Trade-offs in stimulus control in a temporal discrimination task

The datasets generated and analysed inthe study are available in the DataRepositoriUM repository: https://doi.org/10.34622/datarepositorium/F9SWHO
To study how multiple stimuli may control discriminative behavior, we exposed fifteen pigeons to a symbolic matching-to-sample task with three samples that differed only in duration (2, 6, and 18s) and two keylight colors as comparisons. The pigeons learned to choose one comparison after the shortest sample, and the other comparison after the intermediate and longest samples. A 30-s intertrial interval (ITI), illuminated with the houselight, separated the trials. Previous data has suggested that, in this arrangement, both sample keylight and the ITI houselight influence choice. To assess this joint stimulus control, we introduced two tests. In the no-sample test, the keylight was not illuminated and the comparisons followed the ITI immediately; in the dark-ITI test, the houselight was not illuminated. Results confirmed that both stimuli influenced choice, with an apparent trade-off between them: The more a pigeon relied on one stimulus, the less it seemed to rely on the other. We discuss potential models of joint stimulus in temporal discrimination tasks.
This study was conducted at the Psychology Research Center (PSI/01662), School of Psychology, University of Minho, supported by the Foundation for Science and Technology (FCT) through the Portuguese State Budget (Ref.: UIDB/PSI/01662/2020). Armando Machado is a member of the William James Center for Research supported by the Portuguese Foundation for Science and Technology (UID/04810/2020), and of the Brazilian National Institute of Science and Technology on Behavior, Cognition, and Teaching supported by INCT-ECCE / CNPq Grant #465686/2014–1, FAPESP Grant#2014/50909–8, and CAPES Grant#8887.136407/2017–00).