Phrenology is a pseudoscience that involves the measurement of bumps on the skull to predict mental traits. It is based on the concept that the brain is the organ of the mind, and that certain brain areas have localized, specific functions or modules. It was said that the brain was composed of different muscles, so those that were used more often were bigger, resulting in the different skull shapes. This provided reasoning for the common presence of bumps on the skull in different locations. The brain "muscles" not being used as frequently remained small and were therefore not present on the exterior of the skull. Although both of those ideas have a basis in reality, phrenology generalizes beyond empirical knowledge in a way that departs from science. The central phrenological notion that measuring the contour of the skull can predict personality traits is discredited by empirical research. Developed by German physician Franz Joseph Gall in 1796, the discipline was influential in the 19th century, especially from about 1810 until 1840. The principal British centre for phrenology was Edinburgh, where the Edinburgh Phrenological Society was established in 1820.
Phrenology is today recognized as pseudoscientific. The methodological rigor of phrenology was doubtful even for the standards of its time, since many authors already regarded phrenology as pseudoscience in the 19th century. There have been various studies conducted that discredited phrenology, most of which were done with ablation techniques. Marie-Jean-Pierre Flourens demonstrated through ablation that the cerebrum and cerebellum accomplish different functions. He found that the impacted areas never carried out the functions that were proposed through phrenology. Paul Broca also discredited the idea when he discovered and named the "Broca's area": the patient's ability to produce language was lost while their ability to understand language remained intact, due to a lesion on the left frontal lobe. He concluded that this area of the brain was responsible for language production. Between Flourens and Broca, the claims to support phrenology were dismantled. Phrenological thinking was influential in the psychiatry and psychology of the 19th century. Gall's assumption that character, thoughts, and emotions are located in specific areas of the brain is considered an important historical advance toward neuropsychology. He contributed to the idea that the brain is spatially organized, but not in the way he proposed. There is a clear division of labor in the brain but none of which even remotely correlates to the size of the head or the structure of the skull. It contributed to some advancements in understanding the brain and its functions.
