The effect of stimulus frequency, spectrum, duration, and location on temporal order judgment thresholds: distribution analysis.

The present study aimed to examine whether the judgments of temporal order are made by the same "central processor" regardless of the characteristics of the sound stimuli. The influence of stimulus parameters (e.g., frequency, spectrum, duration, location) on auditory temporal order judgment (TOJ) thresholds was tested in seven groups with a total of 192 participants received two-tone sequences of different: frequencies (3 groups); spectrum widths, via a pure tone and a Gaussian noise burst (1 group); durations (2 groups); or locations, via asynchronous presentation to each ear (1 group). No difference in the mean rankings of TOJ thresholds was found for frequency, spectrum, and location parameters. TOJ thresholds for the duration condition, however, were significantly longer than for any of the other conditions. Notably, the threshold distributions for all the parameters (frequency, spectrum, duration, location) differed in shape. These findings raise the question as to whether we can rely upon the mean or median threshold as truly representative of TOJ threshold data. Furthermore, the data suggest that temporal order judgments for the different stimulus parameters are processed differently. The differences observed when analyzing the data with central tendency measures, as compared to analyzing the threshold distributions, may explain some of the mixed results reported in the literature on the mechanisms involved in temporal processing of different parameters. Stimulus parameters influence TOJ threshold distributions and response patterns, and may provide additional cues, beyond the standard temporal cue inherent in the TOJ procedure, by which participants may judge the order of the stimuli.