Inelastic supply: An economic approach to simple interval schedules.

The team cut the number of food pellets pigeons could earn. They kept the work rule the same: every 30 pecks still paid one pellet.

They ran three small tests. Each test made the pellet supply smaller. They watched how many pecks the birds gave for each pellet.

When pellets got scarce, the birds pecked more for each one. Their "cost" per pellet rose, just like price rises when gas is short.

Simple "more food, more work" rules could not explain this. The birds worked hardest when food was most scarce.

Gilroy et al. (2021) turned the same idea into a quick assessment. They let clients pick items, then raised the work price. Items that stayed high-rate are "inelastic" reinforcers you can bank on.

Iwata et al. (1990) seem to disagree. They saw response rates fall when reinforcement dropped in an "open" economy. The key difference: their animals could get free food after sessions. Dougan (1992) used a closed economy—no outside food—so scarcity really bit.

Iwata (1993) added the next brick. They gave free food on varying schedules and saw key pecks rise as free food shrank. Together the papers map an economic continuum: less free or paid reinforcement, more operant work.

Your client’s session is a tiny economy. If reinforcers feel endless, the child may coast. If top items are scarce, the same child may work harder per item.

Try tightening the supply of the best item while keeping the work demand steady. Watch the response rate; if it climbs, you’ve spotted an inelastic reinforcer you can lean on during tough teaching tasks.