Lateralized scratching in chimpanzees (Pan troglodytes): Evidence of a functional asymmetry during arousal

William D. Hopkins, Jamie L. Russell, Hani Freeman, Elizabeth A.M. Reynolds, Caroline Griffis, David A. Leavens

Research output: Contribution to journalArticle

19 Scopus citations


This study evaluated laterality in scratching by chimpanzees (n = 89) during socially arousing circumstances. Hand use and the side of the body scratched was recorded during a baseline and experimental condition. In the experimental condition, chimpanzees were shown a video of other conspecifics sharing, fighting over, and consuming a watermelon. Self-touches were categorized as either rubs or scratches. The chimpanzees showed a significant right hand bias for rubbing and also significantly directed the rubs to the right side of the body. For scratching, the chimpanzees showed no hand preference but a significant bias for scratching on the left side of the body. These results support the view that the right hemisphere regulates the autonomic nervous system during arousal.

Original languageEnglish (US)
Pages (from-to)553-559
Number of pages7
Issue number4
StatePublished - Nov 1 2006



  • Arousal
  • Chimpanzee
  • Emotional contagion
  • Laterality
  • Scratching

ASJC Scopus subject areas

  • Psychology(all)

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