Phrenology. This strange practice was common back in the 1800s, and involved using the bumps and contours of your skull to determine various personality traits and psychological tendencies.
The idea was that the brain consisted of segments, each responsible for a single trait, like concentrativeness (the ability to concentrate) or combativeness (the tendency to fight).
And because the size of these segments hypothetically affected the shape of the skull (a segment larger than others would mean you had more of that trait, and vice versa), observing the shape of the skull would allow phrenologists to psychologically analyze their patients.
Did it work? No. It’s a pseudoscience.
However, the individual who pioneered phrenology, the Viennese physician Franz Joseph Gall, wasn’t too far off: as we all now know, the brain is segmented, with areas that control specific functions, including localized areas responsible for emotions and personality. So his idea was nonetheless influential to modern science.
As far as phrenology goes, though, these traits can’t be discerned by feeling the shape of the skull.
If you’d like to read more about phrenology and its history, I recommend heading over to History of Phrenology on the Web.