an effect size of 0.6 for Exp 2 when it was set at 0.2 for Exp 1?

What was the rationale for fixing the grid size to 8 in Exp 2 when it was allowed to vary across a range for Exp 1?

The alternative hypothesis on page 20, starting line 383, is hard to follow and it took me some time to work out. I think what is being claimed is that an ego-centric bias was still compete with responses even with the clearest of instructions. Is this right? And this appears to be evidenced with the more detailed instruction (other- and self-explicit) where the error rate following first correct response is still high (above 0) and does not vary from that much from the less detailed instructions? It would be useful to know which numbers are being compared from Table 2 to make these claims. Also, the introduction of the alternative hypothesis arrives out of the blue. I would recommend introducing the alternative hypothesis earlier as a target for analysis/interpretation (rather than doing it in the Results section), or treat it as a standalone issue/explanation as you do with the section “Replication of Experiment 1.”

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Please include the following items when submitting your revised manuscript:

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Reviewer #1: Partly

Reviewer #2: Yes

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5. Review Comments to the Author

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Reviewer #1: This research examines the role of explicit instructions on listeners’ perspective-taking in the referential communication task. When the director’s scene and the listener’s scene differ, the listener needs to consider the common ground rather than taking their privileged ground. Previous studies have shown that listeners are not always successful to take the director’s perspective to identify a target following the director’s instruction. In two experiments, the authors manipulated the types of instructions and tested listeners' perspective-taking. The results showed that listeners made fewer egocentric errors when they were given explicit instructions with examples (E1). Especially, explicit instructions on using the director’s perspective modulated listeners’ performance, but instructions on inhibiting their privileged perspective did not help (E2). Thus, the findings showed that listeners can take the director’s perspective when they are prompted with appropriate instructions.

I have a few comments and questions below.

First of all, I was not fully convinced with the motivation of this research. It is not quite surprising to see participants’ performance improved with explicit instructions. In introduction, it needs to build theoretical motivation and background that drove this research.

Especially, providing explicit instructions in this research may lack ecological validity. In everyday life, we are not told about perspective differences between partners. We naturally notice it and integrate that information in language processing. I think it is OK to use manipulations that lack ecological validity, but it needs justification. In that sense, it would be helpful to read about theoretical motivations about this research question/manipulations in introduction (and theoretical implications in discussion as well).

Secondly, in this sort of experimental paradigm in which perspective-taking is tested, researchers have manipulated only the “size” of critical items, the color remained the same (Ryskin et al., 2015). However, in this research, for example in Fig 1, the colors of the three presents are different and I think this is problematic. People use color adjectives all the time, and especially in Fig 1, speakers would not describe the target item using a size adjective. They would be highly likely to describe it using a color adjective (e.g., the purple present). If so, when participants heard the size adjective, it is just difficult for them to process. Why would you use a difficult size adjective when you can simply use a color adjective? I was wondering if all items were like in Fig 1 (critical items with different colors)? Or do critical items in Fig 1 and Table 1 happen to have different colors? It needs to be clarified.

Thirdly, the results are quite straightforward, but I was surprised by a high rate of errors that participants made especially in the condition without examples (E1 and the comparable condition in E2). Was it based on their final selection? Then, this means that more than half of the time, participants made egocentric errors in E1 (without-example). I understand that listeners consider egocentric knowledge in the middle of processing but it’s surprising that they made a final selection more than half of the time based on their egocentric knowledge. It would be great to clarify the dependent measure and I also wonder if there was a procedure to confirm that participants understood the experimental setting (e.g., what the green background indicated…).

Regarding the dependent measure, in the results, the authors analyzed the response time (pg. 14) as well as other measures (egocentric error, # of trials to first correct response, and error rate following first correct response), but descriptive stat of response time was not reported.

Minor points:

In E2, the authors included grid image, reward, and experimenter in the model. To make this consistent across experiments, it needs to be done in E1 as well. (Or if it is already done, it needs to be reported.)

In Table 1, the condition labels were not clear. I had to read back and forth to understand each condition. If it can be clarified, it would be helpful.

