Psychology explains why left-handedness is slightly more common in men and it's not just genetics

Although not unheard of, left-handedness is relatively uncommon, affecting roughly one in 10 people worldwide. But there is another layer to the science: men are more likely to be left-handed than women. Why that difference exists has remained a longstanding question in psychology. Is it driven by genetics, hormones, culture, or a combination of all three?

A large meta-analysis published in Psychological Bulletin suggests the answer isn't simple. After reviewing data from 144 independent studies involving 1,787,629 participants, researchers found that males are consistently more likely to be left-handed than females, although the difference is modest. The findings indicate that biology likely plays a role, but environmental and cultural factors cannot be ruled out.

The study, "Sex Differences in Left-Handedness: A Meta-Analysis of 144 Studies," was conducted by Michael C. Papadatou-Pastou, Julian Martin, Marcus R. Munafò and Geoffrey V. Jones and published in Psychological Bulletin in 2008.

Men were about 23% more likely to be left-handed

After pooling results from nearly 1.8 million participants, the researchers found a consistent pattern across countries and study populations.

The odds of being left-handed rather than right-handed were 1.23 times higher in men than in women, according to the study. Broken down by population, the researchers found that men were 22% more likely to be left-handed in Caucasian samples, 31% more likely in African samples and 60% more likely in East Asian samples.

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In practical terms, this does not mean that most men are left-handed. Instead, it means that left-handedness occurs slightly more frequently among males than females across the general population.

It's not just about genes

Although genetics has long been linked to handedness, the researchers argue that genes alone are unlikely to explain why men are more often left-handed.

Instead, the review points to several possible influences, including biological differences during early development, prenatal hormonal exposure and environmental factors.

The authors note that the findings suggest "that the sex difference in hand preference has its basis in innate biological differences between the two sexes but is also significantly modulated by culturally transmitted social influences."

In other words, handedness appears to emerge from an interaction between biology and the environment rather than a single cause.

How culture may influence handedness

The study also found that the size of the male–female difference wasn't identical across all studies.

Factors such as how handedness was measured, the country where the research was conducted, and the year of publication influenced the reported results. One explanation is that cultural attitudes toward left-handedness have changed over time.

The authors note that previous research has documented social pressure to switch writing from the left hand to the right, particularly in more conservative societies and earlier periods. They suggest such cultural influences may have contributed to lower reported rates of left-handedness and may partly explain differences observed across populations.

At the same time, the researchers found that these cultural factors did not fully account for the overall pattern. The male predominance in left-handedness remained consistent across the large body of evidence included in the review.

The difference persisted across studies

To ensure the findings were robust, the researchers examined whether the results changed depending on several study characteristics.

They looked at participants' ethnicity, age, the method used to assess handedness, publication year, and sampling procedures. While some of these factors influenced the size of the difference between men and women, none eliminated the overall finding that males were more likely to be left-handed.

The researchers also observed that estimates of left-handedness have generally increased in more recent studies, which they suggest may reflect declining social pressure against left-handedness. Even so, the sex difference remained evident.

Rather than attributing the difference to biology alone, the authors argue that both innate biological differences between the sexes and culturally transmitted social influences contribute to the observed pattern.