These and similar questions about left-handers are common but are they really true – Left-Handers
The idea that left-handedness may be related to general intelligence (or any other cognitive ability for that matter) seems to be related to the fact that the origin of hand preference has little to do with the hands themselves. Left-Handers
Unless the person takes any action, it is impossible to judge whether a person is left-handed or right-handed just by looking at their hands.
Left- and right-handed people’s bones, muscles, tendons, and other parts of their hands typically don’t show any noticeable differences.
Instead, the preference for using one hand over the other for fine motor tasks such as writing comes from the brain.
Therefore, it is at least conceivable that genetic or environmental factors that influence brain development in such a way that a person is left-handed may also affect the development of brain areas associated with intelligence.
Are Left-Handed People Really Smarter?
Accordingly, it is not impossible that left-handedness and intelligence are linked. But is it really so? Empirical studies show surprisingly ambiguous results.
Some studies find that right-handed people are more intelligent, while others find the opposite. Such differences between studies are not uncommon in the science of psychology and can often be explained by sample characteristics and specific methods used to assess hand and intelligence.
Therefore, it is difficult to determine the true effect by looking at individual studies.
To finally settle the debate on left-handedness and intelligence, Eleni Ntolka and Marietta Papadatou-Pastou, two researchers from the University of Athens in Greece, conducted a so-called meta-analysis of published studies on left-handedness and intelligence (Ntolka & Papadatou-Pastou, 2018).
A meta-analysis integrates the results of several experimental studies, which has the advantage that the sample size is much larger, increasing statistical power and that the analysis is less likely to be affected by the sample characteristics of individual studies.
Overall, Ntolka and Papadatou-Pastou (2018) integrated the results of 18 studies measuring full IQ scores in different hand groups. In total, data from 20,442 individuals were included.
Three meta-analyses were conducted on possible differences in standardized IQ scores between their groups:
Comparison of left-handed people with right-handed people
Comparison of left-handed and ambidextrous people with right-handed people
Comparison of ambidextrous people with right-handed people
Are Left-Handed People Smarter?
There is no difference in average IQ scores between right-handers and non-right-handers, or between right-handers and mixed people.
There was a statistically significant effect for comparison between right-handers and left-handers, showing that right-handers have a higher average IQ than left-handers.
More importantly, this impact was very small and unlikely to have any significant real-life impact.
Assuming that left-handers have an average IQ of 100 and both left-handers and right-handers have similar variation in their data, right-handers will have an average IQ of 101.05. Also, the effect lost statistical significance when a study was excluded from the meta-analysis.
These findings led the authors to conclude that the absolute magnitude of differences in IQ between left-handers and right-handers is extremely small and that any intelligence differences between the two groups in the general population are negligible.
So no matter what the fun fact sheets on social media tell you: Sorry Left-handers including me, we’re not smarter than the rest of the population in the world.