A new tool that may measure certain absolute temporal properties of information processing in intact organisms is suggested by. investigations of temporal summation in single nerve cells. Two findings have led to this suggestion: One, the form of the temporal summation function (relating the intensity and duration required to evoke a criterion neural signal) depends on the analysis used by the investigator. Corresponding form variations occur in behavioral studies when the observer's task is varied. Two, the critical durations of fixed neural signals depend on the latency of the feature of the signal chosen as criterion; early features yield short critical durations and vice versa. The critical duration also varies in behavioral studies if one varies the observer's task, keeping the stimulus ensemble fixed.

These data lead to two inferences: One, the form of a behavioral temporal-summation function expresses the kind of hidden mental analysis mediating that behavior. Two, a behavioral critical duration is an indicator of the absolute timing of the hidden mental analysis mediating that behavior.