Evolutionary Roots of Motor Planning: The End-State Comfort Effect in Lemurs

Kate M. Chapman, Daniel J. Weiss, David A. Rosenbaum

Research output: Contribution to journalArticlepeer-review

42 Scopus citations


Humans (Homo sapiens) anticipate the consequences of their forthcoming actions. For example, they grasp objects with uncomfortable grasps to afford comfortable end positions-the end-state comfort (ESC) effect. When did such sophisticated motor planning abilities emerge in evolution? We addressed this question by asking whether humans' most distant living primate relatives-lemurs-also exhibit the ESC effect. We presented 6 species of lemurs (Lemur catta, Eulemur mongoz, Eulemur coronatus, Eulemur collaris, Hapalemur griseus, and Varecia rubra) with a food extraction task and measured the grasp used-either a canonical thumb-up posture or a noncanonical thumb-down posture. The lemurs adopted the thumb-down posture when that hand position afforded a thumb-up posture following object transport, thereby exhibiting the ESC effect. We conclude that the planning abilities underlying the ESC effect evolved at least 65 million years ago, or 25 million years earlier than previously supposed based on an earlier demonstration of the ESC effect in cotton-top tamarins (Saguinus oedipus; Weiss, Wark, & Rosenbaum, 2007). Because neither cotton-tops nor lemurs are tool users, the data suggest that the cognitive abilities implicated by the ESC effect are not sufficient, although they may be necessary, for tool use.

Original languageEnglish (US)
Pages (from-to)229-232
Number of pages4
JournalJournal of Comparative Psychology
Issue number2
StatePublished - May 2010

All Science Journal Classification (ASJC) codes

  • Ecology, Evolution, Behavior and Systematics
  • Psychology (miscellaneous)


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