Pigeons' choices in situations of diminishing returns: fixed- versus progressive-ratio schedules.
Clients track total payoff, not just the next token—drop rising response costs or give resets before they quit.
01Research in Context
What this study did
Researchers let pigeons peck two keys. One key always needed the same number of pecks. The other key needed more pecks every time it paid off.
They could reset the rising count by switching back to the steady key. The team watched which key the birds picked and when they switched.
What they found
The birds switched to the steady key sooner when a reset let the rising count drop back down. Without the reset they stayed longer on the climbing key.
The pigeons acted as if they tracked the total food per minute, not just the next piece. They left the climbing work when the overall payoff fell below the steady key.
How this fits with other research
HERRNSTEISLOANE (1964) saw pigeons pick variable interval over fixed interval. Attwood et al. (1988) now show the same animals also watch the long-run rate when the work rises, not just when timing varies.
Barnes et al. (1990) later shortened the session and shrank the food. Birds then jumped faster to the richer key. Together the three papers say: pigeons balance immediate effort against future payoff, and that balance moves if time or food size changes.
Iwata et al. (1990) tested toddlers on random-ratio versus random-interval keys. The kids, like the pigeons, pecked faster on ratio. The bird rule—more work per minute, more responses—holds across species.
Why it matters
When you shape a token board or DRH program, think beyond the next reinforcer. If the response cost keeps climbing, the client may quit even while rewards still come. Build in reset breaks or keep the ratio low enough that the overall payoff stays attractive. Watch for early escape as your signal the molar rate has dropped.
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02At a glance
03Original abstract
In two different discrete-trial procedures, pigeons were faced with choices between fixed-ratio and progressive-ratio schedules. The latter schedules entail diminishing returns, a feature analogous to foraging situations in the wild. In the first condition (no reset), subjects chose between a progressive-ratio schedule that increased in increments of 20 throughout a session and a fixed-ratio schedule that was constant across blocks of sessions. The size of the fixed ratio was varied parametrically through an ascending and then a descending series. In the reset condition, the same fixed-ratio values were used, but each selection (and completion) of the fixed ratio reset the progressive-ratio schedule back to its minimal value. In the no-reset procedure, the pigeons tended to cease selecting the progressive ratio when it equaled or slightly exceeded the fixed-ratio value, whereas in reset, they chose the fixed ratio well in advance of that equality point. These results indicate sensitivity to molar as well as to molecular reinforcement rates, and those molar relationships are similar to predictions based on the marginal value theorem of optimal foraging theory (e.g., Charnov, 1976). However, although previous results with monkeys (Hineline & Sodetz, 1987) appeared to minimize responses per reinforcement, the present results corresponded more closely to predictions based on sums-of-reciprocals of distance from point of choice to each of the next four reinforcers. Results obtained by Hodos and Trumbule (1967) with chimpanzees in a similar procedure were intermediate between these two relationships. Variability of choices, as well as median choice points, differed between the reset and no-reset conditions.(ABSTRACT TRUNCATED AT 250 WORDS)
Journal of the experimental analysis of behavior, 1988 · doi:10.1901/jeab.1988.50-375