Bisensory vs summed-unisensory improvement on two speech-reception tasks

It is known that in speech reception tasks, when performance scores in the auditory-only (A) mode and the visual-only (V) mode are simply added, the result will be substantially less than when eyes and ears can simultaneously process the stimuli (A/V mode). However, it is not known whether the improvement with practice and/or training with feedback is greater in the A+V or the A/V mode. Normal young adults (N:20) watched and listened in the A/V mode and responded to 100 key words in sentences spoken by a man on a 25-inch color TV at a distance of 6 ft, both before and after training with feedback on other lists of 100 key words. In the training condition, half the Ss were given the A mode first, half the V mode. Within the training condition, pre- and post-training test phases of 100 key words each had a training phase intervening in which feedback was given on 100 different key words. Performance significantly improved from 28.8% to 35.0% words correct within the training condition, averaged over A and V mode (6.2%; p less than .001), but it improved from 68.5% to 86.0% (= 17.5%; p less than .001) in the pre- vs post-training comparison for the A/V mode. The difference of 11.3% in favor of the A/V mode was significant (p less than .01). Essentially zero correlation was found between individual improvements in the A+V vs the A/V mode. The acquisition and utilization of A, V, and A/V skills are independent and specific. Each mode may have its optimum set of training conditions.(ABSTRACT TRUNCATED AT 250 WORDS)