Chimpanzees are right-handed when recording bouts of hand use

Whether nonhuman primates exhibit population-level handedness remains a topic of considerable debate. Previous research has shown that chimpanzees are right-handed when frequencies of hand use are recorded but some have questioned the validity of this approach. In this study, we evaluated handedness in 180 captive chimpanzees for a task measuring bimanual actions. Bouts rather than frequency of hand use were recorded in each subject. Population-level right-handedness was found using both continuous and nominal scales of measurement. Neither sex nor rearing history had a significant effect on hand use. These results indicate that chimpanzees are right-handed, even when using a more conservative measure of handedness. Limitations in the use of bouts in handedness assessment are also discussed.