That kind of ties in with what I mean.

Small children will often save up their 'childish and needy' feelings for the person/ people they feel safe with, who they feel secure enough to be vulnerable with. So a four year old might be all mature and poised at school (well, relatively!) then come home and throw a tantrum or be clingy with mummy to decompress after the hard work of being on their best behaviour at school all day. They know mummy (or whoever) will not reject them.