Emily J. Hangen (with Andrew J. Elliot) is a contributing author, "Achievement Motives."

This Encyclopedia provides a comprehensive overview of individual differences within the domain of personality, with major sub-topics including assessment and research design, taxonomy, biological factors, evolutionary evidence, motivation, cognition and emotion, as well as gender differences, cultural considerations, and personality disorders. It is an up-to-date reference for this increasingly important area and a key resource for those who study intelligence, personality, motivation, aptitude and their variations within members of a group.