Reviewer #2: Summary: Across two experiments, the authors examine the effect of instructions on the distribution of egocentric responses in the "director task". The findings suggest that instructions about the inferential steps of assessing the director's perspective reduce the egocentric errors. Experiment 2 clarifies that it is the instructions' emphasis on the use of the task partner's perspective that drives this effect.

I have reviewed this article before at another journal. In this review, I focus my assessment on the extent to which the authors addressed my previous comments adequately in this submission. As I noted in my previous review, overall, I appreciate the novelty of the study in disentangling the effect of instructions to inhibit one's perspective vs. to use the task partner's perspective.

The authors effectively addressed one of my earlier comments about the theoretical framing (namely, about instructions previously being framed as motivating listeners to make inferences about the speaker’s perspective). Still, a number of my previous comments persist, including methodological and analytical points that could have been easily clarified.

I present these pending methodological issues next:

1. Please be explicit about whether participants saw both the control and experimental version of an otherwise identical display (i.e., whether they saw both displays shown in Figure 1). If so, I assume that critical and experimental versions were not in the same block, since this contrast could highlight the disparity between self and other perspectives and could confound the results. In either case, please specify how items were distributed across trials and blocks.

2. The distinction between conditions (control, experimental) is opaque upon first mention (p. 9), and is not fully described until p. 11. Please establish early on that these terms have to do with the absence vs. presence of a distractor in the trial.

3. It’s not clear initially, on p. 9., what the "magnitude of common ground" means (“3, 5, 7, 9”). On p. 13 the authors suggest that these values refer to "slots", but whether they are slots in common ground or NOT in common ground remains unclear. (Figure 1 suggests that it's the latter, seeing that there are 5 occluded and 11 open slots.) Please clarify.

4. It's not clear what would constitute egocentric errors in the control condition (p. 12, line 222). If the correct selection is the same object from both the participant's and the director's perspective, I don't follow how there could be an egocentric error to even yield the "2 egocentric errors” observed in the control condition across the two studies. Did the authors count the selection of the irrelevant object as an egocentric error (under the rationale that it is at the same location as the distractor/egocentric item of a corresponding display)? That doesn’t seem to be a felicitous interpretation of “egocentric”.

5. Please specify how correct object selection and response times were operationalized. Was response time based on the first click on the computer screen? on the release of the drag-and-drop gesture? on the final object selection or drag-and-drop release? All of these definitions are plausible. What counted as correct object selection: clicking anywhere in the cell of that object or at a more circumscribed area? Please clarify how data was collected from participants' interaction with the displays.

Some persisting theoretical points:

1. The authors refer to the instructions as describing the "full chain of inferences". What is that chain of inferences exactly? Is the chain of inferences: “Can she see my largest present? If yes, select. If not, which is the next largest present?” Or something else? In the Conclusion section, the authors present two inferences: “1. [Listeners] should not use their own perspective to resolve reference, 2. the specific ways in which a speaker’s perspective constrains reference.” Is this the chain of inference? If so, framing this as a chain suggests a sequential order. And if that’s the claim, the authors need to be explicit about how their results from Experiment 2 support it.

2. In this submission it’s not as clear what the rationale is of choosing the 3 DVs (overall rate of egocentric errors, number of trials to first correct response, and error rate following first correct response). The inclusion of the two latter metrics suggests that the first correct response reveals something important about the listener’s cognitive dynamics throughout the experiment. But the authors don’t explain how and why. Much later in the paper (p. 20, line 383-386) the authors suggest that they use these measures to test the alternative hypothesis that the instructions fully clarified what participants should do. The connections between the choice of these measures, the authors’ preferred hypothesis, and this alternative hypothesis need to be clarified.

As I recommended previously, instead of or in addition to these coarser-grained DVs, the authors could include trial id as a fixed effect in their models. Such an exploratory analysis could offer insights about the stabilization of other-centric responding over time under the different instruction conditions.

