Compound stimulus control by discriminative stimuli associated with high and moderate response rates.

Researchers trained rats to press a lever at two different speeds. One stimulus told the rat to press fast on a fixed-ratio schedule. Another stimulus told the rat to press slower on a variable-interval schedule.

Then they turned on both stimuli at the same time. They wanted to see which speed the rat would choose.

When the tone and light came on together, the rats pressed at a medium speed. Their rate landed halfway between the fast FR rate and the slower VI rate.

The compound cue did not create a new, wild rate. It averaged the two trained rates.

Two years earlier the same lab showed the opposite effect. Hendry et al. (1969) found that if a noise already signaled "no food," adding a light did not give the light any power. The old stimulus blocked the new one.

The 1971 study flips that result. Here, both cues already control strong but different rates. When combined, the rates blend instead of one blocking the other.

Davison et al. (1991) later showed that horses, like rats, follow basic stimulus-control rules. The averaging effect seen here likely spans species.

When you mix cues that signal different response speeds, clients may settle in the middle. If you pair a "work fast" card with a "slow and steady" card, don't expect either extreme. Expect an average pace. Plan reinforcement and criteria around that blended rate.