Drugs and punished responding. I. Rate-dependent effects under multiple schedules.

McMillan (1973) tested how different drugs change punished lever pressing in rats. The rats worked under multiple schedules where some lever presses produced food and others also produced mild electric shock. Researchers gave amphetamine, chlorpromazine, and chlordiazepoxide to see how each drug altered punished versus unpunished responding.

The team recorded response rates before and after each drug dose. They looked at whether low-rate or high-rate segments changed more after medication.

Drug effects depended on how fast the rat was pressing before the injection. Low punished rates often increased more than low unpunished rates. High punished rates sometimes dropped while high unpunished rates stayed the same. Each drug showed its own pattern of rate-dependent changes.

Amphetamine boosted slow punished pressing the most. Chlorpromazine and chlordiazepoxide showed different rate shifts. The same drug could increase suppressed behavior in one rat while decreasing it in another, based on their baseline speeds.

Wilson et al. (1973) ran an immediate follow-up using only amphetamine. They confirmed that mild shock or intermittent punishment lets amphetamine raise low punished rates. This direct replication strengthens the rate-dependency claim.

Lucki et al. (1983) extended the idea beyond punishment. They proved that control response rate alone—not reinforcement frequency—determines whether amphetamine increases or decreases behavior. Their clean design shows the 1973 punished-rate effect is part of a broader rate-dependency principle.

Billings et al. (1985) added stimulus control as a buffer. Strong discriminative stimuli protected lever pressing from amphetamine disruption, even when reinforcement rates stayed equal. This means rate-dependency still operates, but sharp stimuli can soften the drug punch.

If you work with clients on psychotropic medications, remember that the same dose can lift or sink behavior depending on the child’s baseline rate. A slow self-injurious bite might increase after stimulants, while rapid stereotypy could fall. Always measure pre-drug response rates and watch for rate-dependent shifts during med changes. Pair clear discriminative stimuli with desired responses to help buffer any drug side effects.