Choice among Equally Priced Food Alternatives in Rats
Gonto (Burnette), Kelsey Leigh
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Studies investigating unit price predictions of choice in humans and monkeys have indicated that – at relatively cheap prices – most subjects prefer a large reward for more work than a small reward for less work; however, the opposite pattern has been reported in pigeons. Our study further explored this issue by examining rats’ demand and choice between alternatives equal in price but comprised of different response requirements and reinforcer magnitudes. Five food-restricted adult male Long Evans rats lever pressed for food pellets. Demand curves were first obtained by manipulating the fixed-ratio (FR) response requirement across sessions using 1-pellet and 4-pellet reinforcers. In the choice phase of the study, two levers were available simultaneously. In most conditions, the alternatives were equally priced but comprised of FR and reinforcer sizes of differing magnitudes. Two patterns of results were exhibited: rats either displayed a clear preference for one of the alternatives or they showed a lever bias. The rats with lever biases demonstrated a clear preference for the cheaper alternative during conditions in which the alternatives were unequally priced. Rats demonstrating preference under equally priced choice comparisons tended to prefer the larger magnitude alternative over the smaller one until the overall price became expensive. These results provide mixed support for unit-price predictions of choice, which state that, when two alternatives of equal unit price are available, there should be no discernable preference between them. This study demonstrates that some rats do, in fact, exhibit a preference between equally priced alternatives comprised of different response requirements and reinforcer amounts.