Choice for periodic schedules of reinforcement.
Fixed terminal links can make leaner schedules look better as entry work grows.
01Research in Context
What this study did
Researchers put pigeons in a two-key setup. Each key led to a final link. One final link gave food every 10 responses. The other gave food every 30 seconds.
They then made the birds peck more and more before they could reach these final links. They watched which key the birds picked as the work got harder.
What they found
As the entry work grew, the birds flipped their choice. They started to pick the leaner 30-second schedule more often.
This broke the usual rule. Earlier work said birds should match the richer schedule. Here, the leaner one won out.
How this fits with other research
HERRNSTEISLOANE (1964) had shown birds love variable schedules. That study used aperiodic final links and found clear preference for the richer option.
Clark et al. (1970) used fixed, periodic final links. The birds no longer followed the matching rule. The two studies seem to clash, but the key is schedule type.
Iwata et al. (1990) later showed toddlers also follow ratio rules. The bird data still guide us, yet we must note when schedules are fixed versus variable.
Why it matters
When you set up choice programs, check if the back-end schedules are fixed or variable. If they are fixed, leaner options may gain appeal as front-end work rises. Test this in your next concurrent schedule probe.
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Run a quick probe: keep the same two back-end schedules but raise the token cost to reach them. Watch if the learner flips preference.
02At a glance
03Original abstract
Pigeons' responses in the presence of two concurrently available (initial-link) stimuli produced one of two different (terminal-link) stimuli according to identical but independent variable-interval schedules. Responding in the mutually exclusive terminal links was reinforced with food according to fixed-ratio schedules for six pigeons and according to fixed-interval schedules for two pigeons. None of the pigeons matched the proportion of (choice) responses in the initial links to the proportion of the rates of reinforcement obtained during the terminal links. Instead, as the values of each of the terminal-link schedules were increased by a constant amount, the choice proportions for the stimulus associated with the smaller of the two values increased, even though the relative rates of reinforcement during the terminal links decreased. These results are incompatible with those from previous studies with aperiodic (variable-interval or variable-ratio) schedules. The present results do suggest, however, that in transforming aperiodic schedules into their periodic equivalents, it may be necessary to consider the size of the smallest interreinforcement interval comprising the terminal-link schedules.
Journal of the experimental analysis of behavior, 1970 · doi:10.1901/jeab.1970.14-73