Dr. Silvia Paracchini FRSE is a geneticist and lecturer at the School of Medicine, University of St. Andrews in Scotland.  In March 2018, she began a comprehensive study on handedness involving nearly 2.4 million participants.  The results were published this week.

She tested only Europeans.  European children are encouraged to use their natural hands, so doing a Euro-centric study actually removes a bias.  Most religions, countries and cultures in other parts of the world (Africa, Asia, Eastern Europe, South America) still consider it acceptable to abuse left handed children (forced hand switching).

The article cited below does not say whether the effect of right handed bias of mass manufacturing was taken into account.  It would also be worth knowing the different rates amongst various groups.  Other studies have claimed XY people are more likely to be left handed than XX, and LGBTQIA people are more likely than cishetero binaries.

World’s biggest study of left-handedness

Thursday 2 April 2020

From Leonardo da Vinci to Oprah Winfrey, and from Napoleon Bonaparte to Jimi Hendrix the talents of left-handers have been celebrated across the generations.

However, the prevalence of people who favour their left hand over their right has always been a rough estimate – until now.

In the biggest ever global study of handedness researchers from across Europe, led by the National and Kapodistrian University of Athens and in the UK by the University of St Andrews, have concluded that 10.6% of the world’s population are left handed.

Details of the study of more than two million people by researchers at the National and Kapodistrian University of Athens, University of Oxford, University of Bristol, Ruhr University Bochum and St Andrews are published in Psychological Bulletin today (Thursday 2 April 2020).

Frequency of left-handedness has shaped and underpinned different fields of research, from cognitive neuroscience to human evolution. While hundreds of empirical studies have assessed handedness, there has never been a large-scale, comprehensive review of the prevalence of handedness and the factors which moderate it.

For the study researchers examined five meta-analyses involving 2,396,170 individuals on hand preference for different manual tasks. They showed that left-handedness prevalence lies between 9.34% using the most stringent criterion of left-handedness, to 18.1% using the most lenient criterion of non-right-handedness, with the best overall estimate being 10.6%.

Typically handedness is measured by which hand is used to write with. However, for this study researchers allowed for the fact that about 9% of people use different hands for different tasks which further improved the accuracy for their findings.

Understanding handedness contributes to our understanding of human evolution. For example, it has been claimed that right-handedness, along with the capacity to make and use tools, to use language, and to show functional and anatomical cerebral specialisation, are characteristics specific to humans, and that they are intimately tied together in the divergent evolution of man from apes.

The lead UK author of the study, Dr Silvia Paracchini, of the School of Medicine at St Andrews, said: “This study will provide a useful reference for different areas of handedness research. In addition to providing reliable figures, the study highlights variability across studies depending on the different criteria used to measure handedness. While we intuitively classify handedness as a left/right category, these data show that the proportion of people using different hands for different tasks is almost as big as the proportion of the left-handers.”

‘Human handedness: A meta-analysis’ is published in Psychological Bulletin.

Please use the paper’s DOI (10.1037/bul0000229) in all references and social media posts.

Now if only ignorant and bigoted attitudes will finally die.

I don’t care if your culture, society or religion says it’s “rude” to do or hand you something with my left hand, I’m still going to do it.  There’s nothing wrong with my hand, it’s your unfounded beliefs that are wrong.