What Makes Us Human (Homo sapiens)? The Challenge of Cognitive
Cross-Species Comparison
Christophe Boesch
Max Planck Institute of Evolutionary Anthropology
Two major theoretical approaches have dominated the quest for uniquely human cognitive abilities: a
developmentalist approach stressing the importance of environmental and social conditions, and a
predominant approach in experimental and comparative psychology, the deterministic approach suggesting
the effect of environmental and social conditions to be minimal. As a consequence, most claims of
human cognitive uniqueness are based on comparisons of White middle class Westerner humans (Homo
sapiens) with captive chimpanzees (Pan troglodytes). However, humans are much more than only White
middle class Westerners, and chimpanzees are much more than only captives. A review of some data
available on different populations of humans and chimpanzees reveals that only the predictions of the
developmentalist approach are supported. In addition, systematic biases are too often introduced in
experiment protocols when comparing humans with apes that further cast doubts on cross-species
comparisons. The author argues that only with consideration of within-species population differences in
the cognitive domains and the use of well-matched cross-species experimental procedures will an
objective understanding of the different cognitive abilities between species emerge. This will require a
shift in the theoretical approach adopted by many in experimental and comparative psychology.
Keywords: human, chimpanzee, comparison, within-species variation, cognition