The density bias: Capuchin monkeys (Sapajus apella) prefer densely arranged items in a food-choice task.

In the current work, we investigated whether capuchin monkeys preferred densely distributed resources to sparsely distributed resources in a 2-choice discrimination task with edible rewards. Capuchin monkeys were biased to select a denser food set over the same number of food items in a sparsely arranged set. Furthermore, increased density of the larger food set facilitated discrimination performance in quantity comparisons with a true difference in set size.