Context-dependent decision making in wild rufous hummingbirds

Abstract

Conventional models of decision making assume that animals and humans will evaluate available options based on the benefit that they provide and then choose the option that provides the largest benefit. However, there is evidence that the choices of both animals and humans violate this assumption as the choices that are made can be altered by the context in which decisions are presented. In this thesis I used free–living, foraging rufous hummingbirds (Selasphorus rufus) to investigate the effect of context on the decisions they make. Firstly, I gave birds choices between two preferred options and found that the addition of a third non-preferred option changed their preference when options varied in either two dimensions simultaneously (volume and concentration of sucrose), or in only a single dimension (volume or concentration). I also manipulated the learning context and found that hummingbirds have stronger preferences when options are learned simultaneously than when those same options are learned about sequentially. I also manipulated the experience that birds had of the options prior to the choice and found that birds with prior experience did not make different choices than hummingbirds without prior experience. In addition to work with hummingbirds, I also completed experiments with humans looking at the effect of context on decisions about health of others. I manipulated the yellowness of faces and found that when participants choose between two preferred options the addition of non-preferred options changed their preference. These data demonstrate humans and hummingbirds make irrational choices as the decision making context can change the choices that they make. Current theories of decision making are insufficient to explain context-dependent choices made by hummingbirds.