My ex did that all the time, unfortuneatly I was not aware of it, even as he told me once 'I like to get reactions from people and I'll do things deliberately just to see how they'll react'....I thought it was more a kind of manipulation, and to a point it was....but eventually, I realized it was also his way to gauge his emotional responses. He would then parrot them back depending on the situation.

It makes me sad for him now, at the time I thought he was mean as hell. He could be, of course, but nothing was done without a reason, even if he couldn't articulate it, nor even consciously see he was doing it.