Discriminability of fixed-ratio schedules for pigeons: effects of absolute ratio size.

Cohen (1975) asked pigeons to tell two fixed-ratio schedules apart.

Birds pecked on two keys. One key needed 20 pecks for food. The other needed 22, 24, 30, 40, or 60 pecks.

The bird had to pick the key with the smaller ratio. Correct picks paid off. Sessions kept going until the bird chose the right key 9 times out of 10.

Pigeons could spot the smaller ratio even when the gap was only 10 percent.

Discrimination got sharper as the absolute numbers grew. A 20 vs 30 gap was easier than 20 vs 22.

The birds still picked the smaller ratio when the numbers were large, showing fine-tuned sensitivity to ratio size itself.

Sturmey et al. (1996) extends this work. They let pigeons choose between a steady FR 20 and a variable schedule that averaged 20 but sometimes asked for only 1 peck. Birds picked the variable side. The 1975 study shows pigeons notice ratio size; the 1996 study shows the smallest component, not the average, controls preference.

Fine et al. (2005) looks at interval instead of ratio. Pigeons showed only weak preference for fixed over random intervals. Together these papers say: pigeons read ratio size more clearly than interval randomness.

Singh et al. (1982) found birds accept bigger ratios after longer search times. Cohen (1975) adds that once the ratio starts, its exact size is a clear signal the bird can use.

Your client can feel the difference between a 5-response task and a 15-response task even if you never say the number out loud. Use larger, clearly separated ratios when you want the shift to stand out. Keep VR minimum at 1 if you want the learner to stay engaged. Ratio size itself is a cue—no extra tokens or praise needed.