Patterns of responding within sessions.

Chandler et al. (1992) watched how fast lab animals pressed a lever during one session.

They kept the reinforcer timing the same but changed other schedule details.

The team drew smooth curves that showed speed rising, peaking, then falling again.

Every session looked like a little hill: responses climbed, topped out, then slid down.

Reinforcement rules decided where the hill peak sat and how steep the sides were.

The way the animal pressed mattered less than the way the treats were scheduled.

Rutland et al. (1996) later saw the same hill shape when two VI schedules ran together.

Their data say the peak moves if you add the reinforcer rates across both schedules.

Wanchisen et al. (1989) had already shown tiny spikes that line up with single reinforcers.

The 1992 paper widens that idea: the whole session, not just local moments, bends.

McLean et al. (1981) found early-session sensitivity drops in multiple schedules.

K’s hill curve gives one clean rule that covers all those smaller earlier bits.

If you graph a client’s responses minute-by-minute, expect a hill, not a flat line.

Shift reinforcer timing and you can slide the peak earlier or later to fight fatigue.

Use this to shorten warm-up time or to place the hardest trials on the uphill side.