If you watch the Robin Williams / Oliver Sacks movie/book Awakenings you will see what dopamine can and cannot do to the brain.
Evolution has taught us to read and understand facial expression beyond language or other forms of expression. From a distance you can usually detect friend or foe. The stranger may be carrying a weapon, but their eyes reveal all.
I suspect part of this is the damage inflicted on doctors in medical school where we are taught to be vigilant, to utilise our Sherlock.