Michael J. Beran, Ph.D.
Curriculum Vitae

Journal Articles
Sites of Interest

Contact Me:  [email protected]

Last updated: 
September 1, 2021



Beran, M. J., & Evans, T. A. (2006). Maintenance of delay of gratification by four chimpanzees (Pan troglodytes): The effects of delayed reward visibility, experimenter presence, and extended delay intervals. Behavioural Processes, 73, 315-324.

Previous research in our laboratory has demonstrated that chimpanzees can delay gratification by inhibiting consumption of available food items for as long as 3 minutes as an experimenter transfers additional food items from a transparent container to a bowl placed in front of the subject. In this study, we examined the influence of the visibility of the food source, as well as the presence of the experimenter, on 4 chimpanzeesí self-control in this paradigm. In Experiment 1 an experimenter transferred 15 preferred food items between a distant opaque container and a bowl placed in front of the subject. In Experiment 2 we tested the chimpanzees with an automated system that (in the absence of the experimenter) transferred up to 36 highly preferred food items from a universal food dispenser to a container located either inside or outside of the subjectís enclosure. There were no differences in self-directed behaviors or attentiveness to the food items between the self-imposed and externally imposed delay conditions. A final experiment with the automated paradigm indicated that individuals could delay gratification for up to 11 minutes in order to obtain all 36 food items.

Return to Top