Effects of pentobarbital on fixed-ratio reinforcement.

Scientists gave pigeons a fixed-ratio 30 schedule. The birds had to peck a key 30 times to earn food.

Then they injected different doses of pentobarbital, a barbiturate. They watched how the drug changed pecking speed.

Low and medium doses made the birds peck faster. High doses slowed them down.

Each bird had its own sweet-spot dose. The curve looked like an upside-down U.

WALLER et al. (1962) saw the same drug boost pecking, but only after a time-out signal had stopped it. The 1963 paper shows the drug can also raise normal, unsuppressed rates.

Garcia (1974) later added d-amphetamine and found the drug effect flipped when baseline rates were slow. That study extends the 1963 curve by showing rate matters.

Baer et al. (1984) switched to rhesus monkeys that gave themselves pentobarbital. They still saw the same inverted-U, proving the shape holds across species and ways of giving the drug.

The inverted-U is a classic warning for BCBAs who consult on medical cases. A small dose may raise behavior, but more is not better. When you see sudden rate drops, ask the team if barbiturate dose just went up. Use this curve when you teach caregivers why precise dosing matters.