The dissociation of discriminative and conditioned reinforcing functions of stimuli with changes in deprivation.

Fischer et al. (1968) asked a simple question. If an animal is no longer hungry, what happens to the cues that used to guide and reward its behavior?

They trained pigeons to peck when colors told them food was coming. Then they pre-fed the birds until they were full. The team tracked two things: did the birds still notice the color signals, and did the color still work as a tiny reward on its own?

Right after the big meal, the color lost most of its reward power. The birds almost stopped working for it. Yet they still pecked when the color simply signaled upcoming food.

After many identical full-belly sessions, both kinds of control faded together. Early on, reward value drops faster than signal value. Later, the decline evens out.

Boutros et al. (2011) extends this split. They showed that one coin-sized reward immediately nudges the next choice, while a long run of coins builds lasting preference. The 1968 study is the mirror image: take the hunger away and the reward side cracks first.

Fisher et al. (2020) put the idea to work. They used a clear extinction cue, an S-delta, to guard against resurgence of problem behavior. Their cue kept its power even when reinforcers were gone, echoing the 1968 finding that discriminative control outlives conditioned reinforcement.

Castilla et al. (2013) and Thompson et al. (1971) line up on method. All four labs tweaked food deprivation inside schedule-controlled setups. The newer papers show adjunctive drinking rising or falling with hunger level, while K et al. show cue functions shifting. Together they map how motivation tunes different behavior streams.

For your next session, remember that satiation is a scalpel. If you want to dull a conditioned reinforcer (like token sounds), let the client eat first. If you need the signal power to stay, keep the hunger level steady or add extra practice. This lets you protect instructions while you thin rewards.