Studying short-term storage of expectancies with reaction time

Abstract

On each of 198 choice reaction time (RT) trials, subjects verbally predicted which of two possible stimuli would occur and then waited 3, 7, or 11 sec before receiving a ready signal and the stimulus presentation. Four groups of 20 subjects each were defined by the nature of the distractor task interpolating the time between a prediction and the ready signal. These conditions were as follows: (1) No distraction task was required, (2) the subject vocally repeated the prediction until the ready signal sounded, (3) the subject counted backward by threes until the signal occurred, and (4) the subject repeated the nonpredicted stimulus until the signal occurred. Whereas RT to incorrectly predicted stimuli did not change as a function of retention interval for any group, RT to correctly predicted stimuli increased significantly as the interval increased for the count-backward and repeat-prediction groups. For the repeatnonprediction group RT to correct predictions varied inversely with the retention interval. These results were interpreted with reference to a two-process expectancy model, short-term expectancy decay vs. interference, and negative recency effects.When subjects are required to predict the sequentially presented stimuli in a two-choice reaction time (RT) experiment, choice RT is markedly shorter when the stimulus presentation has been predicted [Le ., a correct prediction outcome (PO)] than when the stimulus has not been predicted (Le., an incorrect PO) (e.g., Bernstein & Reese, 1965;Williams, 1966). A common explanation for this PO effect is that subjects maintain an expectancy for the stimulus predicted and process expected events faster than unexpected events (cf. Geller, 1974; Hinrichs & Kranz, 1970). Supporting this simple expectancy interpretation of the PO effect are the observed relationships between choice RT and factors that presumably qualify the subject's stimulus predictions. For example, choice RT to correctly predicted stimuli was an inverse function of the confidence associated with the prediction , the probability of a correct prediction (Geller, 1974;, and the relative frequency of the stimulus predicted (e.g., Geller & Pitz, 1970; Geller, Whitman, Wrenn,& Shipley, 1971).The present research was designed to follow up an observation that the PO effect decreased as the interval between th~ subject's prediction and the stimulus presentation mcreased (Geller & Whitman, 1972). In the Geller and Whitman study, the prediction-to-stimulus (P-S) interval was 3, 7, or 11 sec, varying randomly among the 198 trials for each subject. Geller and Whitman referred to differential short-term storage of expectancies in order to interpret their rmding that RT to correctly predicted stimuli was a direct function of the Reprints are available from the author, Department of Psychology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061.Copyright 1982 Psychonomic Society, Inc. 3 P-S interval and RT to incorrectly predicted stimuli varied inversely with the P-S interval. Thus, th...