Great Apes Do Not Learn Novel Tool Use Easily: Conservatism, Functional Fixedness, or Cultural Influence?

Abstract

Animal culture has been of interest for decades but the concept remains controversial. Many researchers feel that animal behavior should not be granted the label “culture” because the latter includes more than “simple” behavioral variation. In recent years, the study of animal culture has been concerned mainly with social learning mechanisms, often claimed to be human specific, which led to the uniqueness of human culture. In addition, failure to innovate novel cultural behavior as often as humans is usually explained by psychological mechanisms presented as more parsimonious, such as conservatism or functional fixedness. However, it is unclear how cognitively complex these mechanisms are in the first place. Here, I analyze recent data obtained with wild chimpanzees (Pan troglodytes schweinfurthii) and wild-born orangutans (Pongo abelii) using the honey-trap experiment, in which individuals must devise a solution to reach inaccessible honey. I compare behavior of apes that developed a tool-based solution in the task with those that did not, and test whether conservatism and functional fixedness can explain individual variation in ape behavior. I find evidence of conservatism, with apes relying on their existing knowledge, and evidence of functional fixedness, with this knowledge potentially preventing them from innovating. However, the apes showed large intraspecific variability. I discuss the two mechanisms through a representational perspective to tackle their cognitive complexity. Understanding how conservatism and functional fixedness interact with ape cultural knowledge to limit innovation of novel tool use appears necessary to understand the full extent of ape cultures and how they compare to human cultures.