Choice, changeover, and travel.
Making it harder to switch between two options strengthens bias toward the richer one and cuts switching.
01Research in Context
What this study did
Pigeons pecked two keys for food. Each key paid off on its own variable-interval schedule.
To switch keys the bird had to walk down a short alley. The alley length changed across conditions.
Researchers counted how often birds changed keys and which key they preferred.
What they found
When the alley was long, birds switched less and favored the richer key even more.
The birds moved past simple matching toward overmatching — more bias than the payoff rates predicted.
Extra travel cost made the richer schedule look even better.
How this fits with other research
Shull et al. (1967) saw the same pattern by adding a delay instead of a walk. Both studies show that any switch cost pushes choice toward the richer side.
Szempruch et al. (1993) later tested adult humans with the same VI-VI setup. People showed mixed styles — some matched, some undermatched, some locked in. The tidy overmatching seen in pigeons did not always appear.
Pickering et al. (1985) also found overmatching under continuous-access VI schedules without travel. Together the papers say overmatching can emerge whenever staying on the richer side is easier than moving.
Why it matters
When you run concurrent schedule baselines, keep travel or transition effort low. A long walk, extra clicks, or a slow app screen can artificially inflate preference for the richer option. Check your setup: if switching is hard, your data may show overmatching that is procedure-driven, not learner-driven.
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Shorten the distance or clicks needed to move between two choice panels to keep effort from skewing preference.
02At a glance
03Original abstract
Since foraging in nature can be viewed as instrumental behavior, choice between sources of food, known as "patches," can be viewed as choice between instrumental response alternatives. Whereas the travel required to change alternatives deters changeover in nature, the changeover delay (COD) usually deters changeover in the laboratory. In this experiment, pigeons were exposed to laboratory choice situations, concurrent variable-interval schedules, that were standard except for the introduction of a travel requirement for changeover. As the travel requirement increased, rate of changeover decreased and preference for a favored alternative strengthened. When the travel requirement was small, the relations between choice and relative reinforcement revealed the usual tendencies toward matching and undermatching. When the travel requirement was large, strong overmatching occurred. These results, together with those from experiments in which changeover was deterred by punishment or a fixed-ratio requirement, deviate from the matching law, even when a correction is made for cost of changeover. If one accepted an argument that the COD is analogous to travel, the results suggest that the norm in choice relations would be overmatching. This overmatching, however, might only be the sign of an underlying strategy approximating optimization.
Journal of the experimental analysis of behavior, 1982 · doi:10.1901/jeab.1982.38-35