Procrastination by pigeons with fixed-interval response requirements.
Delays cheapen work requirements the same way they cheapen food—track both when shaping self-control.
01Research in Context
What this study did
Fraley (1998) tested pigeons on an adjusting-delay schedule. Birds chose between two keys. One key gave a small food pile right away. The other key made the bird wait, then do more pecks to earn a bigger pile.
The wait time changed each session until the pigeon picked both keys equally. The researchers called this the indifference point. They ran the test with different fixed-interval lengths to see how wait time changed the value of work.
What they found
Pigeons acted as if delayed work lost value the same way delayed food does. Longer waits lowered the indifference point. The drop followed a hyperbolic curve, just like reinforcer delay curves.
In plain words, a 20-second wait made ten extra pecks feel like fifty. The birds only accepted the extra work if the delay stayed short.
How this fits with other research
Torres et al. (2011) later repeated the setup with rats and saw the same hyperbolic shape. They also found choice wobbles that fade after long training. Together, the two studies show the math works across species.
Eisenmajer et al. (1998) looked at the flip side: unsignaled delays to food delivery. They saw quick drops in preference, too. Both papers agree that any delay—whether before the work or before the payoff—hurts value.
Cullinan et al. (2001) moved from lab to classroom. Kids with ADHD learned to wait twenty-four hours for bigger rewards. The bird data give the numbers behind that teaching: you must keep the delay short at first, then stretch it.
Why it matters
When you write a self-control program, treat response effort like reinforcer size: both lose pull when delayed. Start with almost instant work requirements, then fade in short, predictable delays. Graph the learner's indifference points; if the curve is steep, slow the fade. This keeps motivation high while you build patience.
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02At a glance
03Original abstract
Two experiments studied the phenomenon of procrastination, in which pigeons chose a larger, more delayed response requirement over a smaller, more immediate response requirement. The response requirements were fixed-interval schedules that did not lead to an immediate food reinforcer, but that interrupted a 55-s period in which food was delivered at random times. The experiments used an adjusting-delay procedure in which the delay to the start of one fixed-interval requirement was varied over trials to estimate an indifference point--a delay at which the two alternatives were chosen about equally often. Experiment 1 found that as the delay to a shorter fixed-interval requirement was increased, the adjusting delay to a longer fixed-interval requirement also increased, and the rate of increase depended on the duration of the longer fixed-interval requirement. Experiment 2 found a strong preference for a fixed delay of 10 s to the start of a fixed-interval requirement compared to a mixed delay of either 0 or 20 s. The results help to distinguish among different equations that might describe the decreasing effectiveness of a response requirement with increasing delay, and they suggest that delayed reinforcers and delayed response requirements have symmetrical but opposite effects on choice.
Journal of the experimental analysis of behavior, 1998 · doi:10.1901/jeab.1998.69-185