In 6 experiments, the authors investigated the form of serial position functions for identification of letters, digits, and symbols presented in strings. The results replicated findings obtained with the target search paradigm, showing an interaction between the effects of serial position and type of stimulus, with symbols generating a distinct…

Although a feature detection theory of pattern recognition is consistent with many recent physiological findings, the specific rules governing the perception of the distinctive features of letters have not yet been determined. This article presents two new experimental procedures for determining these rules. (Editor)