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

Dómhnall J. Jennings*, Eduardo Alonso, Esther Mondragón, Mathijs Franssen, Charlotte Bonardi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)233-248
Number of pages16
JournalJournal of Experimental Psychology: Animal Behavior Processes
Issue number3
Publication statusPublished - 13 Aug 2013
Externally publishedYes


  • Conditioned responding
  • CR acquisition
  • Fixed and variable stimulus duration
  • Pavlovian conditioning

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Experimental and Cognitive Psychology


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