Multiple fixed-interval schedules: transient contrast and temporal inhibition.
Contrast effects show up in FI schedules: pauses shorten after a run of short intervals and lengthen after a run of long intervals.
01Research in Context
What this study did
Pigeons pecked for food on two fixed-interval schedules that alternated.
One schedule was short (30 s), the other long (120 s).
The birds stayed on each schedule for 1, 3, 7, or 14 cycles before the switch.
The team measured how long the birds paused after each food delivery.
What they found
Early in a short-interval run, pauses were extra short.
Across a long-interval run, pauses grew even longer.
The pattern flipped when the schedule changed.
These swings are called transient contrast and temporal inhibition.
How this fits with other research
Born et al. (1974) ran a near-copy study. They also saw temporal inhibition, but proved it is driven by the rate of reinforcement, not by earlier response speed.
Dougan (1987) extended the idea. He showed that the length of the last interval still nudges the bird’s timing in the next interval.
Green et al. (1975) used variable-interval instead of fixed-interval schedules. They still found local contrast, showing the effect holds across schedule types.
Why it matters
Your learner’s pause after reinforcement is not fixed. It can shrink or stretch depending on what came before. If you run several quick DTT trials followed by a few long ones, expect faster starts after the quick set and slower starts after the long set. Track these swings so you do not mistake a pause change for a skill deficit.
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02At a glance
03Original abstract
Pigeons were exposed to four cycles per session of a multiple schedule in which each cycle involved twelve 60-sec fixed intervals followed by four 180-sec intervals [(12 FI 60-sec)(4 FI 180-sec) schedule]. Post-reinforcement pauses were shorter during the first few short intervals of each cycle than during later short intervals, and increased over the four long intervals of each cycle (positive and negative transient contrast). A (12 FI 15-sec)(4 FI 45-sec) schedule showed similar results. These two schedules differed in some other respects indicating effects of absolute FI duration on stimulus control. Differences in contrast properties between both these procedures and multiple variable-interval schedules were related to the pause-producing property of reinforcement on FI (temporal inhibition). Behavior under two other multiple fixed-interval schedules-(2 FI 360-sec)(1 FI 720-sec) and (3 FI 360-sec)(1 FI 720-sec)-differed in certain respects from both the (12 FI x-sec)(4 FI 3x-sec) schedules. These differences may be related to differences in the number of successive fixed intervals within a component (run length).
Journal of the experimental analysis of behavior, 1969 · doi:10.1901/jeab.1969.12-583