Regression

Description:
Regression involves taking the position of a child in some problematic situation, rather than acting in a more adult way. This is usually in response to stressful situations, with greater levels of stress potentially leading to more overt regressive acts.

Regressive behavior can be simple and harmless, such as a person who is sucking a pen (as a Freudian regression to oral fixation), or may be more dysfunctional, such as crying or using petulant arguments..

Link:
ChangingMinds.org