The effects of reward unpredictability on pigeons' foraging decisions and dopamine's role on pigeons' choice

Abstract

In nature, animals face various anthropogenic and abiotic conditions, which can affect food distribution and availability. Animals have to make right foraging decision to survive under these variable conditions. Mammals’ foraging decisions under uncertainty and the neurobiology behind this mechanism have been discussed in the literature. Even though there is a vast literature on mammals, more information is needed to determine whether birds use the same mechanisms. Experiment 1 and 2 tested the drug free preference of pigeons for a constant over a variable delay option. Then their preference was examined under the systemic administration of a dopamine agonist, apomorphine (Apo). Our results suggest that preference for a variable over a constant delay was insensitive to dopaminergic activity in birds in contrast with mammals. Also, sensitization to Apo was long-lasting and partly independently of Pavlovian conditioning. In Experiment 3, Apo-sensitized and saline pigeons’ drug free preference was examined for a 50% probability option over a 5-s delay option, then again, their preference was observed under the systemic administration of Apo or saline. The Apo-sensitized and saline pigeons showed indifference between two options that shows Apo-sensitization has no effect on the development of a preference for variable-delay and probabilistic schedules of reinforcement.