The influence of psychophysical procedure on estimates of human performance in detecting audio-visual asynchrony

Rob L.J. van Eijk, Human-Technology Interaction, Eindhoven University of Technology

Abstract
Human performance in audio-visual synchrony perception is typically characterized by two quantities: the point of subjective equality (PSE) and human sensitivity to asynchrony. The PSE can be derived from the 50% point in a temporal order judgment (TOJ) procedure or from the maximum synchrony response in a synchronous-successive response paradigm. Sensitivity is derived from the steepness of the response curve in the TOJ paradigm. In this contribution we present data that show that PSE estimates derived from TOJ measurements are much more variable across observers than those based on synchronous-successive data. Two synchronous-successive methods were used with different response categories: (1) 2 categories: asynchronous, synchronous, and (2) 3 categories: audio first, synchronous, video first. Both synchronous-successive methods yielded similar results. Furthermore, we compare discriminability values derived from TOJ and synchronous-successive curves with values obtained with a 2-alternative forced-choice procedure. Results indicate that discriminability is better near the edge than in the middle of the synchronous response category. This suggests that categorical perception might play a role in audio-visual synchrony perception.

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