The influence of dl-, d-, and l-amphetamine and d-methamphetamine on a fixed-ratio schedule.

Hearst (1960) gave lab rats tiny shots of different amphetamine forms. The rats pressed a lever for food on a fixed-ratio 50 schedule—every 50 presses earned one pellet.

The team watched how each drug shape changed the steady press-rate. They tracked total responses, pauses, and overall pattern.

All amphetamine types sped up pressing, but each isomer tweaked the pattern in its own way. The abstract does not say which form worked most, only that changes were clear and dose-related.

Davison et al. (1989) later used the same FR baseline with pigeons and methadone. Methadone did the opposite—it slowed ratio responding and made birds switch to the interval side of a mixed schedule. Together the papers show FR rate can move up or down depending on drug class.

Capriotti et al. (2017) used FR schedules in kids, not for drugs but for tic suppression. Their fixed-amount DRO worked fine, proving FR contingencies stay useful across species and problems.

Dugan et al. (1995) kept the single-case design but moved from pharmacology to feeding. Both studies prove small, steady manipulations give clean, interpretable curves.

If a client’s FR data suddenly look faster, more variable, or show long pauses, check new meds first. Amphetamines can double response rate without you changing anything else. Re-baseline after any stimulant change and use the same FR size so you know behavior, not pharmacy, moved the numbers.