The substitutability of reinforcers.
Reinforcers interact like economic goods—map substitute, complement, or independent links before you plan choice interventions.
01Research in Context
What this study did
Green et al. (1993) wrote a theory paper. They asked, 'What happens when two reinforcers can swap for each other?'
They pulled data from human and animal labs. Then they built math rules that show when reinforcers act like substitutes, complements, or neutral items.
What they found
The team showed that reinforcers do more than sit on a preference list. They interact like grocery goods: Coke can replace Pepsi, but cookies and milk go together.
If you ignore these links, the matching law gives wrong forecasts. Add a 'substitutability' dial and the forecasts sharpen.
How this fits with other research
Hamm et al. (1978) had already seen the pattern. They paid kids to do low-interest tasks and watched the kids slide toward other available activities. Leonard's paper gives that slide a name: selective substitution.
Atnip (1977) claimed reinforcement is relational—rates matter, not raw size. Leonard keeps the relational idea but adds the new knob of interaction type.
Cohen et al. (1993) ran a lab study the same year. They found that a single reinforcer momentarily pulls choice but does not shift long-term preference. Leonard's model says the long view still rules, yet the momentary pull can look different if the reinforcers are substitutes versus complements.
Why it matters
Next time you run a choice program, test if the backup rewards trade places with the target reward. If they do, treat them as substitutes and expect faster shifts. If they team up, treat them as complements and use both. Write 'sub, com, ind' on your data sheet and watch the interaction, not just the rank.
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Join Free →During your next reinforcer assessment, present pairs and note if picking one cuts, boosts, or leaves untouched the later picking of the other—mark the interaction type.
02At a glance
03Original abstract
Substitutability is a construct borrowed from microeconomics that describes a continuum of possible interactions among the reinforcers in a given situation. Highly substitutable reinforcers, which occupy one end of the continuum, are readily traded for each other due to their functional similarity. Complementary reinforcers, at the other end of the continuum, tend to be consumed jointly in fairly rigid proportion, and therefore cannot be traded for one another except to achieve that proportion. At the center of the continuum are reinforcers that are independent with respect to each other; consumption of one has no influence on consumption of another. Psychological research and analyses in terms of substitutability employ standard operant conditioning paradigms in which humans and nonhumans choose between alternative reinforcers. The range of reinforcer interactions found in these studies is more readily accommodated and predicted when behavior-analytic models of choice consider issues of substitutability. New insights are gained into such areas as eating and drinking, electrical brain stimulation, temporal separation of choice alternatives, behavior therapy, drug use, and addictions. Moreover, the generalized matching law (Baum, 1974) gains greater explanatory power and comprehensiveness when measures of substitutability are included.
Journal of the experimental analysis of behavior, 1993 · doi:10.1901/jeab.1993.60-141