A theory of perceptual matching.

When two patterns are compared, same judgments typically are faster than different judgments. This result is perplexing because same, but not different, judgments would seem to require full and exhaustive processing. Some models have depicted same processing as more efficient or powerful than different processing due to an identity reporter or to priming. When accuracy rather than reaction time (RT) is examined, however, same processing looks generally less efficient than different processing: Subjects are more likely to make false different responses to same pairs than false same responses to different pairs. The present noisy-operator theory holds that internal noise is more likely to produce spurious featural mismatches than matches and that the rechecking needed to remove these spurious differences produces the typically longer RT for different judgments. Data from comparisons of single-patter n (Cases 1, 2, and 3) or multiletter strings (Cases 4, 5, and 6) were fitted to a single-processor accumulative model based on the theory. This report deals with a deceptively simple task. A person is shown two patterns, either side by side or one after the other, and must decide as rapidly (and accurately) as possible whether they are identical or not. Trials are randomly intermixed, of course, so that the subject never knows beforehand whether he will see a same or different pair. The matching processes involved in this simple task are im