A related point: the authors suggest that, because the listeners’ error rates were substantially different from 0% after their first correct response, listeners “did not simply grasp what they were supposed to do” after the instructions. I’m not sure what “grasping what they were supposed to do” means here. But as I pointed out before, perspective-taking is not all-or-none; it need not be invariably at floor or at ceiling.

I leave it up to the Action Editor whether the authors should conduct additional analyses to examine at the distribution of egocentric errors over time in finer grain. But given the authors' theoretical points about sub-stages in perspective-taking and chains of inference in resolving reference, I suggest (as I did before) that they consider related work on how perspective-taking choices evolve and stabilize over time, not just within trials but across trials, over the course of an interaction (e.g., see Duran & Dale, 2014; Duran & Dale, 2011; Dale, Galati, et al., 2019; Galati, Dale, and Duran, 2019).

Small points

• p.4: Thanks for unpacking and future-proofing the Hillary Clinton example. Just a typo: “winner” -> “winning”

• p. 12, line 222: “excluded prior analysis” -> “excluded prior to analysis”

• Please replace R and lmer syntax with words in the text (namely, avoid | and * ).

• Footnote 3: incentivises -> incentives

• The two Experiments don't report results consistently. E2 includes Bayes factors, but E1 does not. Please make them consistent.

Alexia Galati

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6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

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Reviewer #1: Yes: Si On Yoon

Reviewer #2: No

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9 Jul 2020

Please see attached 'response to reviewer' document

Submitted filename: Response to reviewers.docx

Click here for additional data file.

7 Sep 2020

PONE-D-20-01714R1

Why are listeners sometimes (but not always) egocentric? Making inferences about using others’ perspective in referential communication

PLOS ONE

Dear Dr. Wang,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

==============================

Thank you for this resubmission and the obvious efforts in addressing the comments and concerns from the first round of reviews. I believe the manuscript to be much improved because of these efforts, a sentiment shared by the reviewers.

As you can see from the new reviews - which I thank the reviewers for doing with such care - there are still issues to be resolved. Many of these revolve around a theoretical framing that needs to be further clarified and strengthened. There is no requirement here to justify the importance of your theoretical stance, but merely to provide enough detail to remove ambiguity in how your conclusions relate to your data and a larger literature. Your manuscript is strong on all of PLOS ONE’s publishing criteria, except for one: "Conclusions are presented in an appropriate fashion and are supported by the data.” This is not a seriously damning weakness, but a few claims/conclusions need to be tempered given plausible alternative explanations and a referential communication task that has been questioned by others for its ability to genuinely capture perspective-taking behaviors in richer communicative scenarios. The suggestions for how to temper are provided by reviewers. I also urge you to seriously consider other suggestions for how to better draw out the novelty of your findings and their implications, as well as where greater precision in your interpretations could be made.

As before, please address every concern raised by the reviewers by directly communicating what change was made to your manuscript because of the comment, or justification for why you did not choose to make a change.  I look forward to seeing your revised version. This paper should make a strong contribution once all points are addressed. Also know that I am committed to expediting this manuscript to the next stage assuming the necessary changes have been made.

Sincerely, Nick Duran

==============================

Please submit your revised manuscript by Oct 22 2020 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

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We look forward to receiving your revised manuscript.

Kind regards,

Nicholas D. Duran

Academic Editor

PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: (No Response)

Reviewer #2: (No Response)

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

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4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

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PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: This is a resubmission of work investigating the role of explicit instructions on ToM (taking the partner’s perspective) in a referential communication task.

My main concern in my previous review was related to the theoretical motivation/implication. The authors have edited the manuscript, and Experiments are now more clearly motivated. The manuscript is improved by the more detailed descriptions of the experimental manipulations and analyses in the paper.

I believe the paper is much clearer now although some issues could still be made and I have a few remarks on the revised manuscript.

