Target animacy influences chimpanzee handedness

Area of Science:

• Primatology
• Comparative Psychology
• Neuroscience

Background:

• Hand preference in great apes is influenced by object type.
• Previous research on gorillas indicated a right-hand bias for inanimate targets, but not animate ones.

Purpose of the Study:

• To investigate handedness in chimpanzees (Pan troglodytes) using a similar method to previous gorilla studies.
• To determine if chimpanzees exhibit a similar pattern of hand preference based on target object animacy.

Main Methods:

• Employed a quantitative, bottom-up approach using focal follow video sampling.
• Assessed frequencies and proportions of lateralized hand actions toward animate and inanimate targets in nine captive chimpanzees.
• Utilized identical methodology to prior investigations of gorilla handedness.

Main Results:

• Chimpanzees demonstrated a significant right-hand bias for actions directed toward inanimate targets.
• No significant right-hand bias was observed for actions directed toward animate targets.
• This pattern was consistent at both the group and individual levels for most subjects.

Conclusions:

• The findings suggest that a right-hand bias in chimpanzees is specific to inanimate objects.
• This object-specific handedness may reflect left-hemisphere dominance for processing functional properties of inanimate objects.
• A population-level right-hand bias might be an ancestral trait inherited from a common human-ape ancestor, not unique to humans.