Probability Effects on Stimulus Evaluation and Response Processes

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target word probability information, motor response preparation & word discrimination RT, college students

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Investigated the effects of probability information on response preparation and stimulus evaluation. Eight Ss responded with 1 hand to the target letter H and with the other to the target letter S. The target letter was surrounded by noise letters that were either the same as or different from the target letter. In 2 conditions, the targets were preceded by a warning stimulus unrelated to the target letter. In 2 other conditions, a warning letter predicted that the same letter or the opposite letter would appear as the imperative stimulus with .80 probability. Correct reactions times (RTs) were faster and error rates were lower when imperative stimuli confirmed the predictions of the warning stimulus. Probability information affected (1) the preparation of motor responses during the foreperiod, (2) the development of expectancies for a particular target letter, and (3) a process sensitive to the identities of letter stimuli but not to their locations.

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Citation / Publisher Attribution

Journal of Experimental Psychology: Human Perception and Performance, v. 18, issue 1, p. 198-216