Abstract
Exposure to a stream of temporally offset visual and auditory signals changes an observers' perception of synchrony. Previous literature suggests that adapting to audiovisual temporal offsets is needed to correctly combine audiovisual stimuli into a single percept for a range of source distances. Older people have wider synchrony windows, i.e. are more likely to perceive synchrony for visual and sound signals with larger temporal offsets. The impact of ageing on audiovisual recalibration is unclear. Audiovisual synchrony perception for sound-lead and sound-lag stimuli was measured for fifteen younger (22-32years old) and fifteen older (64-74years old) adults using a method-of-constant-stimuli, after adapting to a stream of visual (Gabor, 10ms, 3c/deg, 85% contrast) and auditory (20dB, 10ms tone pip increment on a 75dB, 1100ms tone mask, both at 500Hz) pairs. The adaptation pairs were either synchronous or asynchronous (sound-lag of 230ms). Individual data were fitted with two Gaussian functions where window width was defined as the difference between the means of the functions fitted to the sound-lead and sound-lag conditions. The adaptation effect for each observer was computed as the shift in the mean of the fitted psychometric functions after adaptation to asynchrony. Post adaptation to synchrony, the younger and older observers had average window widths (±standard deviation) of 326(±80) and 448(±105)ms, respectively. After adapting to asynchrony, there was no adaptation effect for sound-lead pairs. The younger and older observers however perceived more sound-lag pairs as synchronous (shift in psychometric function of 94(±55) and 20(±41)ms respectively: RM-ANOVA: interaction between age and adapted condition for perceived sound-lag asynchrony (F(1,28)=16.78, p<0.001). The magnitude of the adaptation effect in the older observers was not correlated with their thresholds for asynchrony for sound-lag stimuli (Spearman's rank order correlation: rs(13)=-0.064, p=0.82). These findings show that the audiovisual synchrony window is less adaptable with age.
Meeting abstract presented at VSS 2014