Shull, R. L. (2005).
The sensitivity of response rate to the rate of variable-interval reinforcement
for pigeons and rats: A review.
Journal of the Experimental Analysis of Behavior, 84, 99-
110.
The relation between the rate of a response (B) and the rate of its
reinforcement (R) is well known to be approximately hyperbolic: B = kR/(R + Ro),
where k represents the maximum response rate, and Ro indicates the rate of
reinforcers that will engender a response rate equal to half its maximum value.
A review of data reported in 17 published papers revealed that, under variable-
interval schedules of reinforcement, Ro was usually lower when pigeons were the
subjects than when rats were the subjects. The value of k, in contrast, did not
differ consistently between pigeons and rats. Some accounts interpret Ro as the
rate of alternative, unscheduled reinforcers in the situation, expressed in
units of the scheduled reinforcer. So interpreted, the difference in Ro implies
that less alternative reinforcement (relative to the scheduled reinforcement)
typically is available to pigeons in their operant conditioning chambers than it
is to rats in theirs. Whether or not that interpretation of Ro is valid, the
pigeon--rat difference in Ro ensures that for reinforcer rates above about 10
per hour, response rate will be noticeably less sensitive to changes in
reinforcer rate (and presumably to changes in other incentive and motivational
operations) with pigeons than with rats as subjects, at least with the
experimental conditions typically employed.
Key words: Herrnstein’s hyperbola, variable-interval schedule, reinforcer
effectiveness, response strength, pigeons, rats