Performance on variable-interval schedules arranged singly and concurrently.
Pigeons under-match on concurrent VI schedules, but a simple power tweak fixes Herrnstein’s equation.
01Research in Context
What this study did
Pigeons pecked two keys on variable-interval schedules. The keys ran alone first, then together.
Researchers logged every peck and second spent on each key. They wanted to see if birds matched their effort to the payoff rates.
What they found
Birds under-matched. They did not peck or stay in exact proportion to the grain delivered.
A power-function tweak to Herrnstein’s equation fit the data better than the original straight line.
How this fits with other research
Smith et al. (1975) saw the same under-matching the year before, so the result is solid.
Pickering et al. (1985) later kept the session open all day and saw over-matching instead. Long sessions flip the pattern.
Renne et al. (1976) ran the same concurrent VI setup with adult humans the same year. People matched almost perfectly, showing the equation works better for humans than pigeons.
Why it matters
When you set up concurrent reinforcement, expect clients to under-match if the reinforcers are small or sessions are brief. Track both responses and time; they can differ. If you need stricter matching, lengthen the session or add cues that make the payoff ratios clearer.
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02At a glance
03Original abstract
Extensive parametric data were obtained from pigeons responding on variable-interval schedules arranged on three, two, and one response keys. Number of responses on the keys, the time spent responding on the keys, and the number of reinforcements obtained on the keys were measured. Response rates on each key were an increasing function of the reinforcement rate on that key, and an inverse function of the reinforcement rate on the other keys. In terms of preference, both response and time-allocation ratios undermatched ratios of obtained reinforcements, and the degree of undermatching was consistent both within, and between, two- and three-schedule data. When absolute response-rate data were analyzed according to Herrnstein's (1970) quantitative account, obtained values of assumed constants were not consistent either within or between conditions. However, a power-function modification of Herrnstein's account fitted the data well and provided similar exponent values to those obtained for the undermatching of preference ratios.
Journal of the experimental analysis of behavior, 1976 · doi:10.1901/jeab.1976.25-335