Order-relevant and order-irrelevant decision rules in multiletter matching.

Two experiments examined order effects in multiletter matching. In each experiment, subjects used one of two decision rules that differed in whether pairs of letter strings that contained the same letters, but in different orders (rearranged pairs), were classified as same or different. Method of presentation also was varied, with the two strings in each pair being presented either simultaneously or successively in one experiment, and with the exposure duration of the second of two successively presented strings being either short or long in the other. Latency and accuracy of responding to the rearranged pairs varied as a function of the amount of positional displacement, with the two tasks showing similar, but mirror image, patterns. This outcome suggests that most of the order effects are attributable to processes common to both tasks, although there was some evidence for a contribution from task-specific processes as well. Both method-of-presentation manipulations had little influence on the order effects, suggesting that the effects are attributable to perceptual and decision processes, rather than to memory processes. The results are most consistent with a model that assumes position-sensitive comparisons, with the same-different decision based on pooled information.