Complex approaches to handedness and brain lateralization

Abstract

The evolutionary history of the human species reveals a marked progression in brain and upper limb lateralization within the Homo genus. Particularly for tool use and fire control, Homo sapiens evolved with increasingly refined motor abilities, culminating in a strong preference for a dominant hand. Contrary to the common belief that asymmetry may indicate inefficiency or inadaptability, manual lateralization in humans reflects a form of specialization—similar to patterns observed in apex predators—where specialization often confers adaptive advantages. The experience of left-handed individuals in predominantly right-handed societies underscores the need to better understand motor behavior and the mechanisms underlying hand dominance. This experimental study employs a combination of biomechanical metrics and EEG(Eletroencefalografy)-based measurements to analyze general motor behavior during fine motor tasks performed with both hands, specifically handwriting. It further explores how these behaviors evolve over time, with a focus on the emergent dynamics given by permutation entropy measures. Our findings reveal that right-handed exhibit more optimized and stable motor strategies across hands, whereas left-handers and ambidextrous individuals display greater variability and less consistent dominance patterns. However, temporal analyses using permutation entropy of motor behavior revealed similar lateralization profiles between left- and right-handed groups, suggesting functional equivalence in hand use. EEG analyses indicated that right-handers individuals show more distributed and temporally non-linear brain behavior, potentially due to reduced experience or training with the non-dominant hand in daily tasks. We conclude that human lateralization supports a variety of neuromotor configurations and those behavioral patterns are shaped more by usage habits and experience than by intrinsic differences between handedness groups. These findings highlight the evolutionary and functional relevance of motor lateralization in Homo sapiens.