Why does one person respond in a different manner than another in the same exact situation or scenario? The answer is rooted in the individual. The word “individual” describes a person who is distinct from others in a group (Merriam Webster Dictionary, 2011). What differentiates us as individuals are our physical attributes, traits, characteristics, motivations, drives, and experiences, all of which are explained through different dispositional theories. Allport’s Psychology of the Individual theory, believes each person is unique and to understand an individual, it is important to understand the whole person, physiologically and psychologically as he or she grows and changes throughout life. The Trait and Factor theory assumes that personality can be measured by using a combination of testing, observation, and opinions of individuals (Feist & Feist, 2009). Psychology of the Individual theory and the Trait and Factor theory each influence the study of individual personalities with strengths and limitations through their evaluation of the individual and his or her interpersonal relationships.