Mere existence left-handedness seems to contradict Darwin. According to the theory of evolution through natural selection (to put it very simply), a species should retain the features necessary for survival and reproduction, and discard those that are not very useful. Yet about 10 percent of people continue to develop greater left-hand dexterity, a rate that has remained stable throughout history. Why do humans still retain this special ability?
The study, conducted by researchers at the University of Chieti-Pescara in Italy, aimed to confirm the hypothesis that while right-handed people have an advantage in cooperative behavior, left-handed people – especially men, according to the study – have an advantage in competitive behavior, especially in one-on-one situations. This hypothesis is based on the evolutionarily stable strategy (ESS), a concept from game theory applied to evolution.
The ESS thus explains why the percentage of left-handed people remains low but constant. If almost everyone in the population is right-handed, being left-handed confers a frequency-dependent advantage: being in the minority, left-handers are less predictable in competitive interactions (e.g., in a boxing match), which can translate into a slight advantage (left hook!). However, if left-handedness becomes very common, this advantage will disappear as others adapt to encountering left-handers with the same frequency. In evolutionary terms, a “stable equilibrium” is achieved when the majority are right-handed and the minority are left-handed, because neither “strategy” can completely eliminate the other, as their advantages vary depending on the frequency of each in the population.
How can research support this hypothesis? Italian researchers conducted two experiments to see if hand dominance was associated with any particular personality type. Results were recently published in the scientific journal Scientific Reports.
Right vs. left
In the first experiment, approximately 1,100 participants completed questionnaires designed to measure their handedness (the level of dexterity between one hand and the other) and various aspects of competitiveness, such as a tendency to achieve personal goals or an aversion to fear-driven competition. The results showed that people who identified as more left-handed showed higher levels of personal development-oriented competitiveness and lower levels of anxious avoidance. This means that left-handed people were more likely to engage in competitive situations than right-handed people.
Moreover, when highly lateralized groups (only southpaws, no ambidexterity) were compared, left-handers scored higher on “hypercompetitiveness,” a trait that suggests an intense desire to win, even at the expense of others.
In the second experiment, a subgroup of 48 participants (half right-handed, half left-handed, equal proportions of men and women) took the pegboard test, a classic laboratory test measuring manual dexterity. Interestingly, no significant differences were observed here either between left-handed and right-handed people, or between measures of lateralization and competitiveness scores. This suggests that hand preference and competitiveness are not directly related to motor skills.
Give them a hand
According to the study’s authors, left-handedness is not just a biological coincidence, but a feature that may provide an advantage in the context of competition and is therefore worth protecting. This supports, at least in part, the idea that the unequal split between right-handers and left-handers can be maintained through evolutionary balance. While the right-handed majority favors social cooperation, the left-handed minority benefits in competitive contexts where surprise plays a role.
But what about other personality types? Are left-handed people more extroverted or more emotionally unstable? The study cited here did not show significant differences between left-handed and right-handed people in terms of the Massive Five personality traits (openness, conscientiousness, extraversion, agreeableness and neuroticism). There was also no relationship between handedness and the level of depression or anxiety in this sample of people without a psychiatric diagnosis. This suggests that the advantage associated with left-handedness is more related to competitiveness than to general differences in personality or mental health.
The study also examined gender differences. Men generally scored higher on hypercompetitiveness and growth-oriented competitiveness, while women showed a greater tendency to avoid competition due to anxiety. This suggests that the interaction between hand preference, competitive profile, and gender is complicated and likely influenced by multiple biological and environmental factors that require further study.
This story originally appeared on WIRED in Spanish and was translated from Spanish.