Final answer:
Reaction formation is a defense mechanism where a person unconsciously exhibits the opposite behavior to their true feelings to protect themselves from anxiety.
Step-by-step explanation:
The psychological defense mechanism described in the question is called reaction formation. This mechanism involves an individual expressing thoughts, feelings, and behaviors that are the direct opposite of their true desires or impulses. It is a way to protect oneself from the anxiety associated with acknowledging these undesirable thoughts or behaviors. When someone uses reaction formation, they may not even be aware that they are acting in contradiction to their true feelings, as these mechanisms operate unconsciously to defend the ego and maintain a self-perception that avoids internal conflict.