TEMPORALLY SPACED RESPONDING BY PIGEONS: DEVELOPMENT AND EFFECTS OF DEPRIVATION AND EXTINCTION.
In the first five or six sessions on a DRL 20-sec schedule of reinforcement there developed a stable performance characterized by a relatively constant conditional probability of occurrence (IRTs/op) of interresponse times (IRTs) of durations greater than 5 or 6 sec. Extinction and the level of deprivation changed both the overall rate of responding and the form of the function relating the duration of an IRT to its value of IRTs/op. The value of IRTs/op decreased more rapidly for short than for longer IRTs, resulting in the emergence of a finer discrimination of IRT duration.