A pre-K teacher in Oklahoma is making news this week after forcing a left-handed 4-year-old boy to write with his right hand. The boy was sent home from school with an article discussing left- and right-handedness. The article mentions historic attitudes toward left-handedness that associate it with evil and the devil. It's written carelessly enough that it isn't clear whether the writer believes left-handedness is still seen as evil or whether that was only the case in the past.
Regardless, it's surprising that today, in 2015, a teacher would try to force a child to write with his non-dominant hand. Roughly 10 percent of people are left-handed, according Chris McManus, a University College of London researcher who wrote a book chapter on the history and geography of left-handedness.
Scientists generally agree that there is a strong genetic component that determines whether a person is right- or left-handed. But good data on the prevalence of left-handedness has been difficult to find, McManus writes.
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One of the best available data sets on left-handedness comes from a scratch-and-sniff survey of olfactory ability mailed out to millions of National Geographic subscribers in the 1980s.
Go ahead and read that sentence again — it doesn't get any less weird the second time around.
In 1986, National Geographic published a special issue on smell. As McManus recounts it, the issue "was accompanied by a 'scratch and sniff' card, which readers were encouraged to scratch, report what, if anything, they could smell, and then, after completing a brief demographic questionnaire, return the card."
The researchers who created the survey, from the Monell Chemical Senses Center in Philadelphia, thought that smell and handedness might be linked. So they included questions about the dominant hand used for writing and throwing things in their demographic section.
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So, 1.4 million people scratched, sniffed and mailed back their cards. As it turned out there was no link between smell and left-handedness, but the resulting 1.4 million datapoints created the largest dataset of hand preference ever constructed.
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