Effect of training delays and start and stop markers on the choose-short effect in pigeons.

Pigeons were trained in a matching-to-duration task using short and long filled intervals. Group 2/8 was trained with 2- and 8-s intervals, Group 4/10 with 4- and 10-s intervals, and group marker with 2- and 8-s intervals presented between 1-s start and stop markers. Extended-delay testing showed no significant choose-short effect (CSE) in any group. It was hypothesized that the lack of a CSE may have resulted from use of a variable delay (range 1-3s) during training. The same subjects were employed in Experiment 2 and were trained with a new set of comparisons and one of the alternate types of samples employed in Experiment 1. All training trials involved a 0-s delay. Extended-delay testing revealed a significant CSE in Groups 2/8 and 4/10 but only a weak, and statistically nonsignificant, CSE in group marker. It was concluded that use of a variable delay during training reduced the CSE. The notion that subjective shortening underlies the CSE provided an adequate account of these findings.