- Now I understand the theoretical motivation better, but the paper downplays the literature that has shown that listeners readily take the partner’s perspective in language comprehension (Hanna et al., 2003; Brown-Schmidt, 2009, etc.). There have been theoretical debates between the two groups on listeners’ ability to use common ground (Barr, 2008; Keysar et al., 1998; 2003 vs. Hanna et al., 2003; Hanna & Brenna, 2007; Brown-Schmidt, 2009); While the authors described only one side of the literature, there is a great amount of work that demonstrated that listeners could quickly identify the target based on the speaker’s perspective (Hanna et al., 2003; Brown-Schmidt, 2009; Ryskin et al., 2015, etc). I think it’s fair to introduce both sides of the literature in the introduction.

While the current work seems to be more consistent with Barr and Keysar’s claim and at odds with the results of the work by the Tanenhaus group, Arperly’s theory and the current results may contribute to reconciling the two seemingly contradictory claims. I wonder if the authors have thought about this point and if so, include it in the discussion. I bet a wider range of audiences will be interested.

- One thing I’d like to comment is that in the current study, listeners benefitted from explicit instructions, but without explicit instructions with examples, they fail to take the partner’s perspective 40-60% of the time (in E1 and E2). Even with this failure, it may not mean that listeners are not able to take the partner’s perspective; they just don’t do without specific motivation or conversational goals. In Yoon, Koh, & Brown-Schcmidt, (2012), the rate of perspective-taking varied depending on the conversational goals (instruction vs. request). Like this, participants in the “without-example” condition might be able to do so as in the explicit instruction conditions, but they might not be motivated enough – which is one of the disadvantages of non-interactive referential communication tasks (compared to interactive version). The claim in the manuscript may need to be tempered.

- pg, 12, among 96 fillers, 24 contained scalar adjectives, and 14 contained non-scalar adjectives. I guess 58 fillers were bare noun phrases (E.g., bowl). This needs to be clarified. Along with this, I have a question regarding the fillers of scalar adjectives. In Figure 1 and Table 1, I do not see any size-contrast filler items. The only size-contrast item is the critical target item (e.g., torch, present). How were scalar adjectives used to refer to filler items? Listeners are sensitive to the use of adjectives; if speakers use an unnecessary adjective, their comprehension processing might be significantly affected (e.g., when there is only one bowl, and the speaker says “move the small bowl…”).

- In Table 2, please include descriptive statistics of the control conditions. I understand the authors only analyze the critical condition in the model, but it will be helpful to understand the entire data.

- in abstract and in the intro (pg. 4), the phrase “healthy adults have little trouble understanding others’ mental states” is confusing; does it mean they do not have trouble understanding that the partner can have “different” mental state or understanding the exact different view of the partner? For example, one can know that the partner can have a different view without knowing what exactly it can be vs. one can know exactly what the partner has in his view. It needs to be clarified.

- pg. 9, Experiment 2 further investigated whether both prompts are required, and whether they need to be given sequentially. --> the later one was not tested.

- In Methods, were all participants native English speakers?

- pg. 26, line 564, “very few listeners spontaneously inferred…” This sentence is not consistent with data in E1 and E2. In Figures 2 and 3, many participants successfully take the partner’s perspective even in the “without-example” condition.

Reviewer #2: I have carefully read this revised manuscript, which I find considerably improved. You have addressed a number of my previous comments effectively, especially in terms of clarifying methodological points (e.g., how you operationalized correct responses and RTs, the rationale of your different DVs, how control and experimental trials were distributed, etc.).

I find that a few theoretical points can still be clarified further.

1. I appreciate your clarifications about the two inferential steps you identify as necessary for completing the director task successfully: (1) participants must ensure they are guided by the director’s perspective rather than their own (i.e., must inhibit their own perspective), 2. participants work out precisely how the director’s perspective constrains reference. However, I find that more work is needed to clarify these inferential processes further and strengthen the theoretical contribution of the paper.

First, I invite you to be more explicit about what step #2 involves in this director task. Specifically, I encourage you to be more specific about what you mean by “working out” how to use the director’s perspective. Is step #2 the recognition that the director cannot see items in a blocked shelf *AND* that, as a result, their intended referent of a scalar expression (e.g. “the short torch”) can be different from the participant’s?

