According to evolutionary theory, the average value of many physical features should be preferred to extreme values because of normalizing or stabilizing selection. For example, it is a myth that all women prefer extremely tall men. Rather, most women prefer men who are a few inches taller than they are. Thus, the average-sized woman does not prefer basket-ball sized men of 7 feet (although very tall women prefer very tall men). Like height, people with facial configurations close to the mean of the population for each sex should be preferred. Some proponents of evolutionary theory suggest that preferences for attractive faces should be innate and present at birth. Others (us) believe that instead of innate preferences, evolution has built-in a more general-purpose averaging mechanism (see box to right).

According to cognitive information processing theory, the average of a category is preferred over other examples of the category. The average member of a category often is called a "prototype." Much research has shown that infants, children, and adults prefer prototypical members of a category to non-prototypical members. For example, an averaged sized dog is usually rated as a better example of the category of "dog" than is a Great Dane or a Mexican Chihuahua. Similarly, faces that are close to the average facial configuration should be preferred. These faces are perceived as familiar, more "face-like" and as the "best" examples of a category of faces.