Turney then makes two simple observations.  First, every human pupil is dark brown, regardless of the color of the iris, which encloses the pupil and determines the color of the eye.  Second, blue is the lightest color of human iris.  The consequence of these two observations is that the size of the pupil is easiest to determine in blue eyes.  If you face people with different eye colors and must determine whether each person likes or is interested in you, with all else equal, it is easiest to read the blue-eyed person’s level of interest or attraction.

Turney’s argument, which I believe might be true, is that blue-eyed people are considered attractive as potential mates because it is easiest to determined whether they are interested in us or not.  It is easier to “read the minds” of people with blue eyes than of those with eyes of any other color, at least when it comes to interest or attraction.