A quantitative analysis of extreme choice.
Extreme reinforcer ratios push choice toward indifference—plan for weaker preference than the matching law predicts.
01Research in Context
What this study did
Davison et al. (1995) tested pigeons on two keys. One key paid off up to 27 times more often.
The birds chose which key to peck. The team watched how extreme ratios changed preference.
What they found
When the payoff gap hit 27:1, the birds acted almost indifferent. They still picked the richer side, but far less than the matching law says they should.
A contingency-discriminability model fit the data better than classic matching.
How this fits with other research
Glenn (1988) saw a similar bend in rats. Under dependent VR schedules, animals slid toward exclusivity when only the active counter advanced.
Henson et al. (1979) kept pigeons on plain concurrent VI schedules and found tight matching. The new study shows that pushing ratios past 20:1 snaps that line.
Bromley et al. (1998) later moved the test to humans with ID and preschoolers. They used easier FR schedules and still saw reinforcement-controlled choice, proving the rule holds across species and tasks.
Why it matters
If you run very lean schedules, expect clients to act like the pigeons: they may not "see" the big payoff difference. Check for indifference before you blame motivation. Thin schedules still work, but you may need extra signals or denser flashes to keep the contingency clear.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →Plot your current reinforcer ratio; if it tops 20:1, add salient cues or tighten the lean side to keep the contingency visible.
02At a glance
03Original abstract
Six homing pigeons were trained on a variety of concurrent variable-interval schedules in a switching-key procedure. Unlike previous work, reinforcer ratios of up to 160 to 1 and concurrent extinction variable-interval schedules were arranged in order to investigate choice when reinforcer-frequency outcomes were extremely different. The data obtained over 11 conditions were initially analyzed according to the generalized matching law, which fitted the data well. The generalized matching law was then fitted only to conditions in which the reinforcer ratios were between 1 to 10 and 10 to 1. The deviations of choice measures from the other four more extreme reinforcer-ratio conditions were significantly more towards equal choice than predicted by this second generalized matching fit. A contingency-discriminability model, which predicts such deviations, described the data more effectively than did the generalized matching law, and also correctly predicted the maintenance of responding on both alternatives when one was associated with extinction.
Journal of the experimental analysis of behavior, 1995 · doi:10.1901/jeab.1995.64-147