In 1921, psychologist Carl Jung changed the fundamentals of his field. From his theories on psychological types, the Myers-Briggs Type Indicator was born. To this day, psychologists distribute the psychometric test to patients, hoping to accurately boil down the psychological types of humans into 16 major categories.
Still in use today, the metrics determine whether test takers tend toward certain character traits, such as introversion (I) vs. extroversion (E) or thinking (T) vs. feeling (F). Once taken, test results produce an acronym per individual. For example, “ISTJ” is for an Introvert-Sensing-Thinking-Judging person.