Some discriminative properties of fixed ratio performance in the pigeon.
Pigeons can tell big ratio runs from small ones, but only when the difference is at least 30 responses.
01Research in Context
What this study did
Researchers worked with pigeons on fixed-ratio schedules. The birds had to peck 35, 40, 42, 58, 60, or 65 times to get food.
After finishing a ratio, the pigeon saw two keys. One key led to food if the bird had just finished a big ratio. The other key paid if the ratio had been small. The team tested how small the difference could get before the bird could no longer tell them apart.
What they found
Pigeons chose the correct key when the ratio difference was 30 pecks or more. They were right almost every time.
When the difference dropped to 20 pecks or less, accuracy fell apart. Adding a short delay between the ratio and the choice made the birds guess even more.
How this fits with other research
Findley et al. (1965) showed that breaking big ratios into chunks with conditioned reinforcement keeps chimpanzees working fast. Hoffman et al. (1966) now show that pigeons can use the feel of the just-finished ratio as its own cue. Together, the studies tell us that both added cues and built-in cues can guide ratio performance.
Blackman (1970) later used the same choice method with fixed-interval schedules and got strong stimulus control. The pattern holds across schedule types: animals treat their recent work history as a signal.
Thomson (1974) chained FI schedules and found pauses that matched the matching law. The current FR study adds that ratio size, not just time, can become a discriminative stimulus.
Why it matters
If you run large-ratio programs with learners, know that they can feel the difference between big and small ratios. When ratios are too close, add extra cues like tokens, lights, or brief breaks to sharpen the distinction. This keeps accuracy high and reduces guess-work.
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02At a glance
03Original abstract
The discriminative control over a spatial choice response exercised by prior behavior was studied using a procedure involving discrete exposures to a two-member chained schedule. The initial member (red key) was either a smaller or larger fixed ratio (Mix FR:FR), the completion of which produced, after a 1-sec delay, two white response keys. If the larger FR had been completed as the initial chain member, a single peck on the right white key was reinforced; after the smaller FR, a peck on the left white key was reinforced. Frequencies of unreinforced responses (S(Delta) responses) were determined with several pairs of red-key FRs: 95-5, 75-25, 65-35, 60-40, 58-42 and 50-50. The S(Delta) response frequencies were low through the FR pair 65-35; sharp increases were obtained with pairs 60-40 and 58-42. Later, curves analogous to stimulus generalization functions were obtained using a probe procedure. Finally, the delay interval between completion of a red-key FR and the white-key choice response was manipulated: results were variable, but S(Delta) response frequencies tended to increase with increasing delays.
Journal of the experimental analysis of behavior, 1966 · doi:10.1901/jeab.1966.9-1