Phrenology is actually a pseudo-science which focuses on the measurement of the human skull to find correlations amongst specific mannerisms, concepts, and their corresponding locations on the brain (developed by the physician, Franz Joseph Gall in 1796). For example, it may have been believed that a person’s knowledge center was above their left eyebrow, whereas his or her location of “charisma” may rest near his or her left ear. No such relations actually exist, but this didn’t stop Gall’s “phoney-science” from fooling human behaviorists through the early and mid-1800s.
Many scientists through that period thought that human behavior could be more accurately studied by examining specific areas of the brain (as charted on a diagram of a human skull) which would, in theory, perform likewise specific functions.
It was believed that these specific areas of the brain existed in a size proportional to the behavior which it produced in a person. To demonstrate this, consider two different persons. Person A is wildly outgoing while Person B is a miser. A phrenologist from the 1800s would conclude that the portion of the brain responsible for manifesting generosity was much larger in the case of Person A and underdeveloped in the case of Person B.
Many phrenologists drew conclusions that brain areas for specific qualities existed near the body parts to which they are associated. For instance, the parts of the brain thought to be responsible for shape, color, and size recognition were believed to exist near the eyes (because they allow people to perceive these qualities). Similarly, it was often believed that a person's centers for logic and judgement existed near the ears (because a statement must be heard before it can be deciphered or responded to).
By this sort of rationale, it came to believed that an analysis of the skull cavity could show the relative sizes of the different specialized portions of the brain—therefore telling indicating a person’s personality traits and behaviors.
This “science” kept well with many physiologists and behaviorists at the time (becoming especially popular from 1810 to 1840), but lost steam as scientists began to look on it as nonsense. French physiologist Francois Magendie even declared to phrenology to be “the pseudo-science of the modern day” in 1843.
While it is essentially foolishness, phrenology is credited as man’s first step toward modern neuroscience. Phrenology was one of the first sciences to lead people to believe that the brain has specialized parts for specific functions (which, indeed, it does). However, what Franz Joseph Gall failed to realize in 1796 is that these specific functions don’t correlate with singular behaviors or personality traits.
Even the most boring person has the same faculties within his or her brain that the most spontaneous people have in theirs. What makes all humans unique is how we are trained to use them.
One shouldn’t judge 19th century physiologists too harshly though. Were it not for them thinking that a person’s sense of locality rests behind his or her right eyebrow, be might not have come to realize the true ways in which the brain is specialized to serve us.