During the 19th and 20th centuries, phrenology was used to determine mental functions and character traits of individuals. Though the practice was thoroughly debunked, for a period, the study of the skull's bumps and contours was widely used in a number of fields, including education, medicine, psychiatry and criminology. Phrenology affected many social issues, such as marriage and the treatment of native populations.
Phrenology claimed to identify abilities and characteristics in several areas. Domestic issues concerned familial love, sexual attraction, friendship, pets and perseverance. It was also thought that phrenology uncovered the existence of very personal traits, including appetites, defensiveness, cautiousness, materialism, humor, pleasantness and conformity.
A person's morality was measured with phrenology, as well as a sense of justice, kindness and hopefulness. People's spirituality was also under examination, including the extent of their devotion and the focus of their worship.
Perceptual abilities were scrutinized, such as abilities to observe, estimate measurements and discriminate colors. Phrenology also investigated one's reasoning skills in several areas, including cause and effect, mathematics, classification systems and human nature.
Ability and interest in the arts were also supposedly read through phrenology. These included a feel for time, a love of music, an interest in history and a knack for speaking and writing.