The next time you're at an art museum, pay careful attention to the portraits. You'll find that the majority portray the subject's face from the left side.
Why? Scientists suspect that it has to do with artists' intuitive sense of how emotion registers on the human face. Each side of the brain controls the opposite side of the body. The right half of the brain governs strong emotions like fear, anger, happiness, excitement, and so on. Because these emotions originate in the brain's right half, it makes sense that they appear more noticeably on the left side of the face. Artists, then, would naturally gravitate towards the more emotionally expressive side of the face.
One notable exception to this trend is Rembrandt, the famous Dutch painter. Rembrandt's portraits of women follow suit-most show the subject's left side. But a solid majority of his male portraits depict the right side of the face. Why would Rembrandt have shown the emotional side of women's faces but tended to do the opposite with men?
In a study of Rembrandt's portraits, James Schirillo of Wake Forest University found that viewers saw the male faces as less agreeable than the female faces. Surprisingly, though, the male portraits that did show the more emotional left side were seen to be the least agreeable and most threatening of all. Perhaps this is because men tend to display emotion in a more aggressive manner than women. Men depicted from the left side come off as less approachable than women.
Rembrandt may have sensed this and painted men from the right side in order to render them as agreeable looking as men can be.