Spatial Congruity in Audiovisual Synchrony Judgments

Rainer Guski Dept. of Psychology, Ruhr-University Bochum, Germany [email protected] Abstract The systematic analysis of the perception of audiovisual synchrony has shown that auditory delays are tolerated to a certain extent in synchrony judgments, but the variation of spatial separation between light and sound has brought conflicting results: While Lewald & Guski (2003) did not find a significant influence of spatial separation in synchrony judgments, Spence et al (2003) did find one in temperal order judgments. This may be due to methodological differences between synchrony and temporal order judgments, but it may also be due to spatial congruity, which was randomized by Lewald & Guski, and was confounded with spatial separation by Spence et al. (2003). The present contribution asks if audiovisual synchrony judgments are influenced (1) by the sound reproduction system, and (2) by the spatial congruity of light and sound. The results of an experiment are presented that asks participants for quick Yes/No-Responses with repect to audiovisual synchrony and varies systematically three factors: (a) the audiovisual synchrony (-250 to +250 ms), (b) the sound reproduction system (earphones vs. loudspeakers), and c) the spatial congruity (left and right) of light and sound stimuli. The results do not show a systematic influence of spatial compatibility of the audiovisual stimuli on raw synchrony judgments. . Introduction Audiovisual judgments of synchrony or temporal order depend on a number of influences,e.g. the type of stimuli used (with speech producing greater just noticeable differences (JNDs) than abstract stimuli), the type of task (with synchrony judgments (SJ) producing greater JNDs than temporal order judgments (TOJ)). The spatial separation between light and sound is also claimed to have an influence (Bertelson & Aschersleben 2003; Spence et al. 2003; Spence & Read 2003; Zampini et al. 2003a,b), but Lewald & Guski (2003) did not find a significant influence of spatial separation on synchrony judgments. The difference between results fromdifferent laboratories may be due to methodological differences between synchrony and temporal order judgments, but it may also be due to spatial congruity, which was randomized by Lewald & Guski (2003), and was confounded with spatial separation by Spence et al. (2003). The present contribution asks whether audiovisual synchrony judgments and decision times for these judgments are influenced by the spatial congruity of light and sound.