Final answer:
Franz Gall further assumed that specific mental faculties correspond to localized brain areas and that the size of these areas, reflected as skull bumps, indicate the faculty's strength. This led to the development of phrenology, which is now considered pseudoscience.
Step-by-step explanation:
Franz Gall assumed that the brain is the organ of the mind, and that certain mental faculties correspond to localized areas of the brain. He proposed that the strength of each mental faculty could be determined by the size of its corresponding area of the brain, with these sizes reflected externally as various shaped and sized bumps on the skull.
This field, known as phrenology, was Gall's attempt at linking physical characteristics of the skull to personality traits and mental abilities. It postulated that one could assess an individual's character and cognitive capabilities simply by measuring and feeling the bumps on their head. Despite its initial popularity, phrenology lacked empirical support and is now recognized as a pseudoscience.