The response-reinforcement dependency in fixed-interval schedules of reinforcement.
On FI schedules, the post-reinforcement pause tracks the interval length, not whether a response is required to start it.
01Research in Context
What this study did
Glynn (1970) tested what sets the length of the pause after food on fixed-interval schedules.
Pigeons worked on FI 30-s, FI 120-s, and FI 300-s. Sometimes any peck after the interval paid off; sometimes the bird had to peck once to start the timer.
The key question: does forcing a start-up response change how long the bird waits after food?
What they found
Longer FI meant longer pauses. The 300-s schedule produced the biggest post-reinforcement breaks.
Whether a response was needed to begin the interval made no difference. Time alone controlled the pause.
How this fits with other research
Harzem et al. (1978) seems to disagree. They paid birds for ending long pauses and saw pauses shrink. Their result looks opposite until you notice they added a new rule: reinforcement now depended on pause length itself. The 1970 study held that rule constant.
Foster et al. (1979) extend the story. They showed blackout after wrong pecks shortens pauses, but only on long FI schedules. Again, an extra contingency—not just the FI value—was in play.
Neuringer et al. (1968) back Glynn (1970). They separated time from response count and found timing, not number of responses, drives latency. Both papers point to the clock, not the counter.
Why it matters
When you build FI schedules in the clinic, remember the pause is set by the interval you pick, not by added response requirements. If you see shorter pauses than expected, check for hidden contingencies—extra reinforcement for quick starts or blackout after errors—before you blame timing. Keep the rule clean and the pause will follow the clock.
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Join Free →Run your next FI 2-min session as usual, then try an FI 2-min with a single start-up peck required; graph pauses to confirm they stay the same.
02At a glance
03Original abstract
Pigeons were exposed to four different schedules of food reinforcement that arranged a fixed minimum time interval between reinforcements (60 sec or 300 sec). The first was a standard fixed-interval schedule. The second was a schedule in which food was presented automatically at the end of the fixed time interval as long as a response had occurred earlier. The third and fourth schedules were identical to the first two except that the first response after reinforcement changed the color on the key. When the schedule required a peck after the interval elapsed, the response pattern consisted of a pause after reinforcement followed by responding at a high rate until reinforcement. When a response was not required after the termination of the interval, the pattern consisted of a pause after reinforcement, followed by responses and then by a subsequent pause until reinforcement. Having the first response after reinforcement change the color on the key had little effect on performance. Post-reinforcement pause duration varied with the minimum interreinforcement interval but was unaffected by whether or not a response was required after the interval elapsed.
Journal of the experimental analysis of behavior, 1970 · doi:10.1901/jeab.1970.14-55