The perceived timing of events across different sensory modalities. A psychophysical investigation of multisensory time perception in humans.

Abstract

The experiments reported within this thesis use psychophysical techniques to examine the factors which determine perceived multisensory timing in humans. Chapters 1 and 2 describe anatomical and psychophysical features of temporal processing, respectively, whilst Chapter 3 introduces the reader to psychophysical methods. Chapter 4 examines the relationship between two measures of sensory latency, reaction time (RT) and crossmodal temporal order judgment (TOJ). Despite task and attentional manipulations the two measures do not correlate, suggesting that they measure some fundamentally different aspect(s) of temporal perception. Chapter 5 examines the effects of adaptation to asynchronous stimulus pairs on perceived audiovisual (AV), audiotactile (AT) and visuotactile (VT) temporal order. Significant temporal shifts are recorded in all three conditions. Evidence is also presented showing that crossmodal TOJs are intransitive. Chapter 6 shows that concurrent adaptation to two sets of asynchronous AV stimulus pairs causes perceived AV temporal order to recalibrate at two locations simultaneously, and that AV asynchrony adaptation effects are significantly affected by observers¿ attention during adaptation. Finally, Chapter 7 shows that when observers are accustomed to a physical delay between motor actions and sensory events, an event presented at a reduced delay appears to precede the causative motor action. The data are well-described by a simple model based on a strong prior assumption of physical synchrony between motor actions and their sensory consequences.