ENHANCEMENT OF PERCEIVED VISUAL INTENSITY BY AUDITORY-STIMULI - A PSYCHOPHYSICAL ANALYSIS

Judgments of the intensity of a stimulus are dependent on the level of central nervous system activity it generates. Generally, it is assume d that such judgments are based on activity along modality-specific pa thways. Thus, visual intensity judgments would be based on unimodal vi sual activity. However, many neurons do not fit neatly within modality -specific categories, but can be influenced by more than one sensory m odality. Often the ''multisensory'' effect is quite pronounced. If the se multisensory neurons participate in such fundamental functions as p erceived intensity, the presence of a nonvisual (i.e., auditory) cue m ay have a significant effect on the perceived intensity of a visual cu e. The results of the present study were consistent with such a hypoth esis. A brief, broad-band auditory stimulus was found to significantly enhance the perceived intensity of an LED. The effect was most pronou nced at the lowest visual intensities, and was evident regardless of t he location of the auditory cue. However, it was present only at the l ocation of visual fixation. Yet, despite the significant influence of the auditory cue, and its differential effect at different visual inte nsities, a power function that maintains the proportionality among per ceived visual intensities was retained.