Behavioral economics and within-session changes in responding.

Buitelaar et al. (1999) watched how lever pressing changed minute-by-minute inside one session. They used fixed-ratio schedules that paid off at high, medium, or low rates.

Each rat worked for food in a single long session. The team tracked both response count and demand curves as the minutes passed.

Responding slid downhill as the session aged. The drop was steeper and less symmetrical when the schedule paid faster.

Demand metrics moved with the slide, showing the animals' willingness to work faded faster under richer reinforcement.

Silverman et al. (1994) saw the same downhill pattern five years earlier. They pinned the cause on high reinforcement rate, not just time. The 1999 paper keeps that story but adds demand curves to measure the fade.

Gilroy et al. (2021) took the demand idea and used it in preference assessments. They showed elasticity can tell you which 'high-preference' items will really keep kids working. The lab work in Buitelaar et al. (1999) gives that clinic tool its backbone.

Rutland et al. (1996) looked at within-session drift under Pavlovian autoshaping. They also found flatter, later peaks when food came slowly. The two studies seem opposite: one says fast pay hurts later responding, the other says slow pay flattens it. The gap is in the measure: K tracked total lever presses, F tracked response timing. Both agree that reinforcement rate sculpts the within-session curve.

If you run long sessions, the client's motivation may sink just because time has passed, not because your procedure failed. Keep experimental or teaching sessions short when you need steady high rates. If you must go long, check demand with brief probe trials and be ready to swap in fresh reinforcers or a break.