"We saw a steeper decline in heart rate and a faster physiological stress recovery when they were smiling, " even though the participants weren't aware they were making facial expressions, says Sarah Pressman, co-author of the study and an assistant psychology professor at University of California, Irvine.

WSJ: Stress-Busting Smiles

Master Chief retains his detached, no-nonsense soldier persona for most of the campaign, but there are moments you want his helmet to come off so you can see the facial expressions you sense he's making.

CNN: Review: 'Halo 4' is franchise's best yet

But hospital authorities told the court that Ms Shanbaug "accepts food in normal course and responds by facial expressions" and responds to "commands intermittently by making sounds".

BBC: India court rejects Aruna Shanbaug euthanasia plea