title: Tool use as a way to assess cognition: how do captive chimpanzees handle the weight of the hammer when cracking a nut?
abstract: Tool use in apes has been considered a landmark in cognition. However, while most studies concentrate on mental operations, there are very few studies of apes' cognition as expressed in manual skills. This paper proposes theoretical and methodological considerations on movement analysis as a way of assessing primate cognition. We argue that a privileged way of appraising the characteristics of the cognitive abilities involved in tool use lies at the functional level. This implies that we focus on how the action proceeds, and more precisely, on how the functional characteristics of the task are generated. To support our view, we present the results of an experiment with five captive chimpanzees investigating the way how chimpanzees adapt to hammers of various weights while cracking nuts. The movement performed in the hammering task is analyzed in terms of energy production. Results show that chimpanzees mobilise passive as well as active forces to perform the compliant movement, that is, they modulate the dynamics of the arm/tool system. A comparison between chimpanzees suggests that experience contributes to this skill. The results suggest that in tool use, movements are not key per se, but only in as much as they express underlying cognitive processes.
authors.affiliation: Ecole des Hautes Etudes en Sciences Sociales, Groupe de recherche "Apprentissage et Contexte", 54 Bd Raspail, 75006 Paris, France. blandine.bril@ehess.fr
authors.forename: Blandine
authors.initials: B
authors.lastname: Bril
authors.forename: Gilles
authors.initials: G
authors.lastname: Dietrich
authors.forename: Julie
authors.initials: J
authors.lastname: Foucart
authors.forename: Koki
authors.initials: K
authors.lastname: Fuwa
authors.forename: Satoshi
authors.initials: S
authors.lastname: Hirata
mesh_terms: D000223:Adaptation, Psychological; D000818:Animals; D005260:Female; D006040:Goals; D008297:Male; D008960:Models, Psychological; D002679:Pan troglodytes / Q000523:psychology*; D011340:Problem Solving; D011582:Psychological Theory; D011597:Psychomotor Performance; D012718:Set, Psychology; D013647:Task Performance and Analysis; D053001:Tool Use Behavior