The effect of increased response requirements on discriminative performance of the domestic hen in a visual acuity task.
FR 5–10 is the sweet spot for sharp discrimination; higher ratios add work without benefit.
01Research in Context
What this study did
The researchers trained hens to peck the brighter of two lights. Each correct choice earned food.
They slowly raised the work rule. Birds had to peck 1, 5, 10, 20, or 40 times before choosing.
What they found
Accuracy jumped when the ratio moved from 1 to 5–10 pecks. More work made the birds sharper.
Past FR 10, accuracy flat-lined and bias grew. Extra effort no longer helped.
How this fits with other research
Winton (1975) also saw sharper discrimination in pigeons, but proved peak shift still happens no matter how you present the stimuli. Together, the two studies say: you can tune accuracy with ratio size, yet stimulus control quirks remain.
English et al. (1995) showed that past VR history raises later FI response rates in rats. That paper and this one both warn: earlier or current ratio requirements echo through future performance.
Richardson (1973) found pigeon paired-associate learning follows an all-or-none rule. The hen data line up: once the ratio hits the sweet spot, learning looks sudden, not gradual.
Why it matters
When you shape a new discrimination, start with easy FR 1, then climb only to FR 5–10. Stop there. Going higher wastes time and can tilt responding toward one choice. The same rule works for kids, pigeons, or rats: find the least work that gives the clearest signal.
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Join Free →Track current FR on each discrimination task; if above 10, drop to 10 and watch accuracy stay the same with fewer errors.
02At a glance
03Original abstract
Six domestic hens were trained in a spatial discrimination task. A controlled reinforcement procedure insured that the ratio of scheduled and obtained reinforcement remained equal. Gray stimuli and gratings ranging in spatial frequency from 1 to 10 cycles per millimeter were presented in seven descending series of probes. The response requirement to the sample key was varied from fixed ratio 1 to fixed ratio 40 in seven experimental conditions. An increase in response requirements from fixed ratio 1 to fixed ratio 5 and fixed ratio 10 resulted in significantly higher accuracy at discriminable grating values. Further increases in response requirements did not consistently improve performance. Generally, response biases increased and occasionally became extreme for probes at finer gratings with increased response requirements.
Journal of the experimental analysis of behavior, 1993 · doi:10.1901/jeab.1993.60-595