CONJOINING AUDITORY AND VISUAL FEATURES DURING HIGH-RATE SERIAL PRESENTATION - PROCESSING AND CONJOINING 2 FEATURES CAN BE FASTER THAN PROCESSING ONE

The time required to conjoin stimulus features in high-rate serial pre sentation tasks was estimated in auditory and visual modalities. In th e visual experiment, targets were defined by color, orientation, or th e conjunction of color and orientation features. Responses were fastes t in color conditions, intermediate in orientation conditions, and slo west in conjunction conditions. Estimates of feature conjunction time (FCT) were derived on the basis of a model in which features were proc essed in parallel and then conjoined, permitting FCTs to be estimated from the difference in reaction times between conjunction and the slow est single-feature condition. Visual FCTs averaged 17 msec, but were n egative for certain stimuli and subjects. In the auditory experiment, targets were defined by frequency, location, or the conjunction of fre quency and location features. Responses were fastest in frequency cond itions, but were faster in conjunction than in location conditions, yi elding negative FCTs. The results from both experiments suggest that t he processing of stimulus features occurs interactively during early s tages of feature conjunction.