By Dr. Samuel Barondes, author of Making Sense of People

When we meet someone new, we immediately form a tentative picture of his or her personality.  We generate this first impression in a matter of seconds, because we need it to guide our initial give and take.

Our amazing ability to rapidly size people up works so well that we continue to rely on it as we get to know the person better.  In doing so, we keep building a more elaborate intuitive impression—an impression that we rarely bother to consciously examine.  Although we may spend hours methodically assessing a new smartphone before deciding what we think of it, our assessment of someone’s personality keeps being made by the seat of our pants.

There are times, though, when we want to consciously think over what we’ve observed.  We may, for example, want to figure out if a person we are dating has the right stuff for a permanent relationship by discussing it with our friends.  But these conversations are often uninformative because few of us have been taught a systematic way to assess personalities.  This limits our ability to come up with a thoughtful appraisal of the person we have in mind, even with the assistance of those who are eager to help us.

I have a system for going beyond a first impression by consciously assessing the personality of someone who interests you.  With this system, you and your friends can discuss the many observations you’ve made, and come up with a clearer and more useful picture.  It begins by showing you how to thoughtfully assess basic characteristics such as sociability, warmth, competence and emotional stability.  This will help you decide how much it matters to you that the person is shy or outgoing, warm or cold, reliable or unreliable, and content or easily upset.

You will then be ready to look for signs of troublesome patterns such as compulsiveness, narcissism, sociopathy and paranoia, and to consider how this might affect you.  Having clarified these matters will put you into a position to make a moral appraisal of the person’s character, using your own personal standards.  You’ll also learn how to put this all together with what you know about the person’s view of who he or she really is, a sense of identity that includes goals, ideals, and a life plan.

Making sense of someone in this systematic way will help you decide how compatible the two of you are. Although a first impression tells you if you want to get to know someone better, a thoughtful appraisal may reveal both admirable and dangerous aspects of a personality that you might have overlooked, and that may prove to be important in the long run.

Samuel Barondes is the Jeanne and Sanford Robertson Professor and Director of the Center for Neurobiology and Psychiatry at the University of California, San Francisco. A leading psychiatrist and neuroscientist, he is a member of the Institute of Medicine and the American Academy of Arts and Sciences.  His books include Mood Genes, Better than Prozac, and the Scientific American Library title Molecules and Mental Illness. He lives in the San Francisco Bay area.