Fixed-ratio discrimination: effects of response-produced blackouts.

Lydersen et al. (1974) taught pigeons to tell two fixed-ratio schedules apart.

Birds pecked on one key for FR 20 and another key for FR 40.

A short blackout followed the last peck. The team then made the blackout longer so the time from first to last peck was the same on both ratios.

When timing was equal, the birds could no longer pick the correct key.

Choice accuracy fell apart even though the response count stayed different.

Control had moved from “how many pecks” to “how long the burst lasted.”

Dunham (1972) saw that delaying food lengthened the pause after reinforcement. That paper kept the ratio size the same and played with delay; the target paper kept time the same and played with ratio size. Together they show both timing and number matter, just in different places.

DARDANO et al. (1964) punished early, middle, or late responses in an FR. Punishing late responses broke the end of the chain. The 1974 blackout work lines up: the end of the ratio carries the stimulus control.

Crossman et al. (1985) found that small FRs can flip the usual pause pattern. Their small-ratio timing data support the idea that temporal cues inside the ratio, not the count itself, guide the animal.

If you are shaping a new skill, watch the time the learner spends in the response burst, not just the number of responses. You might pick the wrong prompt or criterion if you only count. Try adding a brief pause or extra stimulus at the end of the ratio to sharpen stimulus control.