The effect upon simple animal behavior of different frequencies of reinforcement, Part II: separate control of the reinforcement of different IRTs.
Reinforcement rate for specific pause lengths quickly re-shapes the whole response pattern.
01Research in Context
What this study did
Kelly (1973) worked with rats pressing a lever on a VI schedule. He set up separate circuits so only certain inter-response times (IRTs) earned food. One circuit paid off short pauses, another paid long pauses, and so on.
By flipping a switch the experimenter could change which IRT class was reinforced. He then counted how the whole pause-length distribution shifted.
What they found
When short pauses were paid, rats made more short pauses. When long pauses were paid, long pauses grew. The entire IRT histogram slid to match the reinforced zone.
The switch happened fast—within one session the animals chased the money. Schedule design, not the animal’s habit, drove the shape of responding.
How this fits with other research
Anonymous (1995) later showed the same rule in rat foraging: nose-poke rate tracked reinforcement rate the way IRTs did here. The principle crosses response forms.
Udhnani et al. (2025) moved from rats to humans. College students picked rules that had previously delivered richer reinforcement, proving the rate rule travels all the way to rule-governed choice.
Newman et al. (2021) applied the idea to problem behavior. They used noncontingent reinforcement—just flooding the room with edibles—to cut escape-maintained behavior. No extinction, no shaping; they only changed how often reinforcement occurred, echoing the 1973 finding that rate alone can reshape behavior.
Why it matters
Your client’s response pattern is not fixed; it’s a mirror of what the schedule pays for. If you want shorter pauses during DTT, reinforce the trials that follow brief waits. If you want slower, careful work, reinforce longer IRTs. Before adding punishment or extinction, try re-allocating your reinforcement dollars to the IRT zone you actually want to grow.
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02At a glance
03Original abstract
Rats' responding was stabilized for over 35 days on 4-min variable-interval reinforcement. Reinforcements per hour for 4-sec wide classes of interresponse times were then separately controlled by adjusting those for each class to the variable-interval values that had just prevailed. This produced little or no change in interresponse times, indicating that the new procedure was substantially equivalent to a variable-interval schedule. The variable-interval schedule produced a high and stable conditional probability of interresponse times in the 0- to 4-sec class, associated with a peak in reinforcements per hour for this class. Reducing the reinforcements per hour for this class while raising that for another class (by 3.3 reinforcements per hour) significantly reduced the conditional probability of 0- to 4-sec interresponse times. Restoring the 3.3 reinforcements per hour to the 0- to 4-sec class significantly elevated the conditional probability of interresponse times in this class. Hence, it is concluded that the distribution of interresponse times produced by a subject during some variable-interval schedules is determined partly by the relative reinforcement of different interresponse times that the variable-interval schedule provided.Reprinted from Part II of the Final Report of Research under Contract DA-49-007-MD-408 with the Medical Research and Development Board, Office of the Surgeon General, Department of the Army, 31 December 1954. Edwin B. Newman, Responsible Investigator; Douglas Anger, Research Assistant and author of report. Experimental work done in the Psychological Laboratories of Harvard University.
Journal of the experimental analysis of behavior, 1973 · doi:10.1901/jeab.1973.20-301