Earning and obtaining reinforcers under concurrent interval scheduling.
Standard matching fails when one alternative takes more work to collect—add an earning ratio to save the prediction.
01Research in Context
What this study did
Pigeons pecked two keys. Each key paid off on its own variable-interval schedule.
The twist: one schedule required more pecks to collect the same food. The birds could earn food faster on one side but still pick it up on either side.
The team tracked two numbers: how often food was earned and how often it was actually grabbed. They wanted to see if the classic matching law still predicted choice when these numbers differed.
What they found
When earning rates were unequal, the birds no longer matched response ratios to food ratios. The old equation broke.
A new equation saved the day. It included both the earning ratio and the obtaining ratio. With both terms, the data lined up perfectly.
How this fits with other research
Macdonald et al. (1973) showed perfect matching when earning and obtaining were the same. Hall (2005) keeps their method but reveals the hidden assumption: equal effort to collect.
Ghaziuddin et al. (1996) saw stubborn under-matching in cows. The 2005 study hints that unequal earning costs might explain that stubbornness.
Catania et al. (1974) found matching with drug reinforcers. Hall (2005) extends the story by showing the equation must grow when collection effort varies.
Why it matters
If you run concurrent programs, check whether clients must work harder to collect from one side. When that happens, ditch the simple matching rule. Track both earning and obtaining, then adjust schedules so the effort to collect is equal. This keeps choice balanced and prevents one option from sliding into extinction.
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02At a glance
03Original abstract
Contingencies of reinforcement specify how reinforcers are earned and how they are obtained. Ratio contingencies specify the number of responses that earn a reinforcer, and the response satisfying the ratio requirement obtains the earned reinforcer. Simple interval schedules specify that a certain time earns a reinforcer, which is obtained by the first response after the interval. The earning of reinforcers has been overlooked, perhaps because simple schedules confound the rates of earning reinforcers with the rates of obtaining reinforcers. In concurrent variable-interval schedules, however, spending time at one alternative earns reinforcers not only at that alternative, but at the other alternative as well. Reinforcers earned for delivery at the other alternative are obtained after changing over. Thus the rates of earning reinforcers are not confounded with the rate of obtaining reinforcers, but the rates of earning reinforcers are the same at both alternatives, which masks their possibly differing effects on preference. Two experiments examined the separate effects of earning reinforcers and of obtaining reinforcers on preference by using concurrent interval schedules composed of two pairs of stay and switch schedules (MacDonall, 2000). In both experiments, the generalized matching law, which is based on rates of obtaining reinforcers, described responding only when rates of earning reinforcers were the same at each alternative. An equation that included both the ratio of the rates of obtaining reinforcers and the ratio of the rates of earning reinforcers described the results from all conditions from each experiment.
Journal of the experimental analysis of behavior, 2005 · doi:10.1901/jeab.2005.76-04