Handedness during feeding in chimpanzees (Pan troglodytes) at Chimfunshi Wildlife Orphanage, Zambia
Humans are considered unique in their extreme population-level right handedness, seen in no other species to date. Certain behavioral asymmetries have been shown in other animals, especially in nonhuman primates, and these asymmetries are suspected to be closely tied to anatomical asymmetries in the brain and possibly correlated with language and complex thought. Studies of primate hand preference have searched for evidence of population-level handedness for certain tasks as a proxy for brain asymmetries and their potential intellectual correlates. My study examines the hand preference during feeding of 34 chimpanzees living at the Chimpanzee Project Area (CPA) at Chimfunshi Wildlife Orphanage in Zambia. Results indicate that 30 of the 34 subjects exhibit a significant hand preference for unimanual feeding, refuting the commonly held conception that less complex, everyday tasks will not be lateralized. Additionally, data indicate that age, sex, and the presence of family members at the sanctuary all have some effect on the handedness of the subject, though the direction of this effect could not be determined. While many of the chimpanzees at the CPA have diverse and unique backgrounds before entering the sanctuary, this did not appear to have an effect on the handedness of the subject, though a number of unique individuals and potentially influential factors had to be excluded from analyses. Additionally, I suggest standardizing and correcting methodological inconsistencies in studies of handedness by using statistical methods more appropriate to the type of data gathered in such studies. Finally, I review current findings in the field of primate handedness and revisit the significance of such findings in light of the current study.