Matching and contrast on several concurrent treadle-press schedules.

Six pigeons pecked two treadles for grain.

Each treadle paid off on its own variable-interval schedule.

The researcher switched the payoff rates every few sessions.

He tracked how fast the birds switched sides and how hard they worked.

The birds’ response rates almost perfectly matched the grain rates.

When the left treadle paid twice as often, the birds pecked it twice as much.

After a switch, the new favorite side surged and the old side dipped.

This two-part pattern is called matching plus contrast.

McKearney (1970) saw the same matching, but payoff came after short blackouts.

The birds still matched, proving the law holds even with brief pauses.

Ginsburg et al. (1971) showed that longer extinction before reinforcement makes contrast bigger.

K’s treadle data fit that rule: bigger payoff shifts created bigger contrast spikes.

Van Houten et al. (1980) later asked if contrast changes how the bird pecks.

It doesn’t: response duration stayed the same even while rate swung up or down.

Together the four studies draw a clear line: matching sets the ratio, contrast adds the swing, and the form of the response stays untouched.

Keep your reinforcement ratios steady if you want steady client effort.

When you must change ratios, expect a brief burst or drop in behavior.

Plan for this swing and don’t read the burst as new learning—it’s just contrast fading.