Phrenology was the science of studying the bumps and indentations on a person’s head to determine their predestined station in life. The basic idea was that cranial makeup is reflective of brainpower, and that by examining the shape of the skull and slope of the brow you could discover a patient’s intelligence, strength of character, and likelihood of romantic relationships. Factors such as education, values taught, and whether or not they still had all their teeth were considered secondary in such matters.
Head size was extremely important. The phrenologist would use a caliper (essentially, a big creepy claw) to obtain accurate measurements, and then cross-referenced the results with a detailed medical map which showed the 27 “brain organs”. If your head was a little too big, it meant that you were a common degenerate who was destined to commit multiple murders. If it was a little too small, then you were an ill-bred idiot meant to dig ditches for a living. On those rare occasions where your head size was just right, then you went on to become a phrenologist.
Sadly, phrenology has fallen out of favor with most doctors, who believe that human personality is largely a combination of neurology and environment, and cannot be determined by external physical measures. They obviously have an overlarge cerebral bumpage and should not be trusted under any circumstances.