Researchers say that those who feel powerful at work tend not to smile back at important people and instead save their smiles for those below them in the pecking order.
"Our interpretation of this is that when you are feeling powerful and see a low-status person, you are almost throwing them a bone, thinking "Oh, I should smile at this person because I'm better than them"," the Daily Mail quoted Evan Carr from the University of California as saying.
It is well known that we tend to mimic other people's body language, but in the study Carr wanted to see how we copy facial expressions and whether power and status are important.
For the study, he asked 55 young men and women to write about a time when they felt powerful or powerless.
They were then hooked up to equipment that measures the activity of key facial muscles, and were asked to watch short video clips of people with jobs with different levels of prestige, who were smiling or frowning at them.
As they watched, the equipment measured the activity of the zygomaticus major - the 'smiling muscle' that raises the corner of the mouth.
It also gave readouts for the corrugator supercilii, the 'frowning muscle' that furrows the brow and is frozen by Botox.
The results showed that the volunteers were more likely to scowl in response to a frown from a doctor or someone in a position of power and these frowns were also more intense.
But it was the volunteers' responses to smiling faces that were really telling.
The men and women who felt powerful tended not to smile back at high-fliers but they did return the smiles of those who were lower down the pecking order and their smiles were bigger.
Meanwhile, those who felt powerless smiled at everyone, regardless of their rank.
The researchers think that people who feel powerful try to exert their dominance by not appearing too friendly to those who might be a threat. They have no such qualms about appearing approachable to those who lack authority.
The findings of the study were presented at the Society for Neuroscience's annual conference in New Orleans.