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Effects of sucrose concentration on choice in an adjusting-magnitude schedule

•Rats were trained under a discrete-trials adjusting-magnitude schedule.•The indifference magnitude was determined for a range of sucrose concentrations.•Oscillation of the adjusting magnitude was analysed by the Fourier transform.•Indifference magnitude was inversely related to sucrose concentratio...

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Bibliographic Details
Published in:Behavioural processes 2018-12, Vol.157, p.562-569
Main Author: Bradshaw, C.M.
Format: Article
Language:English
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Summary:•Rats were trained under a discrete-trials adjusting-magnitude schedule.•The indifference magnitude was determined for a range of sucrose concentrations.•Oscillation of the adjusting magnitude was analysed by the Fourier transform.•Indifference magnitude was inversely related to sucrose concentration.•The findings have implications for models of ‘risky choice. Rats were trained under a discrete-trials adjusting-magnitude schedule in which a response on lever A delivered either a larger or a smaller sucrose reinforcer (qA1 = 8 μl, qA2 = 64 μl) with equal probability, while a response on B delivered a reinforcer whose size qB was adjusted according to the rats’ choices. When A was preferred in a given block of trials, qB was increased in the following block; when B was preferred, qB was reduced in the following block. The oscillating changes in qB, analysed by the Fourier transform, could be described by a power spectrum whose dominant frequency corresponded to a period of 40–50 trial blocks. The equilibrium value of qB (qB(50)) was inversely related to sucrose concentration; it significantly exceeded the arithmetic mean of qA1 and qA2 when the concentration was 0.2 or 0.4 M, but not when it was 0.8 or 1.6 M. Analysis by mixed-effects modelling revealed a trend for the power of oscillation of qB to increase monotonically with sucrose concentration; the period of oscillation was not systematically related to sucrose concentration. These results are consistent with predictions derived from a revised version of the multiplicative hyperbolic model of intertemporal choice.
ISSN:0376-6357
1872-8308
DOI:10.1016/j.beproc.2018.04.017