Interval reinforcement of choice behavior in discrete trials.

Researchers placed pigeons in a box with two keys. Each key paid off on its own variable-interval schedule.

The birds chose in short, separate trials. After each payoff, the next trial began right away.

The pigeons' pecks matched the payoff rates. If the left key paid 70% of the time, about 70% of pecks hit that key.

Right after a payoff, the bird was less likely to switch keys on the next trial.

Macdonald et al. (1973) ran the same VI-VI setup and saw the same matching. Their test looked across whole sessions, while Nevin (1969) looked inside each short trial.

Bell (1999) used the same discrete-trial method but added time tracking. Choice still followed the matching law, yet the bird's last response time also mattered.

Hall (2005) later showed that if the two keys differ in how hard it is to earn food, plain matching breaks. You need to count both earning and getting rates.

The matching law is not just a lab curiosity. In the classroom, if one task pays off attention every 30s and another every 90s, the child will drift toward the richer schedule. Watch your own timing. If you want more work on the low-pay task, raise its payoff rate or add extra praise right after the child tries it. Track a few sessions to see if time spent on each task starts to match your payoff rates.