One of the first comparative anatomists, Franz Gall made 3 major findings and one theoretical extension.
First, he made thorough anatomical observations of several species and concluded that brain size and mental capacity were correlated; larger brained animals were capable of performing more complex and more varied tasks. Second, emphasized brain localization. He believed that the mind’s faculties (skills, abilities, personality traits) were assigned to local, specialized regions of the brain. In contrast to the view that the brain operates as a single entity (like the heart), Gall maintained that the brain controlled multiple faculties at the same time, each in their respective parts of the brain. Third, Gall differentiated between gray and white matter, correctly identifying gray matter with active neural tissue and white matter as conducting tissue (ganglia).
Gall’s theoretical extension of his research findings is both better known and less scientific. Using a small sample, Gall studied human skulls. He combined his belief in brain localization with the concept of exercise and concluded that the shape of a skull can serve as an index of mental ability. Gall assumed that mental functioning could be determined by observing the variation in skull structure. He assumed that any given skill was correlated with a particular part of the brain. And the better one became at that skill, the more that brain portion would enlarge (eventually forcing the skull to expand as well). Expanded portions (bumps) of the skull, then, were used to diagnosis skills and abilities. Gall called it “cranioscopy.” It is more popularly known as phrenology (coined by Thomas Foster and used by Johann Spurzheim).
In phrenology, the contour of the skull and face also was thought to reflect one’s honesty, integrity and future potential. It assumed that the brain is like a muscle, and that increased use of an a skill or function would build up the area. This flex-your-mental-muscles approach fitted well with the educational approach of “training the mind.” According to this view, the mind could be improved by general education. Reading good literature would help one in every area of life.
The problem with phrenology was that the predictions were vague and self-fulfilling. People were identified as being “friendly,” which too vague to be of much predictive value. Friendly is a difficult behavioral description, since people tend to be friendly in some situations and not in others. The predictions were also self-fulfilling. Not only did people who were characterized as being “careful” tend to act more careful, observers who were told expect “careful” behavior reported seeing it.
Gall identified 26 regions (his followers expanded it to 35). Not only did each region cause a particular behavior, the pattern of regional influence was critical. if a person was diagnosed on the basis of skull shape as being dishonest but in fact was honest in behavior, the explanation was that his dishonesty was being suppressed by one of the other regions. Every variation from prediction was explained by reinterpreting the data.
One of the problems was that Gall used a very small sample. He observed one and generalized to many. Another was that the sample was primarily composed of criminals and mental patients. “Normal” skull shapes were often inferred rather than observed; if most criminals had prominent noses, a small nose was assumed to be characteristic of normal behavior. But the real problem with phrenology was the type of evidence it accepted. Phrenology did not rely on controlled experiments but accepted spurious correlations are prove of cause-effect relationships.
Despite resistance, phrenology was very popular. In 1802 it was banned in Austria as religious heresy. And yet it was so popular that a journal on phrenology was published from 1823-1911.
Check out this video on Psychology and Experimental Physiology.