Spaced responding in multiple DRL schedules.

ZIMMERMAELLIOTT et al. (1962) put rats on two DRL schedules in the same session. One schedule required a 36-second pause between responses. The other required an 18-second pause.

The rats earned food for waiting the right amount of time. The researchers then gave the rats amphetamine to see if the drug would mess up the timing.

The rats learned to tell the two schedules apart. They waited longer in the 36-second part and shorter in the 18-second part.

Amphetamine made the rats respond faster at first. The timing got worse. After a few drug days, the rats adjusted. Their timing came back even though the drug was still given.

Parsons et al. (1993) later gave us numbers. They used peak-deviation analysis to measure exact pause times. This builds on the 1962 finding by showing how to track tiny timing shifts.

Barber et al. (1977) saw a similar bounce-back. Rats on fixed-interval schedules also returned to baseline pause patterns after amphetamine. Both studies show tolerance develops.

NEVIN et al. (1963) tested amphetamine the very next year. They used an avoidance schedule instead of DRL. The drug still increased response rate, proving the effect is not schedule-specific.

If you use DRL to reduce rapid talking or hand flaps, know that stimulant medication may briefly speed the client up. Keep data for at least a week. The behavior should re-stabilize as tolerance grows. If it does not, the dose or timing may need a tweak.