Time-allocation, matching, and contrast.
Even with only one response option, behavior shifts in exact step with payoff changes, so watch for contrast when you thin reinforcement.
01Research in Context
What this study did
Shimp et al. (1974) worked with pigeons that pecked a single key.
The team changed how often pecks paid off.
They watched how the birds shifted their time and responses.
What they found
When the payoff rate dropped, the birds pecked less and spent less time at the key.
The shift matched the new payoff ratio, even with only one key.
This contrast effect showed matching law works without two choices.
How this fits with other research
Stubbs et al. (1970) had already shown that matching comes from local bursts right after a changeover delay.
Shimp et al. (1974) used no delay and still got matching, proving the rule is bigger than the burst trick.
Shimp et al. (1971) found matching in short multiple-schedule parts.
The 1974 study adds contrast inside one part, tightening the same thread.
Kunz et al. (1982) later showed whole peck sequences can match, stretching the idea from single responses to chains.
Why it matters
If you run a DRL or thin schedule, expect contrast: behavior drops more than the reinforcement cut alone predicts.
Watch for this when you fade token rates or stretch wait times.
A quick probe session after a rate change will tell you if the client’s response level is matching the new payoff, helping you decide whether to hold the line or adjust.
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Join Free →After any rate cut, count responses for five minutes—if they drop more than the cut, you’re seeing contrast and may need a slower step-down.
02At a glance
03Original abstract
A variable-interval schedule arranged food reinforcement for key pecking by pigeons on a single operandum at two rates, corresponding to two classes of reinforced interresponse times ranging from 1.5 to 2.5 sec and from 3.5 to 4.5 sec. The scheduled reinforcement rate for the higher component response rate was constant and equivalent to that of a variable-interval 4-min schedule. The scheduled reinforcement rate for the lower component response rate varied from zero to over 100 per hour. The number of occurrences of the constant component response rate varied inversely with the reinforcement rate for the variable component. This result, by definition a concurrent reinforcement interaction, or contrast, was the combined effect of two time-allocation functions, which together determine mean response rate: the time allocated to both component rates as a function of the total reinforcement rate, and the time allocated to a particular component rate as a function of the percentage of reinforcements for that component. The present experiment reveals a further parallel between the controlling relations for free responding on a single operandum and those for choice between two operanda; in each case, a concurrent reinforcement interaction can be found that corresponds to matching.
Journal of the experimental analysis of behavior, 1974 · doi:10.1901/jeab.1974.22-1