Risk sensitive foraging by rats in the operant arena
Master of Arts
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The operant arena was used as the framework in which to study the theory of risk-sensitivity, A small colony of hooded rats was exposed to increasing work demands while given the choice between simultaneous fixed ratio (risk-averse) and variable ratio (riskprone) schedules. The four rats were maintained in a large arena with access to eight feeding stations for two 30-minute sessions per day. Stations on one side of the arena were programmed to pay off on a fixed ratio, while those on the other side paid off on a variable ratio. The subjects were exposed to ratio value schedules 5, 10, 2 0, 40, and 80 in an ascending sequential order; each schedule was in effect for seven consecutive days. Dispersion patterns, transition types, reinforcements, and the observed preference for working on the FR or VR side of the arena were studied. Throughout the experiment the rats showed an overwhelming preference for the FR side of the arena. However, there was a gradual decrease in the magnitude of the preference for the FR side of the arena over the course of the experiment. It is therefore concluded that as the cost of food increased rats became more risk-prone in their foraging preference. It is also suggested that had the animals been allowed to experience a negative net energy budget (i.e., starvation) a more powerful effect would have emerged.