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Abstract

Studied the effects of stimulus modality and stimulus spacing on duration classification in the human temporal bisection task. Two experiments were run with a total of 32 Ss. The 1st experiment tested only a single modality (visual or auditory), while the 2nd tested both modalities. When auditory and visual signals were presented in the same test session, visual signals were judged shorter than auditory signals that had equivalent durations, but, when subjects were exposed to a single modality within a session there was no difference between auditory and visual signal classifications. The authors suggest a model in which visual and auditory signals evoke different variable memory representations for the same objective-time duration signal. This difference is revealed only when subjects experience both modalities in the same session and the memory for the target duration is a mixture of representations generated on both auditory and visual trials. The authors also apply this memory mixing notion to the stimulus spacing literature as one possible mechanism that can account for the difference in psychometric functions when stimuli are either logarithmically or linearly spaced.