It is apparently in contrast with how she previously interacted with David Tennant, says the actress, who previously appeared as Professor River Song in the 2008 episodes Silence in the Library/Forest of the Dead, both by current showrunner Steven Moffat
“I loved working with David Tennant but the relationship was very different to the relationship that Matt and I are creating,” she said. “Because David was already coming to the end of his incarnation as Doctor Who and he was a little bit more suspicious of River Song.
“Whereas with Matt, the Doctor almost knows who I am because of the episodes before that David did. He has that memory still and he has that memory of River Song dying before his eyes.”