[2] John Gibbon originally proposed SET to explain the temporally controlled behavior of non-human subjects.
[1] He initially used the model to account for a pattern of behavior seen in animals that are being reinforced at fixed-intervals, for example every 2 minutes.
[3] An animal that is well trained on such a fixed-interval schedule pauses after each reinforcement and then suddenly starts responding about two-thirds of the way through the new interval.
(See operant conditioning) The model explains how the animal's behavior is controlled by time in this manner.
A stimulus that signals the start of a timed interval closes a switch, allowing pulses to enter an accumulator.
[8] In 1993, John Wearden claimed that human behavior exhibits appropriate scalar properties, as was indicated by experiments on internal production with concurrent chronometric counting.