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The effect of stimulus distribution form on the acquisition and rate of conditioned responding: Implications for theory

Jennings, D�mhnall J.; Alonso, Eduardo; Mondrag�n, Esther; Franssen, Mathijs; Bonardi, Charlotte


D�mhnall J. Jennings

Eduardo Alonso

Esther Mondrag�n

Mathijs Franssen


In four experiments rats were conditioned to an auditory conditioned stimulus (conditioned stimulus; CS) that was paired with food, and learning about the CS was compared across two conditions in which the mean duration of the CS was equated. In one, the CS was of a single, fixed duration on every trial, and in the other the CS duration was drawn from an exponential distribution, and hence changed from trial to trial. Higher rates of conditioned responding to the fixed than to the variable stimulus were observed, in both between- (Experiment 1) and within-subject designs (Experiments 2 and 3). Moreover, this difference was maintained when stimuli trained with fixed or variable durations were tested under identical conditions (i.e., with equal numbers of fixed and variable duration trials)—suggesting that the difference could not be attributed to performance effects (Experiment 3). In order to estimate the speed of acquisition of conditioned responding, the scaled cumulative distribution of a Weibull function was fitted to the trial-by-trial response rates for each rat. In the within-subject experiments specific differences in the pattern of acquisition to fixed and variable CS were shown; a somewhat different pattern was found when intertrial interval (ITI) was manipulated (Experiment 4). The implications of these findings for theories of conditioning and timing are discussed.

Journal Article Type Article
Acceptance Date Feb 4, 2013
Publication Date 2013
Deposit Date Dec 10, 2018
Journal Journal of Experimental Psychology: Animal Behavior Processes
Print ISSN 0097-7403
Electronic ISSN 0097-7403
Publisher American Psychological Association
Peer Reviewed Peer Reviewed
Volume 39
Issue 3
Pages 233-248
Public URL