Left-Handedness and Cognition: New Insights

Does left-handedness affect abilities like creativity or intelligence?

Most people are right-handed, but about 10.6% are left-handed (Papadatou-Pastou and co-workers, 2020). While some older studies suggested that left-handedness may be linked to artistic abilities or intelligence, most recent studies do not show such associations. Handedness, however, is not the only form of left-right asymmetry that people show. One idea that has been suggested is that it is not handedness per se that is linked to cognitive abilities, but how these asymmetries are distributed in the brain. To investigate this, the connection of handedness to cognitive abilities needs to be investigated taking other asymmetries into account.

A new study on handedness and emotion recognition asymmetries

A new study, now published in the scientific journal Scientific Reports focused on exactly this research aim. Scientist Georgina Donati from the Universities of Oxford and London and her research team tested visitors to The Science Museum in London with two tasks (Donati and co-workers, 2024). To test whether the museum visitors were more skilled with their left or right hand, the so-called pegboard task was used. In this task, the museum visitors had to move little colored pegs into holes on a board as fast as possible with each hand. By measuring which hand was faster, it could be determined whether someone was left-handed or right-handed. In addition, a so-called chimeric faces test was conducted. In this task, the museum visitors had to look at pictures of faces that showed emotion on either the left or right half of the face while the half was emotionally neutral. The volunteers had to rate the expressiveness of the emotions that the faces showed. By comparing how expressive they rated the emotion shown on the right or the left half of the faces it could be determined whether people showed a left- or a right-sided bias for emotion recognition. Moreover, the museum visitor performed a test of language fluency and filled out an autism questionnaire on social difficulties. They also gave information on self-reported autism or ADHD diagnosis.

New insights into handedness, emotional lateralization, and cognitive performance

So, what did the scientists find out?

As was to be expected, most people were right-handed. Also, most people found faces with an emotional left half more expressive than those with an emotional right half. This bias for the left half of the face concerning emotion recognition is well recorded in the scientific literature.

The scientists then analyzed how handedness was linked to success in the pegboard task and found that people with moderate handedness were most successful, independent of whether they were left-handed or right-handed. Task success was also linked to language fluency, showing that there may be a cascading effect between handedness, task success, and cognitive ability.

The scientists then further tested whether the laterality profile of an individual volunteer had any effects. Overall, 53% of volunteers showed the standard profile (right-handed and left-dominant for visual emotion recognition). 12% of volunteers showed a reversed profile. 13% showed a left bias for both tests and 22% of volunteers had a right bias for both tests. Interestingly a reversed profile was linked to both more self-reported social difficulties and a higher self-reported rate of autism and ADHD. The scientists argued that people with the reversed profile do not align with the average of other people for both handedness and emotional lateralization, which may it make more difficult for them to properly time their reaction to social cues and may thus lead to social difficulties.

Conclusion

This finding shows that it may not be left- or right-handedness itself that is relevant to cognitive abilities but more the profile of different asymmetries. This means that for future projects on left-handedness and other abilities, it would be important for scientists to consider the overall asymmetry profile beyond handedness, too.

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