Abstract # 140:

Scheduled for Friday, June 22, 2007 05:00 PM-07:00 PM: Session 14 (South Main Hall) Poster Presentation

Consistency of Hand Preference Across Unimanual and Bimanual Tasks in Capuchin Monkeys (Cebus apella)

A. L. Lilak and K. A. Phillips
Hiram College, Department of Psychology, Hiram, Ohio 44234, USA
     Numerous studies investigating behavioral lateralization in capuchins have been published. While some research groups have reported a population-level hand preference, other researchers have argued that capuchins do not show hand preference at the population-level. We tested eleven brown capuchin monkeys (Cebus apella) to determine if they show consistent hand preferences across two unimanual and four bimanual tasks. Capuchins were expected to display high intertask consistency across the bimanual tasks but not the unimanual tasks. Most individuals showed significant hand preferences for each task. However, capuchins displayed consistency of hand preference only across tasks requiring similar motor actions, which included the two unimanual tasks [r(10)=0.81, p<0.05] and two of the bimanual tasks [r(10)=0.92, p<0.01]. None of the tasks elicited a group-level hand preference. The magnitude of hand preference was determined by calculating the absolute mean handedness index (ABS-MHI) for each subject on each task. The magnitude of hand preference for the combined bimanual tasks was greater than that for the combined unimanual tasks [paired t-test, t(10)=4.11, p<0.05]. Thus, bimanual tasks elicited a stronger hand preference than did unimanual tasks. These results contribute to the growing database of capuchin laterality and provide additional evidence that this species does not display population-level hand preference.