More of me! Distinguishing self and reward bias using redundancy gains.

Participants show a perceptual bias favoring stimuli associated with the participants themselves over stimuli associated with other people. A major account of this self-bias effect is that self-related information is intrinsically rewarding, and that high-reward stimuli have enhanced perceptual processing. Here we used redundancy gains to examine the relations between self bias and reward, and whether self and reward biases modulate common levels of stimulus integration. We demonstrated that the self-association bias increases when more than one exemplar of the stimulus is presented (i.e., when participants are exposed to redundant stimuli). The larger self-bias effects for redundant than for single stimuli arose at both perceptual and conceptual levels of representation (respectively, for identical and nonidentical stimuli associated with the same category). In contrast, high-reward stimuli did not affect perceptual redundancy gains with identical shapes, but they did affect redundancy gains with nonidentical stimuli associated with the same category. The strong redundancy effects with self-related stimuli are consistent with self associations modulating stimulus integration at both perceptual and conceptual levels, whereas reward only modulated higher-level conceptual processes (with nonidentical stimuli). The data provide two novel theoretical advances, by showing that (i) self association modulates both early perceptual coding and higher-level conceptual coding, whereas reward only affects the higher-level process, and (ii) self bias can not be reduced simply to differential effects of reward.