When a young person will not go in, social fear is the most common thing underneath. Start there, before anyone reaches for words like lazy or defiant.

What the research says

A systematic review of emotion regulation found that people with social anxiety and depression tend to use expressive suppression more and reappraisal less, meaning the feeling is being pushed down rather than shown. That is one reason social fear can read from the outside as flatness or stubbornness. The review pools cross-sectional studies, so it describes a general pattern and cannot tell you what any one child is doing.

Strength of evidence: one line of research. A single study, or a theoretical account.