Clinical neuropsychologists and all psychologists use various methods to understand normal human behavior and brain-behavior relationships. One common way of understanding behavior is by the clinical method, which is basically using abnormal behavior to make inferences about normal behavior. Neuropsychologists often study people with known brain damage or with abnormal behavior and then study their brain post-mortem (this can also be done in vivo now with MRI and other neuroimaging techniques). The clinical method is important because it is one way phrenology is easily disproven.
Phrenology started out as a good idea. Franz Gall was a physician and anatomist. He was a careful scientist and, for his day, an unmatched anatomist. Phrenology started out as the localization of intellectual and emotional functions to various regions of the brain, which idea was partially supported by later research. However, with flawed methods, Gall assumed that what occurred in the brain was also manifest through the skull. In some ways he was correct – there is some degree of relationship between head size and overall intelligence (although this relationship is minimal – there is a better correlation between brain size and intelligence then head size and intelligence). Gall and his followers also incorrectly localized functions, including many personality traits, to various regions of the brain (skull). Another problem with phrenology is that Gall used mainly anecdotal evidence on which to found his theory. He also, instead of trying to disconfirm his theory, only paid attention to stories and evidence that supported his theory. While phrenology started out as legitimate in many ways, it quickly degenerated into little more than pop-psychology. Phrenology was discredited by the mid-1830s but it still had many followers throughout the 1800s.
One was phrenology was discredited was through the clinic method. Researchers like Paul Broca were able to show that damage in certain areas of the brain did produce specific deficits but that these deficits did not correspond with Gall’s theorized cranial areas. After many years of applying the clinical method to brain-behavior, the early tenets of Gall – those of brain localization and contralateral function (each hemisphere controls the opposite half of the body) – have been largely supported. Phrenology has not been supported.