title: Unraveling sources of stimulus control in a temporal discrimination task.
abstract: In temporal discriminations tasks, more than one stimulus may function as a time marker. We studied two of them in a matching-to-sample task, the sample keylight and the houselight that signaled the intertrial interval (ITI). One group of pigeons learned a symmetrical matching-to-sample task with two samples (2 s or 18 s of a center keylight) and two comparisons (red and green side keys), whereas another group of pigeons learned an asymmetrical matching-to-sample task with three samples (2 s, 6 s, and 18 s) and two comparisons (red and green). In the asymmetrical task, 6-s and 18-s samples shared the same comparison. In a subsequent retention test, both groups showed a preference for the comparison associated with the longer samples, a result consistent with the hypothesis that pigeons based their choices on the duration elapsed since the offset of the houselight (i.e., sample duration + retention interval). Results from two no-sample tests further corroborated the importance of the ITI illumination as a time marker: When the ITI was illuminated, the proportion of choices correlated positively with the retention interval; when the ITI was darkened, choices fell to random levels. However, the absolute value of choice proportions suggested that the sample stimulus was also a time marker. How multiple stimuli acquire control over behavior and how they combine remains to be worked out.
authors.affiliation: School of Psychology, University of Minho, Campus de Gualtar, 4710, Braga, Portugal. carlos.arop@gmail.com.
authors.forename: Carlos
authors.identifier: 0000-0002-4435-6880
authors.initials: C
authors.lastname: Pinto
authors.affiliation: School of Psychology, University of Minho, Campus de Gualtar, 4710, Braga, Portugal.
authors.forename: Armando
authors.initials: A
authors.lastname: Machado
mesh_terms: D000818:Animals; D002755:Choice Behavior; D010856:Columbidae; D004193:Discrimination Learning; D010775:Photic Stimulation
keywords: Coding; Delayed matching-to-sample; Many-to-one matching; Pigeon; Stimulus control; Timing