Two temporal parameters of free operant discriminated avoidance in the rhesus monkey.

The team worked with rhesus monkeys in a small lab cage. Each monkey could press a lever at any time.

A tone came on every so often. If the monkey pressed during the tone, the tone turned off and no shock happened. If it did not press, a brief shock arrived.

The researchers changed two things: how long the safe, quiet period lasted and how long the warning tone lasted. They watched how fast the monkeys pressed the lever.

When the safe period got longer, the monkeys slowed down. Most presses happened only when the tone was on.

Changing the tone length hardly mattered. Shock rate stayed the same no matter what.

In short, a longer break between chances made the monkeys wait instead of work.

Garcia et al. (1971) ran a near-copy of this setup and saw the same drop in pressing when the safe gap grew. The two monkey studies line up like bricks.

Dukhayyil et al. (1973) switched to pigeons pecking a key with no tone at all. Longer response-shock gaps still cut rate, showing the rule holds across birds and monkeys.

Kelly (1973) kept the lever-press task but swapped the knob from time to shock strength. Doubling either intensity or duration pushed rate up the same amount, proving the lever stays still unless the aversive stakes change.

If you run avoidance programs for severe problem behavior, keep the safe period short. A long "no-work" window will drop the client’s active coping responses. Try 5–10 s safe spans and watch response effort stay high.