Discrete-trial choice in pigeons: Effects of reinforcer magnitude.
Animals often pick an uncertain large reward over a certain smaller one, and the size gap needed to tip the scale grows in a straight line.
01Research in Context
What this study did
The team used pigeons in a lab. Each trial gave two keys.
Peck left: always get three pellets. Peck right: maybe get ten pellets or maybe get none.
They changed the sure-thing amount across days to see when birds would switch.
What they found
Birds stayed on the risky key even when the sure side gave more than three pellets.
As the sure amount grew, preference moved toward it in a straight line.
The birds did not try to get the most food per minute; they liked the chance of the big hit.
How this fits with other research
Cicerone (1976) saw the same thing with mixed delays. Birds picked uncertain timing over fixed timing. McCann (1981) shows the pattern also holds for pellet size.
Choi et al. (2012) swapped pellets for tokens. Pigeons still chased the variable option, but only while the tokens stayed visible. This adds a cue-control twist the 1981 paper did not test.
Fine et al. (2005) looked at fixed versus random wait times and found only weak preference. That seems to clash with McCann (1981), but the 2005 study made the variable side worse on average. When the gamble is truly better, preference is strong; when it is worse, preference fades.
Why it matters
Your clients may also chase the “big win” even when a smaller sure payoff is worth more.
Use preference assessments that show both amount and probability.
If you want steady responding, deliver small sure reinforcers. If you want high engagement and can add signals, mix in an occasional large prize and pair it with a salient cue.
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02At a glance
03Original abstract
The preference of pigeons for large reinforcers which occasionally followed a response versus small reinforcers which invariably followed a response was studied in a discrete-trial situation. Two differently colored keys were associated with the two reinforcement alternatives, and preference was measured as the proportion of choice trials on which the key associated with uncertain reinforcement was pecked. A combination of choice and guidance trials insured that received distributions of reinforcement equalled the scheduled distributions. For five of six subjects, preference for the uncertain reinforcer appeared to be a linear function of the magnitude of the certain reinforcer. In addition, there was greater preference for the response alternative associated with uncertain reinforcement than would be expected on the basis of net reinforcer value.
Journal of the experimental analysis of behavior, 1981 · doi:10.1901/jeab.1981.35-23