title: Effect of reinforcer magnitude on performance maintained by progressive-ratio schedules.
abstract: This experiment examined the relationship between reinforcer magnitude and quantitative measures of performance on progressive-ratio schedules. Fifteen rats were trained under a progressive-ratio schedule in seven phases of the experiment in which the volume of a 0.6-M sucrose solution reinforcer was varied within the range 6-300 microl. Overall response rates in successive ratios conformed to a bitonic equation derived from Killeen's (1994) Mathematical Principles of Reinforcement. The "specific activation" parameter, a, which is presumed to reflect the incentive value of the reinforcer, was a monotonically increasing function of reinforcer volume; the "response time" parameter, delta, which defines the minimum response time, increased as a function of reinforcer volume; the "currency" parameter, beta, which is presumed to reflect the coupling of responses to the reinforcer, declined as a function of volume. Running response rate (response rate calculated after exclusion of the postreinforcement pause) decayed monotonically as a function of ratio size; the index of curvature of this function increased as a function of reinforcer volume. Postreinforcement pause increased as a function of ratio size. Estimates of a derived from overall response rates and postreinforcement pauses showed a modest positive correlation across conditions and between animals. Implications of the results for the quantification of reinforcer value and for the use of progressive-ratio schedules in behavioral neuroscience are discussed.
authors.affiliation: University of Nottingham, Nottingham, UK.
authors.forename: J F
authors.initials: JF
authors.lastname: Rickard
authors.forename: S
authors.initials: S
authors.lastname: Body
authors.forename: Z
authors.initials: Z
authors.lastname: Zhang
authors.forename: C M
authors.initials: CM
authors.lastname: Bradshaw
authors.forename: E
authors.initials: E
authors.lastname: Szabadi
mesh_terms: D000818:Animals; D003216:Conditioning, Operant; D005260:Female; D051381:Rats; D017208:Rats, Wistar; D012055:Reinforcement Schedule; D012054:Reinforcement, Psychology