During foraging decisions, animals often make irrational choices. The selective-value effect refers to the lack of preference for an option consisting of one highly preferred item plus one less preferred item compared to a single highly preferred item. A similar bias is the less-is-better effect, in which individuals prefer a single highly preferred item rather than an option that includes both a highly preferred item and a less preferred one. Here, we investigated the occurrence of these decisional biases in twelve tufted capuchin monkeys (