Auditory manipulation of visual perception

Psychological research on cross-modal auditory-visual perception has focused predominantly on the manipulation of sensory information by visual information. There are relatively few studies of the way auditory stimuli may affect other sensory information. The Sound-induced Illusory Flash is one illusory paradigm that involves the auditory system biasing visual information. However, little is known about this cross-modal illusion. More research is needed into the structure of the illusion that investigates the different conditions under which the Sound induced Illusory Flash manifests and is enhanced or reduced. The research conducted for this thesis investigates the effect of new auditory stimulus variables on the Sound-induced Illusory Flash. The variables to be discussed concern the formation of a contrast in the auditory stimuli, with the contrast creating a rhythm that emphasises the discontinuous nature of the auditory stimuli, and therefore emphasises the illusory percept. The auditory stimulus contrasts include pitch separation with the octave interval, using the frequencies of 261.5 and 523Hz; and spatial separation in the auditory stimuli, presenting the monophonic auditory stimuli binaurally so that individual tones alternate between the left and right channels. I furthered this concept of auditory stimuli separation biasing an illusory percept, by investigating pitch and spatial presentation and localisation of the visual stimuli presentation, when multiple dots were presented. I also conducted analyses to determine if factors other than the auditory stimuli biased the illusory percept. These included the use of non-illusory trials and determining if their inclusion biased the illusory trial percept; and the impact of physical factors such as handedness, eye dominance, corrected vision, and musical experience on the illusory percept. My ultimate aim is to develop the illusory effect as a basis for new intermedia techniques to create the perceptual synchronisation of sound with images. These would be perceived as visually spliced according to the rhythm of the music on the micro time scale