I recently came across this series on Transactional Analysis, a theory of personality developed in the 1950s by Eric Berne. This theory attempts to explain how we are structured psychologically through the ego-state or Parent-Adult-Child (PAC) model. This model helps explain how we function and express our personality through our behavior and communication.
When in the Parent state, a person will "behave, feel, and think in response to an unconscious mimicking of how their parents (or other parental figures) acted, or how they interpreted their parent's actions. For example, a person may shout at someone out of frustration because they learned from an influential figure in childhood the lesson that this seemed to be a way of relating that worked." (source)
The Adult state "is most like a computer processing information and making predictions absent of major emotions that could affect its operation. Learning to strengthen the Adult is a goal of TA. While a person is in the Adult ego state, he/she is directed towards an objective appraisal of reality." (source)
Finally, when in the Child state, a person will "behave, feel and think similarly to how they did in childhood. For example, a person who receives a poor evaluation at work may respond by looking at the floor, and crying or pouting, as they used to when scolded as a child. Conversely, a person who receives a good evaluation may respond with a broad smile and a joyful gesture of thanks. The Child is the source of emotions, creation, recreation, spontaneity and intimacy." (source)
Watch the video to learn more about these ego states and how they impact the way we respond, think, and communicate.