title: Some properties of an adjusting-magnitude schedule of reinforcement: Implications for models of choice.
abstract: Rats were trained under a discrete-trials adjusting-magnitude schedule in which a response on lever A delivered either a larger or a smaller reinforcer (qA1and qA2) with equal probability, while a response on B delivered a reinforcer whose size qBwas adjusted according to the rats' choices. When A was preferred in a given block of trials, qBwas increased in the following block; when B was preferred, qBwas reduced in the following block. The oscillating changes in qB, analysed by the Fourier transform, could be described by a power spectrum with a dominant period of about 50 trial blocks. With qA1held constant, the equilibrium value of qB(qB(50)) was monotonically related to qA2, and exceeded the arithmetic mean of qA1and qA2when qA1was substantially greater than qA2. A model derived from the multiplicative model of intertemporal choice provided a post hoc description of the data. Simulation of block-by-block changes in qBderived from the model were generally consistent with the experimental data. Implications of the results for models of risky choice and for future use of the schedule in neurobehavioural experiments are discussed.
authors.affiliation: Division of Psychiatry, University of Nottingham, UK. Electronic address: c.m.bradshaw@hotmail.co.uk.
authors.forename: C M
authors.initials: CM
authors.lastname: Bradshaw
mesh_terms: D000818:Animals; D002755:Choice Behavior / Q000502:physiology*; D008297:Male; D008960:Models, Psychological; D011336:Probability; D051381:Rats; D012055:Reinforcement Schedule; D012054:Reinforcement, Psychology
keywords: Adjusting-magnitude schedule; Choice; Fourier transform; Multiplicative hyperbolic model; Reinforcer size; Risk sensitivity