McCarthy and Donchin (1981) found that the latency of a late positive component of the event‐related potential (ERP) was influenced by the presence of noise in a stimulus matrix but not by the compatibility between the stimulus presented and the response required. They concluded that this component is a P300 and that its latency was influenced by stimulus evaluation but not by response selection processes. The present experiments were designed to confirm that the component identified by McCarthy and Donchin was indeed a P300 and to determine if its latency varies systematically with increases in stimulus evaluation time produced by graded changes in noise level. In Experiment 1, subjects performed a standard oddball task in which they were required to count the rarer of two stimuli (the words RIGHT or LEFT) which were, or were not, embedded in a noise matrix (characters from the alphabet). The positive component of the ERP, whose amplitude was larger for rare target stimuli, was labeled a P300, and the latency of this component was longer when the stimuli were embedded in noise. In Experiment 2, subjects performed a choice reaction time task. Following the procedures used by McCarthy and Donchin, stimulus words RIGHT and LEFT required right or left hand responses depending on the presence of a cue word SAME or OPPOSITE which preceded the stimulus. Stimulus words were presented in four different degrees of noise, the levels of which were manipulated by varying the set size of the alphabetic characters which could surround the stimulus words. Reaction time increased both with noise (by 325 ms) and as a function of stimulus‐response incompatibility (by 127 ms). In contrast, P300 latency increased substantially with noise (by 200 ms) but, to a much lesser extent (by 14 ms), with response incompatibility. These results indicate that the P300 is sensitive to the ease with which a target stimulus can be discriminated from noise. They confirm that P300 latency can be used as a measure of the timing of stimulus evaluation processes that is relatively independent of response selection and execution.
Two experiments are reported in which the spacing between pairs of identical (Experiment 1) or pairs of related (Experiment 2) to-be-remembered words were varied while pupil diameter and frequency judgments were measured. In Experiment I, frequency judgments increased with increases in spacing length. In Experiment 2, frequency judgments decreased with increases in spacing length. In both experiments, however, pupil dilations increased with increases in spacing length. These results are interpreted as supporting theories that argue that massed repetitions require less processing than spaced repetitions. It is argued that this deficiency in processing reduces retention of massed repetitions of identical words. For massed presentation of related words, organizational strategies can be used with little effort to increase retention.A common finding in memory research is that spaced repetitions of to-be-remembered words result in better retention than do massed repetitions. Many theories have been proposed to account for the spacing effect, but none has received a consensus of support. Several accounts of the spacing effect propose that massed repetitions receive less processing than do spaced repetitions. Underwood (1969) suggested that massed repetitions are not attended to as well as spaced repetitions. Shaughnessy, Zimmerman, and Underwood (1972) tested this voluntary-attention explanation of the spacing effect by allowing subjects to control the time spent studying each to-be-remembered item. They found that repeated items were given less study time when the repetitions were massed than when they were spaced. Damaging evidence against the voluntary-attention hypothesis, however, was produced by Hintzman, Summers, Eki, and Moore (1975). In Experiment I, they paired some of the repeated items with an incentive tone signaling high payoff for later retention. The incentive tone elevated frequency judgments at all spacings, but the spacing effect was the same in the notone and the tone conditions. In Experiment II, subjects studied some lists aloud by reciting each word three times. Again, this failed to attenuate the spacing effect This paper is based on a dissertation submitted to the U niversity of Texas at Arlington in partial fulfillment of the requirements for the PhD degree. I would like to express my gratitude to James R. Erickson, Ira H. Bernstein, Robert J. Gatchel, James N. Bowen, and Raymond 1. Jackson for support and guidance. Additional thanks are extended to Edward Shoben for reviewing an earlier version of the manuscript, to EllenGorthey, Beth Huggins, Cheryl Buckner, and ElizabethGaasfor assistance in data collection and scoring, and to Betty Bilotta for typing. Requests for reprints should be sent to the author at Applied Science Associates, Inc., P.O. Box 158, Valencia, Pennsylvania 16059.(compared with a silent study condition). The final experiment measured eye fixations to pictures and found no effect of spacing length. The three experiments, then, produced no support for a voluntary-attention ...
Two experiments are reported in which a reduction in tone intensity or duration followed habituation. Experiment I, which employed 120 subjects, assessed the effects of type of stimulus change (intensity or duration) and trial of change (trial 5 or trial 22) on orienting response (OR) recovery. Experiment II employed 131 subjects, and examined the effects of reduction of stimulus intensity on trial 22 or after subjects reached a predetermined habituation criterion. Experiment I demonstrated OR reappearance following the offset of a shortened stimulus. The combined findings of Experiments I and II suggest that the effects of reducing stimulus intensity depend on when the change is made. In Experiment I, reducing stimulus intensity on trial 5 led to a significant decrease in OR magnitude. In Experiment II, increases in OR magnitude were produced by reducing stimulus intensity either after reaching a criterion or after 21 habituation trials. These findings suggest a Sokolovian view of the development of the generalization gradient of habituation. Results also revealed large individual differences in responding to the stimulus change in Experiment II. Multiple regression analyses of these data were therefore conducted, which allowed two further conclusions to be drawn: First, initial electrodermal state can be used to predict responding on the stimulus change trial. Second, with long habituation training (21 trials), the role of the initial state variables diminishes while other variables representing change over the experimental session become more prominent in predicting responding to stimulus change.
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