Probability discrimination indicated by stimulus prediction and reaction speed: Effects of S-R compatibility.

Perception & Psychophysics

1977

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Following each of 400 stimuli that varied according to three binary dimensions (location, color, and shape), subjects named the value of one particular dimension as quickly as possible. Each stimulus appeared on the "left" and "right" side of a screen (location dimension), and was a "red" or "green" triangle (color dimension) with apex oriented "up" or "down" (shape dimension). The alternatives of each dimension varied according to different probability distributions (90/10, 70130, or 50/50), and three schedule conditions were contrived so that each distribution occurred once for each dimension. Nine groups of 10 subjects each defined the factorial of 3 (response conditions: identify location, color, or shape) by 3 (schedule conditions: 90 left/70 red/50 down, 70 left/50 red/90 down, or 50 left/90 red/70 down). Latencies to identify the shape dimension were influenced reliably by the probabilities of both response-relevant and responseirrelevant stimuli. Shape probabilities did not affect latencies to identify location of color, but these latencies were significantly influenced by both color and location probabilities. Results are discussed with reference to the locus of the stimulus probability effect and dimensional integrality.Perhaps the most common finding when measuring latencies between stimulus presentations and identification responses is that choice reaction time (RT) is significantly shorter to more frequently occurring stimuli. The phenomenon has been termed a "stimulus probability effect" (SPE); and although the SPE has been consistently observed, interpretations of the cognitive locus of the phenomenon have not been consistent. Specifically, some RT investigators have claimed that the SPE is largely a responsebias effect, resulting from differential response selection (e.g., Theios, 1973Theios, , 1975, whereas others have presumed that variations in stimulus frequency affect primarily the stimulus-encoding stage of information processing (e.g., Pachella, 1974;Pachella & Miller, 1976). The present RT experiment was partially designed to study the relative importance of stimulus-encoding processes in determining the SPE.Three general techniques have been used to compare the relative influence of stimulus and response processing in determining the SPE: (1) threestimulus, two-response paradigms, (2) additivefactor designs, and (3) S-R compatibility manipulations. Although a given experiment has often showed Portions of this paper were presented at the Midwestern Psychological Association meeting, Chicago, 1975. Requests for reprints should be sent to E. Scott Geller, Department of Psychology, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061. 70one information-processing component to be the more significant determinant of the SPE, the particular component judged to be the prominent factor has varied between experiments. For example, when RT was faster to the more probable of two stimuli identified with the same response, Bertleson and Tisseyre (1966) concluded that stimul...

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confidence: 99%

Latencies to name one of three stimulus dimensions: A study of probability effects and dimension integrality

Perception & Psychophysics

1977

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“…One of their basic assumptions was that Ss' expectancy for a correctly predicted stimulus was a direct function of Ss' confidence that their stimulus prediction would be correct. Thus, the results of recent choice RT experiments were explained by assuming Ss' confidence in a prediction to be greater when the more probable stimulus was predicted (Geller, Whitman, Wrenn, & Shipley, 1971;Geller et al, 1972) and when the immediately preceding prediction had been correct .…”

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confidence: 99%

“…Choice reaction time (RT) experiments in which Ss predict which stimulus will occur prior to a stimulus presentation have demonstrated reliably shorter latencies to correctly anticipated stimuli and to the more probable of two stimuli (e.g., Geller, Whitman, & Farris, 1972;Hinrichs & Craft, 1971;. A model which has been used to explain the independent effects of stimulus probability and prediction outcome on choice RT was derived from the continuous expectancy notions of Geller and Pitz (1970).…”

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confidence: 99%

Prediction outcome probabilities as determinants of choice reaction time

Whitman

Perception & Psychophysics

1973

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In a two-stimulus two-response choice reaction time (RT) task in which Ss made stimulus predictions, the probability of a correct prediction was manipulated between Ss. The magnitude of the difference in RT to correctly and incorrectly predicted stimuli (i.e., the prediction outcome effect) was an increasing function of the probability of a correct prediction. This finding was primarily due to a reliable decrease in RT to correctly predicted stimuli as the probability of a correct prediction increased, since RT to incorrectly predicted stimuli was not affected by prediction outcome probability. These results were interpreted as partially supporting a continuous expectancy notion which involves facilitory and inhibitory mechanisms which are differentially influenced by the probability of a correct prediction.

“…For example, a continuous effect of probability on two-choice RT may have occurred when the probability effect (i.e., faster responses to the more probable stimulus) was an increasing function of the extent of the frequency imbalance between the stimuli of different sequences (Hinrichs & Craft, 1971;Kanarick, 1966;Laming, 1969) or when RT fluctuated intrasequentially according to trial by trial variations of event probability (DeKlerk & Oppe, 1970;Geller & Pitz, 1970). Moreover, when choice RTs) were classified according to both relative frequency and prediction outcome, RTs were faster following correct than incorrect predictions, and, within each prediction outcome category, RTs were faster to the more probable stimulus (Geller, Whitman, Wrenn, & Shipley, 1971;Geller, Whitman, & Farris, 1972;Hinrichs & Craft, 1971). Geller et al hypothesized that Ss were most prepared after predicting the more frequently occurring stimulus and consequently reacted fastest when correctly predicting the more probable stimulus and slowest when incorrectly predicting this stimulus.…”

Section: Virginia Polytechnic Institute and State University Blacksbmentioning

confidence: 99%

Confidence ill stimulus predictions and choice reaction time

Whitman

1973

Memory & Cognition

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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 S5 made predictions and the validity of E's confidence estimate was manipulated between Ss. When E's 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 E's judgments were random.