Eysenck can refer to several synonyms that pertain to the work and contributions of psychologist Hans Eysenck. One such synonym is "personality theory," as Eysenck was known for his contributions in this field. Another synonym is "behaviorism," as Eysenck subscribed to this philosophical approach to studying behavior. Additionally, "intelligence research" can be a synonym for Eysenck, given his work on intelligence testing. Finally, "psychometrics" can also be used as a synonym, as Eysenck developed several psychological measurement tools, such as the Eysenck Personality Questionnaire.