Relative reinforcer magnitude under a nonindependent concurrent schedule of cocaine reinforcement in rhesus monkeys.

Llewellyn et al. (1976) let rhesus monkeys choose between two levers. Both levers delivered cocaine, but one gave a bigger dose.

The schedule was concurrent and non-independent. This means either lever could pay off at any time, so the monkey had to keep track of which dose was larger.

The monkeys pressed the lever that gave the larger dose about twice as often. Their response split almost matched the dose split.

In plain words, the animals followed the matching law: more behavior went to the bigger reinforcer.

Meisch et al. (2016) repeated the setup with alcohol instead of cocaine and saw the same pattern. This direct replication shows the dose-size rule works across drugs.

Schwartz (1969) looked at pigeons working for food on fixed-ratio schedules and found no change in response rate when food amount changed. The birds still picked the side that gave more food per minute, but their running speed stayed flat. Species, drug type, and schedule structure explain why the two studies look different yet both support the matching idea.

Matson et al. (1999) tested noncontingent delivery and saw almost no magnitude effect. Because the reinforcers were free, the animals did not have to allocate responses, so the size cue mattered less. This contrast highlights that the matching law shows up strongest when the subject’s own behavior produces the payoff.

The study reminds us that reinforcer size, not just rate, drives choice. When you set up concurrent programs for clients, weigh both how often and how big each payoff is. If a preferred edible is larger or lasts longer, expect the client to shift toward that option even if both choices pay on the same schedule. Use this to fine-tune token piles, break lengths, or screen-time chunks so the intended behavior earns the richer deal.