Habituation contributes to within-session changes in free wheel running.

Simpson et al. (2001) watched rats run in a wheel for one hour. They tracked how running speed changed minute-by-minute inside each session. Three small experiments tested whether the drop-off came from tiredness or from habituation.

They gave some rats a short break, changed the wheel room, or re-exposed them to the wheel after time away. Each test was designed to separate fatigue from simple getting-used-to-it.

Running always started fast and then slowed within the same hour. When the rats got a quick pause or a new room, their speed bounced back. That rebound points to habituation, not muscle fatigue.

The wheel itself became less interesting, not the rats' muscles more tired. The authors saw the classic habituation signs: spontaneous recovery, dishabituation, and stimulus specificity.

PREMACSALZINGER et al. (1962) and PREMACK et al. (1963) already showed that restricted wheel access shortens the gaps between bursts of running. Simpson et al. (2001) use the same burst-tracking method but add a new why: habituation explains the drop, not exhaustion.

Silverman et al. (1994) and Buitelaar et al. (1999) found that food-reinforced lever presses also drift down within a session. They blamed reinforcement rate. Simpson et al. (2001) show a similar drift when the reinforcer is wheel running itself, offering habituation as the engine.

Rutland et al. (1996) saw within-session flattening in pigeons under autoshaping. The rat wheel data now mirror that pattern, suggesting habituation can hide reinforcement effects across species and responses.

If a client's responding fades mid-session, try a brief break, a new seat, or a different room before you blame fatigue or up the reinforcer size. Quick environmental novelty can dishabituate the task and bring responding back without extra calories or tokens. Treat the slump as boredom, not exhaustion.