Simultaneous processing of verbal and spatial information.

Two experiments investigated the generality of the selective interference phenomenon by studying several different concurrent tasks, each involving either verbal or spatial information, and a range of retention intervals from 10 to 30 sec. The results supported the selective interference predictions, since the interference in performance was greater when the two simultaneous tasks both involved either verbal information or spatial information than when one of the tasks involved verbal and the other spatial information. It was concluded that not only was the selective interference phenomenon a rather general effect but that, since it was unaffected by changes in the nature of the component tasks, it was also probably caused by central processing capacity limitations rather than by competition for a specific structural mechanism.