Pair comparison of durations.

Pigeons were trained on a pair comparison task where a red light of one duration was followed by a green light of a second duration. Following a duration pair two choice keys were lit and one choice was reinforced if the duration of red was longer than green, and the alternate choice was reinforced if green was longer than red. Duration pairs consisted of all possible combinations of the durations .5, 1, 2, and 4 sec in one condition, and 2, 4, 8, and 16 sec in a second condition. Generalization tests with novel duration pairs were given under both conditions. Under a final set of conditions, interstimulus intervals of 2, 5, 10, and 30 sec were interposed between the first (red) and second (green) durations. Pigeons responded appropriately in most cases, with accuracy a function of the relative temporal difference between the members of a duration pair. Accuracy on transfer problems was above 70% in most instances, but in some cases suggests factors apart from relative temporal differences influenced performance. Accuracy declined with increases in the interstimulus interval, but remained above chance levels even when the longest interstimulus interval was used.