Parker D M, Leydel R, Delius J, Williams M, 2002, "A critical duration effect in suprathreshold pattern discrimination" Perception 31 ECVP Abstract Supplement
A critical duration effect in suprathreshold pattern discrimination
D M Parker, R Leydel, J Delius, M Williams
The existence of critical duration effects in the integration of stimulus energy at threshold has been known since 1885 following Bloch's observations. Evidence is presented that a critical duration effect also occurs in a suprathreshold-pattern-discrimination task. Twelve observers performed a speeded, successive, 480 trial, same/different discrimination task. One of six randomly selected patterns was shown on a monitor screen for 500 ms and after a blank interval of 1200 ms was followed by a second pattern, either randomly the same or different, which was displayed for a variable duration between 20 and 1000 ms. Decision times showed a significant effect of exposure duration (F7,77 = 2.65, p = 0.02), with minima occurring at 80 ms and 120 ms. Error rates were low (5%) and did not show an effect of pattern duration. In a second experiment, simple RTs to the same set of patterns at the same exposure durations were examined and a small but non-significant rise over the exposure durations from 20 ms to 120 ms was found (F7,77 = 1.74, p = 0.11). It is concluded that decision times for successive same/different discriminations are fastest with exposure durations in the region of 80 - 120 ms.
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