As soon as he's seen Jack out the door, the Doctor is back to being all smiles again. He interpreted Mary's reluctance as the understandable concern about letting someone into their mind with telepathy. It's not exactly an easy thing he was offering, and something the other Time Lords would have frowned upon.

But this one of Jack's compatriots approaches now. "Yes! Of course! I..." he falters, "don't believe I got your name?"

He is, of course, keeping an eye on Duster, but this regeneration is so full of energy, shyness is one trait that has trouble around him.