Charles P. Whitman

Confidence ill stimulus predictions and choice reaction time

In two choice reaction time (RT) experiments, a stimulus prediction and a confidence judgment in the prediction preceded each occurrence of one of two stimulus alternatives. Ss identified each stimulus presentation by pressing a left-hand or right-hand telegraph key. In Experiment I the source of the stimulus predictions and confidence estimates was varied between groups of 20 Ss. For each condition, RT to correctly predicted stimuli was an inverse function of prediction confidence. Following incorrectly predicted stimuli, RT was not reliably influenced by confidence when S gave both predictions and confidence judgments; but RT to incorrectly predicted stimuli was an increasing function of confidence when E verbalized the predictions and confidence estimates or when S predicted and E indicated confidence. In Experiment II Ss made predictions and the validity of Es confidence estimate was manipulated between Ss. When Es confidence was perfectly related to the probability of a correct prediction, choice RT to nonpredicted stimuli was inversely related to confidence. However, choice RT to nonpredicted stimuli was not affected by prediction confidence when Es judgments were random.

Stimulus probability and prediction outcome as determinants of choice reaction time: Some procedural considerations

Abstract Effects of stimulus probability and prediction outcome on two-choice reaction speed (CRS) were determined when a frequency imbalance was reversed half-way through 300 samples of a 70/30 stimulus distribution and when the same 70/30 distribution was sampled for 1200 trials. Prior to each presentation S s made a prediction; following each presentation S s identified the stimulus by pressing a right-hand or left-hand trigger. CRS was faster to correctly predicted stimuli, and faster to the more probable stimulus. S s who were informed of the frequency imbalance reacted significantly faster than S s who were not. Both practice and boredom effects were demonstrated by using the extended number of trials. CRS was faster during the second session of 300 trials than during the first; after two sessions, CRS was slower during the second half of two additional sessions.

Runs of correct and incorrect predictions as determinants of choice reaction time

Intrasequential effects of prediction outcomes on choice reaction speed (CRS) were studied in a two-alternative reaction task. Prior to each of 300 stimulus presentations, Ss predicted the next stimulus; following each presentation, Ss identified the stimulus by pressing one of two reaction triggers. Not only was CRS faster to predicted than nonpredicted events, but given a correctly or incorrectly predicted event, CRS was significantly faster when the preceding prediction outcomes were correct than when they were incorrect. The implications of these results for dichotomous and continuous notions of expectancy are discussed.

Manipulation and reversal of the probability of a correct stimulus prediction in a choice reaction task

In a two-stimulus, two-response choice reaction time (RT) experiment, the probability of a correct stimulus prediction was controlled: the probability (P) was.70 or.30 for 400 trials or P was.70 or.30 for 200 trials and 1 — P for the remaining 200 trials. The difference between RT to correctly predicted stimuli and RT to incorrectly predicted stimuli was greater when P was.70 than when it was.30. When P shifted from.30 to.70, the effect of prediction outcome increased; the effect of prediction outcome decreased when P shifted from.70 to.30. Implications for learning in the development of expectancies for predicting correctly are discussed.

Effects of expressed and measured value preference on decision speed

Decision speed was studied as a function of value preference determined by a subjective and a measured ranking of the six value areas of the Allport-Vernon-Lindzey Study of Values (AVL). Ss were sequentially presented with a list of 180 value-related words and were required to categorize each word into one of the six AVL value areas by pressing one of six decision levers. The latency between each stimulus presentation and the decision response was measured without Ss knowledge. Decision speed was significantly influenced by practice and personal value preference. For each method of determining value rank, an inventory (AVL profile) and a subjective (introspective ranking) technique, the relationship between speed and value rank was generally U-shaped (i.e., words representing the most and least preferred value areas were categorized fastest).