Effects of delays on human performance on a temporal discrimination procedure: Evidence of a choose-short effect

Studies of temporal discrimination in non-human subjects have reliably shown a choose-short effect: higher matching accuracy on short-duration-sample trials than on long-duration-sample trials. This effect occurs as a function of increasing the delay between the onset of sample and comparison stimuli in a delayed matching-to-sample procedure. The present experiment investigated whether the choose-short effect could be demonstrated in human subjects under conditions which paralleled those used with non-human subjects. Subjects responded under a discrete-trial procedure in which they were required to push one of two buttons depending on the duration of a sample stimulus (a blue square on a computer monitor). Delays (0, 8, 16, and 32 s) separated sample and comparison stimuli (two white boxes) and were tested both within and across several sessions. Intermediate durations (probe stimuli between 2 and 4 s) were also presented. The addition of a delay between the sample and comparison stimuli produced a bias to judge intervals as short when the 8 and 32-s delays were tested across sessions and when the 0, 16, and 32-s delays were tested within the same session. Thus, the choose-short effect was produced in human subjects using the interval bisection procedure regardless of delay length.