Second, by extension, I invite you to be more explicit about how this “working out” of using the partner’s perspective can look like in other contexts involving perspective taking. Doing so can help clarify the connections between these findings and the more generalizable account you espouse, namely, Apperly’s model of mindreading (see point #2).

Third, in your response letter, you noted that you don’t consider these steps to be sequential, even though they happen to appear in sequence in the instructions. But this isn’t clearly discussed in the paper. In fact, the language used throughout the manuscript (“steps”, “inferential steps”, “chain of inference”) does suggest sequential steps. Please clarify. This is especially important because steps #1 and #2 together can result in a single heuristic for doing the task (e.g., “skip all blocked shelves”).

2. It’s not clear how the findings inform Apperly’s model of mindreading. In the Introduction you describe the two steps of the use stage of perspectival information (lines 158-165). In the Discussion you argue that your study identifies these two sub-processes of the use stage of mind reading (line 549). There’s circularity in this framing.

The most novel contribution of this work is the finding that highlighting step #1 with instructions (“inhibit your own perspective”) does not support perspective-taking performance, whereas highlighting step #2 with instructions does. This take-home message is lost a bit. This is in part because whenever the results of Experiment 1 are reported there is emphasis on the fact that that instructions with the “full chain of inferences” were required for successful perspective use. I suggest tempering these statements in your General Discussion, seeing that in Experiment 2 you actually find that an example with the full chain of inferences was not in fact required for successful performance.

Overall, I recommend highlighting your most notable contributions about the differential benefit of highlighting through instructions these two inferential steps and providing an explanatory account for this finding. That is: why is it that instructions to suppress the egocentric perspective don’t confer a performance benefit? Is it because adopting the egocentric perspective is fairly automatic and cannot be modulated by instructions? Addressing these points can bolster the theoretical contribution of the paper.

3. I don’t get the alternative account that you’re trying to rule out by testing egocentric errors past the first correct response against 0%. You argue that if participants fully understood the instructions through a more elaborated example, then floor-level error rates should be observed. I don’t see how understanding instructions obligates flawless performance. Human behavior is still replete with errors when there is response conflict, even when instructions are understood. What does “understanding instructions” mean? My general stance is that it is perfectly fine to conduct the test you did to establish that the obtained error rates are higher than zero. But I don’t see this alternative account as a plausible one that you need to rule out. If you retain this alternative account, I recommend unpacking why understanding instructions (which is different from applying the instructions) necessitates floor-level error rates.

Smaller points:

• You have changed your display in Figure 1 but, in the text, you still refer to “presents” rather than “torches” (p. 13).

• Please include in a footnote your explanation about including Bayes factors for null effects of interest.

• P. 25, bottom: You suggest that instructions “may have provided additional motivation for participants to make the required inference about using the speaker’s perspective…” This might be residual language from an earlier version of your paper. It’s not clear what you mean here about instructions serving as “motivation” or as a ‘sufficient prompt” (a few sentences below, p. 26 top).

Typos:

• P. 6, line 101: “not participants’ own perspective” --> “not the participants’…”

• P. 6, line 106: “variations of the director task has” --> have

• P. 8, line 166: “how people use mindreading information Apperly’s (2010).” ??

• P. 18, line 369: “who score highly on either autistic or psychotic characteristic”; add “an” or pluralize (“characteristics”)

• P. 20, line 422: “excluded prior analysis” --> “prior to”

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: Yes: Alexia Galati

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

23 Sep 2020

Please see attached file "Response to Reviewers"

Submitted filename: Response to Reviewer.docx

Click here for additional data file.

29 Sep 2020

Why are listeners sometimes (but not always) egocentric? Making inferences about using others’ perspective in referential communication

PONE-D-20-01714R2

Dear Dr. Wang,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

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Kind regards,

Nicholas D. Duran

Academic Editor

PLOS ONE

14 Oct 2020

PONE-D-20-01714R2

Why are listeners sometimes (but not always) egocentric? Making inferences about using others’ perspective in referential communication

Dear Dr. Wang:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

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