Final answer:
Regression is a defense mechanism where individuals revert to earlier, often less mature behavior patterns when facing stress. It is intended to manage anxiety and provide emotional comfort.
Step-by-step explanation:
The term regression is used to describe the phenomenon of turning back to former behavior patterns in time of stress. This defense mechanism, identified by Sigmund Freud, suggests that individuals may revert to patterns of behavior previously exhibited at an earlier stage of development when faced with uncomfortable situations or emotional challenges. For example, an adult may start thumb-sucking or a toilet-trained child may begin to wet the bed again when undergoing stress. Such regressions are understood as attempts to manage anxiety and gain psychological comfort, albeit in a way that might not be socially appropriate or effective in the long-term.