Consumption and response output as a function of unit price: manipulation of cost and benefit components.

Delmendo et al. (2009) asked kids to press a button for candy. They changed how many presses each candy cost. Sometimes the cost went up by more presses. Sometimes the candy got smaller. The total price stayed the same.

Kids worked alone at a computer. The screen showed two colored squares. Pressing the square earned the candy shown above it. The team counted how many candies kids ate in 10 minutes.

When the price went up, kids ate fewer candies. If two choices cost the same total price, kids picked about the same amount of each. It did not matter if the price rose because of more presses or smaller candy.

The children acted like smart shoppers. They looked at the whole deal, not just the work or the reward alone.

Galuska et al. (2006) saw the same price rule in monkeys getting drug shots. The monkeys still chased big shots even when the price was high. Only very high prices slowed them down. The kids stopped sooner, showing the rule holds across species but drugs push harder.

Webb et al. (1999) tested food-refusing preschoolers with a two-choice snack game. They kept the work the same and only changed how good the reward was. Kids ate more when the bite came with better toys. Xeres shows the flip side: keep the reward good and raise the work, intake drops.

Killeen (1978) first mapped how daily limits change eating. Xeres adds the next layer by splitting price into work and reward size. The old rule still works, but now we know which knob to turn.

You can use unit price to guard against satiation or escape. If a child starts to refuse tokens, check the price. Drop the number of responses or raise the payoff instead of jumping to new reinforcers. A quick price cut can bring the work back up without a full re-assessment.