Efeito ‘menos é mais’ em macacos prego (Sapajus spp.): Um teste crítico usando diferentes alimentos igualmente preferidos

Abstract

Under an ideal hypothetical scenario, it is expected that animals prefer options that provide the larger amount or the greater frequency of reinforcement. There is, however, evidence that choice might not optimize gains, such as in the ‘less-is-better’ effect (Hsee, 1998) reported both in humans and nonhumans. In a typical choice preparation, subjects are given a choice between an option that provides a single item of a preferred food and another combo option that offers the same preferred food + a less-preferred food item. Two preference patterns have been documented: Indifference between options and preference for the single-item option, while an influential hypothesis has attempted to account for the latter. The hypothesis of the heuristics of the average states that both food types have positive subjective value, one greater than the other. The value of an option is given by the average of the value of its constituent items, such that the value of the single-item option equals the value of the preferred food, but the value of the combo is lower (for the average of two values is less than the greatest of these values). Hence the preference for the single-item option. Despite being widely accepted, the hypothesis has not undergone critical experimental tests on its tenets. One of these tests involves using different food items that are equally preferred. According to the hypothesis, the animals should be indifferent between options and not prefer the single-item option. The present study implemented this test to test with capuchin monkeys (Sapajus spp.) and the results revealed a clear and marked preference for the option that provides the larger amount of food. This is unprecedented evidence that breaks with the ‘less-is-better’ effect and that demands reviewing current accounts of performance on choice tasks that combine foods of different qualities.