Factors Modulating the Occurrence of the Selective-Value Effect in Tufted Capuchin Monkeys (Sapajus spp.)

Just like human beings, animals often make irrational choices; that is, when making a choice, they do not maximize the amount of food they can obtain. The selective-value effect occurs when individuals show no distinct preference for high-value food when it is coupled with low-value food compared to when it is presented alone. In the present study, we investigated the occurrence of the selective-value effect in twelve tufted capuchin monkeys (Sapajus spp.) by exploring, for the first time in this genus, both the role of food quality and the time available to consume the food. Overall, capuchins preferred the more abundant food option over the single option. However, at the individual level, some capuchins showed the selective-value effect; that is, they did not show a preference for either option. Both food quality and the time available to consume the food modulated capuchins’ preferences. Our findings suggest that apparent irrational decisions might stem from sensory feedback and the need for nutrient intake maximization.