Effects of intertrial reinforcers on self-control choice.

The researchers set up a classic self-control game for pigeons. Birds could pick a small food reward right away or wait for a bigger reward later. During the wait time, the team slipped in extra bits of food on a variable schedule. They wanted to see if these free snacks would make the birds act more 'impulsive' and take the smaller, faster payoff.

The extra food came at different rates. Sometimes the birds got more free snacks, sometimes fewer. The scientists tracked how often each bird chose the quick, small reward versus the bigger, delayed one.

The free snacks worked like a charm. Birds chose the small, immediate reward more often when they got extra food during the wait. The effect grew stronger as the snack rate increased. The results fit the hyperbolic decay model - each extra snack made the delayed reward lose value faster.

In plain terms: more free food now equals less patience for the bigger payoff later.

This finding flips an earlier result on its head. Higgins et al. (1992) found that fewer trials (lower 'income') made rats more patient. Wulfert (1994) shows more free food during trials makes pigeons less patient. The difference? T's team reduced the total number of earning opportunities. E's team added extra, unearned rewards during waits. Both changes affect how organisms value delayed payoffs, but in opposite directions.

The study extends work by Clarke et al. (2003) and Carlin et al. (2012). Those teams taught humans with intellectual disabilities to wait for bigger rewards by giving them activities during delays. Wulfert (1994) shows that what you do during the wait matters - free food rewards increase impulsivity, while engaging activities can build patience.

The results support the hyperbolic decay model first tested by Sanford et al. (1980). That study showed how absolute delay changes preference. Wulfert (1994) adds that the density of rewards during those delays also shapes choice, consistent with the same mathematical model.

When you program delays in reinforcement schedules, watch what happens during the wait. Giving clients extra tokens, snacks, or attention while they wait for a bigger reinforcer might accidentally teach them to pick smaller, faster payoffs instead. If you want to build patience, keep the delay period lean. Save the bonus reinforcers for after the client chooses the larger, delayed option. This is especially important in token economies, DRO procedures, or any intervention where clients wait for better rewards.