All great ape species (Gorilla gorilla, Pan paniscus, Pan troglodytes, Pongo abelii) and two-and-a-half-year-old children (Homo sapiens) discriminate appearance from reality.

Journal Article (Journal Article)

Nonhuman great apes and human children were tested for an understanding that appearance does not always correspond to reality. Subjects were 29 great apes (bonobos [Pan paniscus], chimpanzees [Pan troglodytes], gorillas [Gorilla gorilla], and orangutans [Pongo abelii]) and 24 2½-year-old children. In our task, we occluded portions of 1 large and 1 small food stick such that the size relations seemed reversed. Subjects could then choose which one they wanted. There was 1 control condition and 2 experimental conditions (administered within subjects). In the control condition subjects saw only the apparent stick sizes, whereas in the 2 experimental conditions they saw the true stick sizes as well (the difference between them being what the subjects saw first: the apparent or the real stick sizes). All great ape species and children successfully identified the bigger stick, despite its smaller appearance, in the experimental conditions, but not in the control. We discuss these results in relation to the understanding of object permanence and conservation, and exclude reversed reward contingency learning as an explanation.

Full Text

Duke Authors

Cited Authors

  • Karg, K; Schmelz, M; Call, J; Tomasello, M

Published Date

  • November 2014

Published In

Volume / Issue

  • 128 / 4

Start / End Page

  • 431 - 439

PubMed ID

  • 25150962

Electronic International Standard Serial Number (EISSN)

  • 1939-2087

International Standard Serial Number (ISSN)

  • 0735-7036

Digital Object Identifier (DOI)

  • 10.1037/a0037385


  • eng