Sequential search processes in long-term memory

In an experiment employing the symbol-element recognition task (Mohs, Wescourt, & Atkinson, 1975), subjects first learned six lists consisting of four words (elements) each. Each list was associated with a unique consonant (symbol). Subsequently, on each of a series of test trials, subjects were presented with one, two, or four symbol-element pairs. A positive response was required if all test words were correctly paired with their associated consonants and a negative response if any one test word was incorrectly paired with a consonant. Of primary concern was the way reaction time (RT) varied with number of pairs presented, the type of response required, and, on negative trials, the position of the mismatched pair in the test display. RT increased with the number of pairs presented on a trial and the increase was greater for positive than for negative trials. For negative pair trials, RT increased with the distance of the mismatched pair from the top of the test display. On negative trials in which the top pair in the test display was the mismatched pair, RT increased with the total number of pairs presented on the trial. A serial, probabilistic order of processing model is proposed to account for these results, and applications of the model to other paradigms are discussed.