EFFECTS OF SECOND SIGNALS ON RESPONSE TIME TO FIRST SIGNALS UNDER CERTAINTY AND UNCERTAINTY

3 groups of 16 male undergraduates matched for response speed on a pretest, were subsequently tested for RT to a 1st signal S1 light under stimulus-response certainty and stimulus-response uncertainty. For Groups 1 and 2, an S2 light, requiring no response, followed S1 at interstimulus intervals (ISIs) of either 50, 100, or 150 msec., randomly selected, or not at all. For Group 1, 2 lights were in a reciprocal relation as S1 and S2; if 1 flashed on 1st, the other became the potential S2 light. For Group 2, the same 2 lights served as S1, but a 3rd light was used exclusively for S2. Group 3 was never exposed to an S2 light. Results showed no significant group differences under the certainty condition. Under uncertainty, RT for Group 1 was significantly longer than that for either Groups 2 or 3, but the latter 2 groups did not differ significantly. Effects were independent of ISI. Results were interpreted in terms of response-conflict views of double-stimulation effects. (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1969 American Psychological Association.