infantilism
noun /ɪnˈfæntɪlɪzəm/
/ɪnˈfæntɪlɪzəm/
[uncountable]- (disapproving) silly behaviour that is typical of a child and not suitable in an adult
- the trivial infantilism of commercial movies
- (psychology) the fact of adults continuing to behave like children, in a way that is not normal