He developed an early interest in the brain after making a connection between one classmate's odd shaped skull and advanced language abilities.

[5] It is being said, that his first ideas about functional localization came from noticing that classmates who excelled at memory tasks had prominent facial features.

While in medical school, he studied under Johann Hermann and Maximilian Stoll who impressed upon him the importance of natural observation.

[12] Based on his early observations about the skull sizes and facial features of his classmates, Gall developed the theory of Organology and the method of Cranioscopy that would later be known as Phrenology.

Cranioscopy is a method to determine the personality and development of mental and moral faculties on the basis of the external shape of the skull.

Gall believed that the bumps and uneven geography of the human skull were caused by pressure exerted from the brain underneath.

Gall believed there were 27 fundamental faculties, among them were: recollection of people, mechanical ability, talent for poetry, love of property, and even a murder instinct.

Instead of slicing randomly, as had been the practice in previous years, Gall's method involved slow exploration of the entire brain structure and the separation of individual fibers.

French scientist Étienne-Jean Georget accused Gall of stealing Charles Bonnet's basic idea of brain localization that he had written about over 60 years earlier.

However, Napoleon Bonaparte, the ruling emperor, and the scientific establishment led by the Institute of France, pronounced his science as invalid.

Physiologist Jean Pierre Flourens emerged as one of the sharpest critics of Gall's theories, testing them on animals by removing portions of the brains of dogs, rabbits, and birds to examine how the remaining sections functioned.

Flourens published his findings in two separate articles, attacking Gall's theory that the brain acted as discrete parts instead of as a whole unit.

[21] One interesting influence was on psychiatry, where the South Italian psychiatrist Biagio Gioacchino Miraglia proposed a new classification of mental illness based on brain functions as they were conceived in Gall's phrenology.

Even though phrenology is now known to be incorrect, Gall did set the groundwork for modern neuroscience by spreading the idea of functional localization within the brain.

The misuse of Gall's ideas and work to justify discrimination were deliberately furthered by his associates, including Johann Spurzheim.