I think the philosophical answer here is that it’s our beliefs, commitments and values that lend our actions consistency. If the image we present to the world is at odds with our core commitments, then that mismatch will tend to be betrayed in small ways. There’s an old truism that you can tell a lot about a person by the way he or she treats the waiters and waitresses in a restaurant. So my advice would be this. Watch the person carefully, not in terms of how he or she behaves towards you, but towards others. Is he or she kind or rude to service personnel, children, animals, significant others, parents, acquaintances and so forth? How does he or she react under pressure or when uncomfortable? Have you met family members, close friends, employees or so forth, and if so, what did they say about the person?

In addition, pay close attention to what that person says about others. Who does he or she admire, who does he or she despise? Both the traits that the person admires, and (paradoxically) the traits he or she finds particularly bothersome are clues as to the secret personality beneath the façade.

In my opinion how someone treats other people is the most important question, but there are other clues available as well. What does his or her home or workspace look like? How does he or she respond to tasks? To criticism? To praise? To gifts? To disappointments?

In sum, I would say that most people are constantly broadcasting who they really are, even if they have an image that is quite different. The key is to be observant enough to see the real person beneath, and to resist the urge to fool oneself into believing that someone is better –or worse! –than he or she really is.