title: Capuchins (Cebus apella) fail to show an asymmetric dominance effect.
abstract: The asymmetric dominance effect (ADE) occurs when the introduction of a partially dominated decoy option increases the choice share of its dominating alternative. The ADE is a violation of regularity and the constant-ratio rule, which are two derivations of the independence of irrelevant alternatives axiom, a core tenant of rational choice. The ADE is one of the most widely reported human choice phenomena, leading researchers to probe its origins by studying a variety of non-human species. We examined the ADE in brown capuchin monkeys (Cebus apella), a species that displays many other decision biases. In Experiment 1, we used a touchscreen method to elicit choice-based preferences for food rewards in asymmetrically dominated choice sets. In Experiments 2 and 3, we distinguished between different types of judgments and used a free selection task to elicit consumption-based preferences for juice rewards. However, we found no evidence for the ADE through violations of regularity or the constant-ratio rule, despite the similarity of our stimuli to other human and non-human experiments. While these results appear to conflict with existing literature on the ADE in non-human species, we point out methodological differences-notably, the distinction between value-based and perception-based stimuli-that have led to a collection of phenomena that are difficult to understand under a unitary theoretical framework. In particular, we highlight key differences between the human and non-human research and provide a series of steps that researchers could take to better understand the ADE.
authors.affiliation: Department of Psychology, Yale University, 2 Hillhouse Ave, New Haven, CT, 06520, USA.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Cohen
authors.affiliation: Department of Psychology, Yale University, 2 Hillhouse Ave, New Haven, CT, 06520, USA. laurie.santos@yale.edu.
authors.forename: Laurie R
authors.initials: LR
authors.lastname: Santos
mesh_terms: D000818:Animals; D002428:Cebus; D002755:Choice Behavior; D007600:Judgment; D010679:Philippines; D012201:Reward
keywords: Asymmetric dominance effect; Capuchin monkeys; Choice biases; Decoy effect