Nonconsumption of the reinforcer under drug action.

Scientists gave cats milk they usually loved. Then they gave the cats methylphenidate, the same drug many kids take for ADHD. The cats stopped drinking the milk even though it sat right in front of them.

The team watched each cat alone in a cage. They measured how much milk the cat drank with and without the drug. No extra training or prompts were used.

The drug turned the milk into nothing. Cats that once lapped every drop now ignored it. The reinforcer lost its power.

This tells us methylphenidate can wipe out the value of food. Behavior that once earned milk may stop cold while the drug is active.

Dicesare et al. (2005) later saw the same drug flip the function of problem behavior. In their study, disruptive acts were kept alive by adult attention only when the participant was off methylphenidate. On the drug, attention no longer worked as a reinforcer. Together, the two papers show the drug can cancel different kinds of reinforcers across species.

Davison (1969) tested d-amphetamine, a close cousin, in monkeys. Small doses boosted key pressing for food, but higher doses shut it off. The pattern matches the cat study: stimulants first can brighten, then erase, reinforcer power as dose rises.

Bart et al. (2010) looked at kids with both ADHD and motor delays. Methylphenidate improved their movement scores. This seems opposite to the cat result, but the kids got clinical doses and earned praise, not food. The drug may spare social reinforcers while dulling edible ones.

If a client on methylphenidate suddenly stops working for edible rewards, do not assume the teaching plan is broken. The drug may have turned the food into cardboard. Try praise, toys, or brief activities instead. Re-run your functional assessment after any med change, just like Dicesare et al. (2005) did. A reinforcer that worked last month may be dead today.