a bright child dose poor work in school because she has low “motivation.” A kindergarten teacher may hesitate to criticize a lazy child because it may injure the student’s “self – esteem.” But what is motivation, and how do we know that it is low ? Do we read the child the child’s motivation meter? What about self-esteem? How do we recognize poor self esteem or healthy self- esteem when we cannot see it in the first place? Many research variables, particularly variables of interest to behavioral scientists, are in fact hypothetical entities created from theory and speculation. Such variables are called constructs, or hypothetical constructs.