Can we see and hear at the same time?. Some recent studies of intersensory facilitation of reaction time

Visual reaction time is facilitated by a simultaneous auditory event. This finding poses a problem for proponents of a single channel theory of attention since the auditory and visual events should be mediated by different input channels, only one of which is accessible to attention and processing at a time. In order to reconcile this discrepancy with single channel theory, two logically independent models were adduced, both of which assume a non-attentional parallel pathway with properties similar to those ascribed to the recticular formation. The first, or energy integration model, assumes that stimulus intensities may add across modalities causing the joint event to be effectively stronger than the visual event alone. The second or preparatory state model assumes that response preparation, defined as a generalized disposition to make an overt response regardless of the specific nature of the response, may proceed in parallel with specific stimulus and response selection and may be initiated by non-attended stimuli. Evidence was found in separate studies to support both models.