Abstract # 1015 Poster # 173:

Scheduled for Friday, August 19, 2005 07:00 PM-09:00 PM: (Cambridge/Oxford Room) Poster Presentation


J. L. Russell, H. Freeman, E. Reynolds and W. D. Hopkins
Div. of Psychobiology, Yerkes Reg. Prim. Res. Ctr., Atlanta, GA 30322, USA
     In humans and other primates, there is some evidence of right hemisphere asymmetries in facial expressions associated with emotions. Self-directed behaviors, such as scratching, have been examined in both pharmacological and ethological studies investigating emotional responses to social anxiety. Although many studies have examined scratching as an indicator of stress, few have looked at lateral biases in this behavior. In this study, we examined the hand used for scratching and the side of the body that was scratched by 60 chimpanzees during a video that produced low-level social anxiety versus a baseline observation period. The video was 30 minutes long and showed groups of chimpanzees consuming watermelon. The chimpanzees in the video produced food barks, screams, and submissive grunts as they negotiated with one another over possession and sharing of the watermelon. Scratching was characterized as rubs, gentle scratches, and rough scratches. The video condition significantly increased scratching compared to the baseline condition t(59) = 5.97, P < 0.001. With respect to laterality, there were no significant differences in hand preference for scratching between the baseline and video conditions. However; the chimpanzees showed a significant leftward shift during the video condition for the side of the body scratched compared to the baseline condition t(59) = -2.23, P < 0.05. Because the somatosensory afferent pathways project contralaterally, these data support previous studies in chimpanzees which have shown that behaviors associated with emotionality are lateralized to the right hemisphere. Supported by NIH grants NS-36605 and NS-42867.