Abstract # 86:

Scheduled for Thursday, August 17, 2006 07:00 PM-09:00 PM: Session 8 (Regency West 1/3 ) Poster Presentation

Rearing is Not a Determinant of Chimpanzee Manual Laterality

A. Kocher1 and W. C. McGrew2
1Miami University, Department of Anthropology, Oxford, Ohio 45056, USA, 2University of Cambridge
     Manual laterality in chimpanzees (Pan troglodytes) is highly debated. Observational (ethological) studies of a wide range of spontaneous behavioral patterns in wild chimpanzees show ambilaterality, except for tool use. Experimental (psychological) studies of a few, induced behavioral categories in captive chimpanzees in laboratories show weak but consistent right-preference. One hypothesis to account for this difference is human influence. As humans are overwhelmingly right-handed, right-bias may have been acquired by chimpanzees raised by humans. We used both spontaneous behavioral patterns and an experimental task (Tube Task) to investigate the laterality of 25 adult chimpanzees housed at the Primate Foundation of Arizona. Groups of 5 subjects in each of 5 graded rearing categories based on age of permanent separation from their mother were observed. Rearing categories ranged from human rearing from birth to no human rearing. Data were collected using focal-subject sampling. Spontaneous behavior in 13 categories was recorded using bouts and the bimanual tube task was tested using both bouts and events. Kruskall-Wallis one-way analysis of variance showed there was no significant difference between the rearing categories in hand use shown in spontaneous behavioral categories, nor in the Tube Task using bouts, nor in the Tube Task using events. Thus, it seems unlikely that human influence during hand-rearing of apes can account of any right-biased performance. Funding provided by Rebecca Jeanne Andrew Memorial Fund (Miami University).