Studies of facial asymmetry have revealed that the left and the right sides of the face differ in emotional attributes. This paper reviews many of these distinctions to determine how these asymmetries influence portrait paintings. It does so by relating research involving emotional expression to aesthetic pleasantness in portraits. For example, facial expressions are often asymmetrical—the left side of the face is more emotionally expressive and more often connotes negative emotions than the right side. Interestingly, artists tend to expose more of their poser's left cheek than their right. This is significant, in that artists also portray more females than males with their left cheek exposed. Reasons for these psychological findings lead to explanations for the aesthetic leftward bias in portraiture.