Searching for many targets: An analysis of speed and accuracy

Three Ss scanned matrices of letters for 40 sessions in a test of Neisser's claim that feature tests in high-speed searches operate independently and in parallel. In the multiple-target condition (MTC), the matrix contained any one of four target letters, while in the four single-target conditions (STC), the S knew which particular target was embedded in the list. In contrast to previous studies, the error rates for individual target letters in the MTC were analyzed separately rather than being pooled. Two Ss made more errors on the hardest target when searched for in the MTC than in the STC. This difference would be masked by pooling error rates. The third S's scanning rate in the MTC was not as rapid as in the STC. Neither a sequential nor a strictly parallel feature processing model can account for these data.