Within our autonomic system there are a lot of functions that are dealing with our unconscious emotions. The heart reacts automatically on fear, so does lungs, and our reaction due to our basis reaction on e.g. fear, stress. But a smile that is not genuine will always be false. To be a true smile your eyes has to sparkle. The true emotions of the soul can t be faked, most of us see through faked emotions.
Disgruntled employees express anger that leads to conflict.
By acknowledging that feeling, you can change the process of anger. If that doesn't work it will result in a behavior that drags everybody down and with a loss of production as a result. So support a corporate culture that is dealing with feelings, and that will be in the long run a good investment. We need very fast reaction automatically. Despite your hard try to hide your emotions, people can see it anyway.