What is the study of skull shape and its relation to mental faculties known as?

The study of skull shape and its relation to mental faculties is known as phrenology. This historical concept, which originated in the early 19th century, posits that the bumps and indentations on the skull can provide insights into an individual's personality traits, intelligence, and even moral character. Phrenologists believed that different areas of the brain were responsible for various intellectual and emotional functions, which could be inferred from the contour of the skull.

Phrenology was influential in its time, contributing to the early development of psychology and neuroscience, despite being largely discredited today. Its emphasis on the physical attributes of the skull reflects a more primitive understanding of the brain's relationship to behavior and cognition, paving the way for more refined methods of studying brain function.