What’s My Team Member Style? is based on the well-known research and personality theories of psychologists Carl Jung, William Moulton Marston, and others. Most research has identified two basic dimensions of style, which we refer to as assertiveness and expressiveness. Assertiveness is the effort a person makes to influence or control the thoughts or actions of others. Expressiveness is the effort that a person makes to control his or her emotions and feelings when relating to others.