Good grades signal good study skills and hard work, high intelligence and aptitude, or all of the above, which are all attributes that help students succeed in college. Signals such as high grades—or a peacock’s tail or big bank building—don’t indicate interest; they are marks of desirability. That is, the gaudy tail doesn’t signal how much the peacock is interested in a particular peahen; it signals how much the hens should be attracted to that particular cock.
