Effects of d-amphetamine and chlordiazepoxide on spaced responding in pigeons.

Researchers gave pigeons a DRL 20-second schedule. The birds had to wait 20 seconds between pecks to earn food.

They then injected low or high doses of two drugs. One drug was a stimulant (d-amphetamine). The other was a calming drug (chlordiazepoxide).

The team watched how the drugs changed the birds' timing and any extra movements the birds made.

Small doses only hurt timing for half the birds. Big doses always made the birds peck too soon or stop pecking.

The birds did not use new side movements to help them wait. The drugs acted right on the timing system.

Byrd (1972) and Cicerone (1976) used the same DRL task but changed lights instead of drugs. They showed that timing is tightly tied to the stimulus in front of the bird. Hearst et al. (1970) now shows that drugs can break that timing without needing new cues.

Flory et al. (1974) tied the birds’ wings so they could not pace or turn while waiting. This raised response rates and cut rewards. The 1970 drug study found no helpful collateral moves, so both papers warn that blocking or drugging natural pacing can wreck DRL success.

Wilson et al. (1973) gave the same stimulant under mild punishment. There, amphetamine sometimes raised punished pecks. In the 1970 DRL case, the same drug only lowered or stopped spaced pecks. The difference is the contingency: punishment keeps the door open for rate increases, DRL does not.

If a client starts new meds, watch their DRL or self-control tasks closely. Even small dose changes can erase hard-won wait times. Have backup plans ready, like shorter DRL values or extra prompts, to keep the skill alive.