Quantification of the effects of chlorpromazine on performance under delayed matching to sample in pigeons.

Zigler et al. (1989) gave pigeons a memory game. The birds had to peck a key that matched a sample they saw seconds earlier.

The team injected chlorpromazine before some sessions. Doses ranged from 0.5 to 12.5 mg/kg. They watched how the drug changed accuracy and speed.

Chlorpromazine hurt memory in two ways. Birds forgot faster and mixed up the samples more often.

Yet the drug did not slow their pecking. The problem was memory, not motor skill.

WEINELong (1963) saw the same drug help pigeons. It restored food pecking that amphetamine had shut down. The tasks differ: simple fixed-ratio work versus memory. The drug hurts memory but can steady over-aroused birds.

Martens et al. (1989) gave diazepam to humans learning new button sequences. Like chlorpromazine, the drug harmed new learning more than old. Both papers show that calming drugs hit acquisition hardest.

Goldman et al. (1979) found the same pattern with stimulants in monkeys. Acquisition dropped while old chains stayed intact. Across species and drug classes, new learning is the fragile part.

If a client starts an antipsychotic, expect new skills to take longer. Break tasks into tiny steps and give extra practice trials. Keep the old routines running—they are safer from drug effects.