Discrimination of duration ratios by pigeons (Columba livia) and humans (Homo sapiens).

Humans (Homo sapiens) were trained on 2 versions of a 2-alternative, forced-choice procedure. First, subjects judged which of 2 successive stimulus durations was longer. Second, subjects judged whether the ratio of the 2 durations was less or greater than a criterion ratio (e.g., 2:1). Accuracy was significantly lower for the task in which the judgment was made according to the ratio of the 2 durations. This result is different than that obtained by Fetterman, Dreyfus, and Stubbs (1989), who trained pigeons (Columbia livia) on a similar pair of tasks and found that pigeons' performance was comparable for the 2 discriminations. Comparisons of the pigeon and human data suggest that humans were more accurate than pigeons when the judgment involved which duration was longer, but that accuracy was comparable for the ratio-based task.