TRANSACTIONAL ANALYSIS
Taken from Dr. Eric Berne, MD.

What this theory says is that, every person comprises three sub- personalities:

Parent: the remnant of his parents instructing him/ her over things and morality.
Adult: The rational, logical brain.
Child: Remnants of childhood, the child who likes to have fun and be cared for.

Moreover, if someone is talking to you, you should be able to gauge what part of the person is making the statement, and to which part is it addressed.
If you reply from the same sub- personality as the speaker intends you to, you get a normal transaction (talk).
But if you reply from a different sub- personality, you cross the transaction, and create conflict.
e.g.:
You: I have misplaced the keys. Have you seen them? (intended as A-----A, adult to adult conversation)
Me: Why cant you take care of your stuff. You are so irresponsible. (P----C, parent to child conversation)

explanation: 'You' just asked me a question (A----A), and expected an (A----A) reply. But when I hear you make that statement, for whatever reason, I take it as (C----P), a child asking a parent, and I reply along the same path (P-----C).

This is a crossed transaction, the paths of (A----A) and (P-----C) intersect, and such a conversation is bound to raise conflict.

So try to spot what your friend, spouse, etc... is trying to tell you, and answer along the same path. Else you will create conflict.