Of eyes and hands: Assessing the evolutionarily stable strategy of human handedness by means of eye‐tracking

Abstract

An evolutionarily stable strategy (ESS) suggests that the 1:9 ratio of left- to right-handers in humans could reflect a frequency-dependent equilibrium: the minority of left-handers and the majority of right-handers may have an advantage in competitive and cooperative circumstances, respectively. To evaluate this account, we recorded eye movements during a 'friend or foe' variation of a Go/NoGo task in 24 left- and 24 right-handed participants. Stimuli were silhouettes carrying either a food item (cooperation with a 'friend') or a weapon (competition against an 'enemy') in one hand, and participants were asked to save the friend or to hit the enemy. A better performance emerged in competitive than cooperative trials, confirming the 'weapon effect' (highest efficiency in detecting threatening stimuli), and for right- than left-handed stimuli, confirming an advantage in responding to the most frequent handedness phenotype. Left/right-handed stimuli were better categorized in the competition/cooperation trials and first saccades were faster towards left- than right-handed stimuli, particularly when these were males. We interpret this pattern as an attentional bias favouring earlier orienting to potentially more threatening targets, left-handed males. Results are discussed as partially supporting the ESS and other evolutionary biases, which might be associated with the handedness distribution of humans.

The authors' abstract, as published at the source. British Journal of Psychology, 2026 · DOI ↗