It’s human nature to be a psychologist.
We’ve evolved to become a very social species, and because of this we’ve developed what psychologists call empathy or theory of mind. This is our ability to attribute mental states – like thoughts, feelings, and intentions – onto ourselves and others.
If we see someone smile, we assume they are happy. If we see someone crying, we assume they are sad. We are constantly reading into people’s behaviors, body language, and speech to determine what they are really thinking and feeling in any given situation.
Ultimately, this “theory of mind” comes with the understanding that what one person is thinking or feeling can be different than what you are thinking and feeling. We each have different minds.
Psychologists often test for this in children through something called a “False Belief Test.” You can find a video demonstration of it here. By the age of 4-5, most children are are the point in their cognitive development where they can attribute mental states to others (unless they have autism or a mental disorder).
While it’s natural to try to read people’s minds and understand more about their inner workings – to become a type of “folk psychologist” or “armchair psychologist” – this tendency can also get out-of-hand sometimes.