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Foraging choice in laboratory rats: Constant vs. variable delay.
S D Zabludoff1, J Wecker2, T Caraco3
1The Johns Hopkins University, School of Hygiene and Public Health, Department of Population Dynamics, 615 North Wolfe Street, Baltimore, Maryland 21205, U.S.A.
Behavioural Processes
|June 5, 2014
Summary
Rats chose between constant and variable food delays. While initially preferring constant delays, their preference shifted to variable delays as the mean delay increased, supporting reward discounting models over energy budget models.
Area of Science:
- Behavioral Economics
- Animal Behavior
- Foraging Theory
Background:
- Animals often face choices between immediate, certain rewards and delayed, uncertain rewards.
- Models of foraging behavior predict different preferences based on reward timing and energetic needs.
Purpose of the Study:
- To compare predictions of two models of foraging choice: a discounted future rewards model and an energy budget model.
- To investigate how laboratory rats choose between constant and variable delays for food rewards under varying physiological states.
Main Methods:
- Laboratory rats (Rattus norvegicus) were presented with choices between constant and variable delays for food availability.
- Mean delays were systematically varied, and subjects' body weight was manipulated to simulate different energetic states.
- Preference was measured by observing choices between the two delay options.
Main Results:
- Rats initially preferred constant delays but shifted to preferring variable delays as the mean delay increased.
- Preference for variable delays persisted even as the mean delay was decreased.
- Short-term body weight changes did not significantly affect delay preference.
Conclusions:
- The observed pattern of preference is more consistent with the predictions of a discounted future rewards model.
- The energy budget model, which predicts constant delay preference at high feeding rates, was not fully supported.
- This study provides empirical evidence for the influence of delay variability on foraging decisions in rats.
