The influence of psychophysical procedure and stimulus type on estimates of human performance in detecting audio-visual asynchrony
Single Paper Presentation

Rob L.J. van Eijk

Armin Kohlrausch

Steven van de Par

James F. Juola

     Abstract ID Number: 43
     Full text: PDF
     Last modified: June 28, 2006
     Presentation date: 06/18/2006 4:00 PM in Hamilton Building, Foyer
     (View Schedule)

Abstract
Human perception of audio-visual synchrony 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 average of both intersections of the synchronous response curve with the non-synchronous response curve(s) 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. Two stimuli were used: (1) a flash-click stimulus, and (2) a simple animation of a bouncing ball. PSE estimates derived from synchronous-successive data were larger for the bouncing ball stimulus. Furthermore, we analysed discriminability values obtained with a 2-alternative forced-choice procedure. 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.