Bisection of temporal intervals.

Eight rats were trained to make one response if a signal was shorter than a criterion duration and a different response if the signal was longer than the criterion. When exposed to intermediate durations, the rats bisected the interval at the geometric mean and the difference limen divided by the geometric mean was a constant. The rats learned new temporal discriminations more easily when the response maintained its relative, rather than its absolute, meaning. These data were interpreted in terms of a model of an internal clock that included a clock, a criterion, and a response rule.