Gordon Allport developed one of the earliest theories of personality traits. He focused on the uniqueness of each individual and how their traits are shaped by present contexts rather than past history. Allport identified three levels of traits: cardinal traits that dominate a person's behavior, central traits that describe basic characteristics found in most people, and secondary traits that only appear in certain situations. Allport developed a list of over 4,500 trait words and believed traits could be observed and used to distinguish individuals' personalities.