Mental faculties and personality traits can be determined by analysing the shape and bumps of the human skull, with different brain regions responsible for specific abilities.
Phrenology, developed by Franz Joseph Gall in 1796, was popular in the 19th century but has no scientific validity. While it correctly proposed that different brain regions have different functions, the phrenological maps were entirely speculative and skull shape bears no relationship to personality or mental ability. Modern neuroscience, particularly fMRI and other brain imaging, has mapped actual brain functions but found no support for phrenological claims.