You’re primarily left-handed if you use your left hand for most activities — even if you tend to write with your right hand. Historically, there used to be a social prejudice against lefties (左撇子) . 【小题1】 But no evidence has suggested lefties are at any sort of physical or psychological disadvantage.

It’s estimated that 8 to 15 percent of the adult population is left-handed. Of course, we now know that handedness is determined by genetics and random chance. What we’re just learning, however, is far more interesting. 【小题2】

Lefties may be quicker thinkers. According to an Australian study published in 2006, left-handed people tend to have faster connections between the right and left sides of the brain. 【小题3】 It accordingly leads to quicker and more efficient information processing.

【小题4】 While less than 15 percent of the general population is left-handed, 25 percent of Major League Baseball players are lefties. Studies have found that lefties seem to have a real advantage in interactive sports, such as boxing, fencing, and baseball. It’s possibly because lefties are able to throw off right-handed opponents who are used to going up against other righties.

Emotions seem to be arranged differently depending on handedness. 【小题5】 That might help to explain why lefties seem to have higher rates of depression and certain other mood disorders.