The effects of schedule history and the opportunity for adjunctive responding on behavior during a fixed-interval schedule of reinforcement.
Old schedules and small side behaviors can erase the fixed-interval scallop.
01Research in Context
What this study did
Researchers worked with rats on a fixed-interval 60-second schedule.
First they gave each rat a different history: long pauses, fast pressing, or no special training.
Then they let half the rats drink water during the session while the others stayed dry.
They counted lever presses to see how history and water changed the usual FI scallop.
What they found
Rats trained to pause pressed slowly and steady—no scallop.
Rats trained to press fast kept the high rate—also no scallop.
Water mattered only for the pause group: it made them press even less.
The normal FI curve vanished when history or water pulled the other way.
How this fits with other research
Okouchi et al. (2006) later showed the same thing in pigeons: just remembering a slow schedule can flatten the curve.
Rogers-Warren et al. (1976) proved that extra reinforcers also wipe out the scallop; M et al. add water as another curve-killer.
Johnson et al. (1994) zoomed in on when the water appears; together the papers say both timing and history set the final pattern.
Why it matters
Your client’s past schedules are baggage they carry into every new program.
If a kid learned to wait 30 s for tokens, he may stay slow even on a new FI 10 s.
Check for side behaviors—sipping water, doodling, scrolling—that could pull effort away from the target response.
Start sessions with a probe: run a few FI cycles and watch the curve; if it’s flat, reshape history first, then move on.
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Join Free →Run a one-minute FI probe; if the curve is flat, insert a brief pause-training or speed-training phase before the main program.
02At a glance
03Original abstract
The effects of schedule history and the availability of an adjunctive response (polydipsia) on fixed-interval schedule performance were investigated. Two rats first pressed levers under a schedule of food reinforcement with an interresponse time greater than 11 s, and 2 others responded under a fixed-ratio 40 schedule. All 4 were then exposed to a fixed-interval 15-s schedule. Water was continuously available under these conditions, but after responding became stable on the fixed-interval schedule, access was experimentally manipulated. With water freely available, subjects did not display characteristic fixed-interval response rates and patterns (i.e., scalloping or break-and-run). Instead, they exhibited predictable, stable patterns of behavior as a function of their schedule histories: Subjects with the interresponse-time history exhibited low response rates, and those with the fixed-ratio history exhibited high rates. Manipulating the amount of water available resulted in marked changes in response rates for rats with the interresponse-time history but not for those with the fixed-ratio history. The results illustrate the multiple causation of behavior by its previous and current schedules of reinforcement and other concurrent factors.
Journal of the experimental analysis of behavior, 1991 · doi:10.1901/jeab.1991.55-313