Why are some people left-handed?

<p>Why are some people right-handed and some are left-handed? And what’s up with some people being ambidextrous (equally good with both hands)? Why, in the past, did some people try to make left-handed people use their right hands? We talk with Chris McManus, professor and author of the book <em><a href="http://www.righthandlefthand.com/" rel="nofollow" target="_blank">Right Hand, Left Hand: The Origins of Asymmetry in Brains, Bodies, Atoms, and Cultures</a></em>. We’ll even find out how common left-handedness (or left-pawedness) is in other animals!</p> <p>Download our learning guides: <a href="https://npr.brightspotcdn.com/1c/06/1410b5c740b39fca31c01574fb7b/why-are-some-people-left-handed.pdf" rel="nofollow" target="_blank">PDF</a> | <a href="https://docs.google.com/presentation/d/1z6BuvHs3m4p3DDSVza6wQXt4m7o_LpYCF03eEcTFPs4/copy" rel="nofollow" target="_blank">Google Slide</a> | <a href="https://npr.brightspotcdn.com/6d/77/a72aa5ff4319b22716c6f6589af3/butwhy-178-handedness-transcript.pdf" rel="nofollow" target="_blank">Transcript</a></p> <ul> <li><p>Why do we prefer one hand over the other? McManus says it probably pays to specialize. It’s better to do something with one hand over and over and get really good at it, as opposed to doing it sometimes with one hand and sometimes with the other. For example, it takes years to develop your handwriting, so it would take twice as long to develop good handwriting with both hands!</p></li> <li><p>How do we pick which hand? We chose the hand that feels more normal to us, and then we practice with that hand. Try a simple experiment: bring your hands together quickly and entwine your fingers like you’re holding hands with yourself. Which thumb do you have on top? Now switch which thumb is on top. It probably feels a bit wrong.</p></li> <li><p>90 percent of people use their right hand more. Our brain is asymmetrical (different on the right and left sides), and most of us use the left half of our brain to talk. Our heart is also on the left side of our body for most human