That's the finding of a new study examining the link between cognitive ability and handedness. Lefties score consistently lower on aptitude tests than righties, and left-handedness is cognitively equivalent to being born prematurely. Yeah...this one's going to be controversial.
Flinders University professor Mike Nicholls - who is himself left-handed, for whatever that's worth - led a recent study examining the difference between right-handers and left-handers throughout the English-speaking world. His conclusion is that the commonly held notion that lefties are more likely to be gifted is, in his own words, "a myth":
"The evidence, based on our analyses of very large databases of handedness and other attributes in people across Australia, the UK and the USA, doesn't bear out that myth. Our study of members of the same family confirms that left-handed children will do worse than their right-handed siblings."
Obviously, we should keep in mind some pretty major caveats here - this study is only talking about broad trends, and a person's handedness is only one of several factors that determines cognitive ability. Obviously, there are tons of brilliant left-handed people, but what this study suggests is that all that might be despite their left-handedness, and certainly not because of it, as has been suggested. And this is just one study - for something as big as this, which is essentially saying a large swath of the population suffers from a form of previously undiagnosed cognitive impairment, we'll want to see plenty more evidence before we put too much stock in it.
So then, why does this discrepancy exist? Well, according to Nicholls, it's all comes down to how different parts of our brains are specialized to perform certain tasks. The left hemisphere of the brain - which controls the right hand, and so is associated with right-handedness - is responsible for more tasks than the right, and that's what puts lefties - who have stronger connections on the right side of brain - at a cognitive disadvantage. Nicholls explains:
"Left and right could so easily be the same in humans and in some animal species it is the same. In humans, though, there seems to be this large specialisation of the two sides of the brain. It is most likely related to squeezing as many eggs as possible into one basket.