Manual lateralization in macaques: handedness, target laterality and task complexity.

Area of Science:

• Primate behavior
• Evolutionary psychology
• Neuroscience

Background:

• Non-human primates are crucial models for understanding human handedness evolution.
• Existing research on primate handedness often overlooks the interplay of target position, hand preference, and task complexity.

Purpose of the Study:

• To investigate macaque handedness in relation to target laterality, tastiness (motivation), and task complexity.
• To explore how these factors influence hand preference in pig-tailed macaques (Macaca nemestrina).

Main Methods:

• Seven pig-tailed macaques participated in three "two alternative choice" tests (one low-level, two high-level tasks).
• Tests varied in food preference options and task difficulty.
• A simple-reaching test assessed hand preference in a social context.

Main Results:

• Macaques exhibited individual hand preference in both simple and complex tasks, but not in the social reaching test.
• Target position affected hand preference in the low-level task but not high-level tasks.
• Food tastiness (motivation) influenced individual hand preference.

Conclusions:

• Macaque hand preference is influenced by target laterality and individual motivation, particularly in simpler tasks.
• These findings offer insights into the factors shaping handedness in primates, potentially informing human handedness evolution.