Older age results in difficulties separating auditory and visual signals in time

Previous research provides conflicting evidence regarding whether older adults have altered tolerance to timing differences between auditory and visual events. We examine the potential impact of age-related unisensory decline on audiovisual synchrony perception. Fifteen younger (21-32 years) and 13 older (60-72 years) adults participated. To assess unisensory sensitivity, visual Gabor contrast detection thresholds and auditory masked tone pip detection thresholds were measured. Four multisensory conditions were then tested: suprathreshold and near-threshold stimuli (based on individual unisensory psychometric functions), each tested with a masked tone pip stimuli at 0.5 and 4 kHz sound frequencies. Two audiovisual pairs (one synchronous, the other asynchronous) were presented in a two-interval forced-choice procedure, with observers identifying the interval containing the asynchronous stimulus. Older adults required a larger physical asynchrony to perceive the stimuli as asynchronous, particularly for low frequency sounds. Our results demonstrate that the impact of age on audiovisual synchrony perception cannot be explained by decline in unisensory sensitivity alone.