Abstract
We investigated differences in the point-of-subjective simultaneity (PSS) and temporal integration window (TIW) across audiovisual stimulus type and task (van Eijk et al., 2008). Participants (n = 28) completed two tasks in separate blocks, 1) in synch or out of synch - synchrony judgment task (SJ), 2) visual or auditory first - temporal order judgment task (TOJ). Five stimulus types were used: point-light-drumming (PLD), audiovisual speech (FV), single beep-flash (BF), single beep-flash with constant visual information (BFV), and beep-flash sequence with the timing properties of PLD (BFD). Each was presented at one synchronous and 10 asynchronous levels (5 audio-leading, 5 video-leading). Best-fitting Gaussian curves to the number of synchronous and visual first responses were calculated for SJ and TOJ data, respectively. PSS was derived as the peak of the SJ curve and the 50% point of the TOJ cumulative curve. TIW was taken as the standard deviation of the Gaussian curve for each task. Visual inspection of fits revealed that, 1) no participants managed to do TOJ for BFD stimuli; 2) less than 50% could do TOJ on complex stimuli (FV and PLD); 3) ~90% were able to do TOJ on BF and BFV stimuli; 4) ~85% were able to do SJ for all stimuli. Interestingly, PSS for SJ were all video leading, regardless of stimulus type, while they were all audio leading for TOJ, in line with previous research (Petrini et al., 2010). Using only participants able to do SJ for all stimuli (n = 23) we conducted one-factor ANOVAs on PSS and TIW data. Stimulus type influenced both PSS (F(88,4) = 11.363, p < 0.001) and TIW (F(88,4) = 23.837, p < 0.001). Only four subjects were able to do the TOJ on all stimulus types (excluding BFD). Overall, TOJ is a harder task than SJ; both PSS and TIW differed as a function of stimulus type and tasks.
Economic and Social Research Council.