thinks his girlfriend is the "most talented" actress he has ever met.
The 'Wall Street: Money Never Sleeps' star is cautious to speak about new lover Carey Mulligan
- who he stars with in the financial drama sequel - but is astonished by her professional ability.
He said: "I never really had anything in my life that was off-limits but with this, just out of respect, I just don't want to f**k around.
"She's an unbelievably thought-provoking actress, the most talented actress I've ever met in my life, by leaps and bounds.
"Neither one of us are fame whores. It works out. It's not like we're the premiere couple; we're not the red carpet king and queen."
While he is staying quiet about his personal life, Shia was much more forthcoming about his car accident in July 2008 - for which he was arrested for driving under the influence (DUI) but never charged - admitting he is still "angry" about the crash, which resulted in his left hand being permanently damaged.
He added to America's GQ magazine: "I'd be watching the news, and they'd play my car crash, and every once in a while Kim Kardashian's sister would jump on TV and preach to me from the red carpet about how to live my f***ing life.
"And I'm so upset, man. I'm so angry. Because this accident was not caused by me. I got hit. I had a green. This f***er ran a red light. And he flipped my truck, and he shovelled it on my hand. And my fingers are in the street. they're off, they're under the truck door, man.
"This is fake, dude. This is hip bone and the skin that was left over."