A two-factor theory of stimulus-repetition effects

It is a well-documented finding that children respond more slowly to a stimulus that has been presented repeatedly just before test than to a novel stimulus. The effect, for which a two-factor theory has recently been proposed, did not occur in the only previous study of adults using a comparable procedure. Experiment 1 demonstrated the effect with adults. The previous negative finding may have been the result of too few repetitions of the stimulus. Experiment 2 provided additional support for the two-factor theory. The theory suggests that the effect is the net result of partially counteracting changes in two attentional processes. One process, the alertness elicited by a stimulus, is held to decrease as a result of repeated presentation of the stimulus, while the second process, encoding, is facilitated. The hypothesis tested in Experiment 2 was that the alertness decrement dissipates over a brief passage of time, while the facilitation of encoding does not. Subjects exposed to a repeatedly presented color were tested either immediately thereafter or after a 15-min or 30-min interval. As predicted, the observed effect shifted from one of flower response to one of faster response to the repeated stimulus as the delay interval increased.