The Big 5 model

One personality model survived the 20th century. It's called the Big 5 Personality Traits (5-Factor Model). It was developed in 1961 and since have been developed into its modern form.

The Big 5 model takes a holistic approach by compiling every word that could be considered a personality trait and creating simple questions about them. Based on how people answered initial surveys, researchers used statistical methods to group traits that seemed to go together.