A psychological device used to protect the ego; a defense mechanism, such as compensation or rationalization.Defense mechanism is the more widely used term, but some theorists, such as H. S. Sullivan, prefer dynamism because it stresses the idea of active forces bringing about changes in our adaptive behavior, and mechanism seems to imply automatic, machinelike reactions. Many other terms are also used, such as adjustment devices, ego defense reactions, defense processes or strategies, behavior mechanisms, and coping mechanisms. The distinctions among these terms are largely on a verbal level, since they refer to the same types of reaction. They all denote techniques which people use in attempting to maintain their emotional security and self-esteem when confronted with difficulties which threaten their ego and arouse anxiety.These patterns are acquired early in life as a means of coping with frustrations and conflicts, and are considered essentially normal and even necessary for personal adjustment. Some are more effective and some are more socially acceptable than others, but all of them tend to become important components of the personality and not just transient expedients. As Thorpe, Katz and Lewis (1961) remind us, “Since they are dynamic in nature, they may become habitual and persist long after the original threats have been removed or overcome.” And since they are so closely involved in adjustment and are such an integral part of the self, any full description of an individual’s personality should include the dynamisms—or mechanisms—he characteristically utilizes.