title: Within-trial contrast: The effect of probability of reinforcement in training.
abstract: There is evidence that pigeons prefer conditioned reinforcers that are preceded by greater effort over those that are preceded by less effort (an effect that has been attributed to within-trial contrast). In past research the probability of reinforcement for correct choice of the conditioned reinforcer has been 100%, however, the high level of reinforcement for both alternatives in training may result in a performance ceiling when choice between those alternatives is provided on test trials. In the present study we tested this hypothesis by including a group for which the probability of reinforcement in training was only 50%. Pigeons were trained on two simultaneous discriminations, one that was preceded by a 30 peck requirement the other by a single peck requirement. On test trials, we found a significant preference for the S+ that required the greater effort in training for pigeons trained with 100% and a small but nonsignificant effect for pigeons trained with 50% reinforcement. Although the hypothesis that the within-trial contrast effect was constrained by a performance ceiling was not confirmed, we did find a reliable within-trial contrast effect with 100% reinforcement.
authors.affiliation: University of Kentucky, Lexington, KY 40506, United States.
authors.forename: Cassandra D
authors.initials: CD
authors.lastname: Gipson
authors.forename: Holly C
authors.initials: HC
authors.lastname: Miller
authors.forename: Jérôme J D
authors.initials: JJ
authors.lastname: Alessandri
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Zentall
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D010856:Columbidae; D004193:Discrimination Learning / Q000502:physiology*; D011337:Probability Learning; D012055:Reinforcement Schedule; D012054:Reinforcement, Psychology