The abnormal expression of mirth is shown in clownishness, levity, and caricaturing of persons… When excessive it can be restrained by devoting more time to serious and practical principles of science. If deficient it can be cultivated through the study of wit and humor.
~ John T. Miller, Applied Character Analysis
The arch-phrenologist Johann Spurzheim located mirthfulness in a particular corner of the forehead where, he said, Voltaire, Rabelais and Sterne each showed a considerable bulge. It’s a little known fact that all three were solemn and severe children who only developed a sense of humor after years of study.