Foraging in a variable environment presents a classic problem of decision making with incomplete information. Animals must track the changing environment, remember the best options and make choices accordingly. While several experimental studies have explored the idea that sampling behavior reflects the amount of environmental change, we take the next logical step in asking how change influences memory. We explore the hypothesis that memory length should be tied to the ecological relevance and the value of the information learned, and that environmental change is a key determinant of the value of memory. We use a dynamic programming model to confirm our predictions and then test memory length in a factorial experiment. In our experimental situation we manipulate rates of change in a simple foraging task for blue jays over a 36. h period. After jays experienced an experimentally determined change regime, we tested them at a range of retention intervals, from 1 to 72. h. Manipulated rates of change influenced learning and sampling rates: subjects sampled more and learned more quickly in the high change condition. Tests of retention revealed significant interactions between retention interval and the experienced rate of change. We observed a striking and surprising difference between the high and low change treatments at the 24. h retention interval. In agreement with earlier work we find that a circadian retention interval is special, but we find that the extent of this 'specialness' depends on the subject's prior experience of environmental change. Specifically, experienced rates of change seem to influence how subjects balance recent information against past experience in a way that interacts with the passage of time.
Bibliographical noteFunding Information:
We thank Mark Peterson, Carmen Silvers, Heather Oehler, and Caleea Vann for help with wrangling the blue jays. We also thank Marco Vasconcelos and our anonymous reviewers. This project was funded with support from the Ecology, Evolution, and Behavior Department and the Center for Cognitive Sciences at the University of Minnesota, and by a Florence Rothman Fellowship to ASD. ASD was supported during the experiment by NIH training grant T32 HD007151 to the Center for Cognitive Sciences at the University of Minnesota, and during the writing by an NIH IRACDA-funded PERT fellowship through the Center for Insect Science at the University of Arizona. This project was approved by the Institutional Animal Care and Use Committee of the University of Minnesota.
Copyright 2012 Elsevier B.V., All rights reserved.
- Environmental change