The effect of small sequential changes in fixed-ratio size upon the post-reinforcement pause.

The team worked with three pigeons in a lab chamber. They slowly raised the fixed-ratio requirement from 10 pecks to 160 pecks.

After each food delivery they measured how long the bird waited before pecking again. They tracked every pause across many sessions.

Pauses grew longer as the ratio grew bigger. The jump from 10 to 20 pecks added a little time. The jump from 80 to 160 pecks added a lot.

Pause length also became more variable at the higher ratios. One bird might wait 5 seconds, the next might wait 25 seconds.

Reid et al. (1987) later showed the same pause-size link holds across fixed, variable, and random ratios. They added that fixed ratios always produce the longest pauses.

Cohen (1975) used the same ratio range and found pigeons can tell the sizes apart. Better discrimination at higher ratios may explain why pauses stretch and become more variable.

Sheldon (1971) chained several fixed ratios together. The pause still grew with size inside each link, showing the rule works even in token-style schedules.

When you thin a reinforcement schedule, expect longer and less predictable wait times. Build this into your session length and prompt timing. If a learner stalls after big task sets, break the ratio into smaller chunks or add brief holds to keep the pause manageable.