A: I developed this brief enneagram test as an amusement and to make a point. I have a PhD in psychology (most enneagram therapists do not), and I have extensive training in clinical psychology, psychological test design and test interpretation. The enneagram test seemed to me ripe for a debunking demonstration.

Q: OK, so what is your point?

A: There are many kinds of psychological tests, called performance tests, that measure mental aptitudes or acquired knowledge.

Other tests, called diagnostic tests, ask you questions much as a doctor would — do you sleep well? do you torment your cat? — and use your answers to diagnose specific treatable problems.

Then there is another very large group of tests that might be called descriptive preference tests. These measure no aptitude and frame no diagnosis. They simply ask a person what they like or don't like, or how they like to describe themselves to other people. All enneagram tests are of this type.

Q: So what's wrong with those kinds of tests?

A: The fundamental problem is that the enneagram test does not measure anything that affects any life outcome, so it's essentially impossible to determine the validity of the test — that is, to say if they are worth anything.

For example, an arithmetic test can be used to identify students that might do well or do poorly in an advanced or simplified algebra class. This means that we can compare the test results with the final algebra grades, to see if we should bother using the test again as an educational selection tool. It also means that the test is measuring something real. Or, we can use a diagnostic test to identify patients that might or might not benefit from a certain kind of treatment, then look at treatment outcomes to see if they are better than random assignment to treatment groups. It also means that the test is measuring something real. Either way, there is an explicit, factual way to find out if the test is worth using.

I guess someone could do that with an enneagram test — for example, use the enneagram to predict job satisfaction or marital compatibility or treatment outcomes — but to my knowledge there is no research of any kind to support the occupational or clinical validity of any enneagram test or enneagram classification. That means we have no idea if the test is measuring anything real. In other words, enneagram therapists use the test, but they don't really know if it is worth anything ... with all that implies about their professional ethics.

Q: Then why do therapists use the enneagram test?

A: Three reasons. A minor reason is that the test is part of a persuasion campaign — to assure you that the therapist is wiser than you, has arcane knowledge and extraordinary insight. This power imbalance is always implicit in therapy, even when the therapist disavows it.

A more important reason is that the enneagram test is a standardized set of nine scripts or characters — the romantic, the leader, the helper — that you get to select yourself when you take the test. The type serves as a role or costume that you adopt during therapy. You find your chosen role gratifying to play, and the therapist finds it easy to shape his or her service to nurture the established psychodrama.

I think the main reason is simply that the test fits you into a conceptual box that the therapist is comfortable using in the interpretation of your existential plight. Each type is familiar to the therapist and buttresses claims the therapist will make about you. As I said, the fundamental purpose of these tactics is to make the therapist's job easier, and if that means a less than satisfactory therapeutic experience for you, well ... too bad for you.

Q: Yes, but there are enneagram tests out there with a hundred or more questions! Isn't it stupid to try to do the same thing with just a few questions?

A: No, not at all. The number of questions by itself is no measure of the worth of a test; the Census Bureau uses only one question to assess your your marital status, and that works very well. This is because nearly everyone is very clear about what the question means and how they should answer it, and that they risk nothing by being honest.

One measure of test accuracy is that all the test questions that measure an attribute are highly correlated with each other. Unfortunately it turns out that much of this consistency in descriptive preference tests lies in our language, not in ourselves. This part of psychological test research, called the trait language domain, is very well understood. We know which self descriptive words are consistent with each other; enneagram therapists just string together related words in a single type narrative. This makes the types easy to understand, because all the descriptive words in the alternative are highly correlated.

I examined different enneagram test questions and type descriptions, compared these to what is known from a century of research into human personality, and summarized the types as highly contrasted alternatives. My test is much quicker than any other enneagram test and, based on my experience administering it to a sample of willing enneagram converts, is quite accurate at classifying you into your "true" enneagram type (as defined by any other enneagram test).

Of course, this is tongue in cheek — for a test to measure something there must be something there to measure. The enneagram "types" are language fictions and not actual psychological syndromes. There are dozens of enneagram tests out there, and half educated therapists are making up new ones at the rate of one a month. There is nothing there to measure, except the stories that have already been fabricated for each type.

Q: But why make the type descriptions so negative?

A: People go to therapy for a handful of reasons: interpersonal arbitration (as in marriage counseling), training or teaching (learning how to control anger or be a better parent), drug administration (gotta have that Prozac), adult to adult emotional support, and social recreation — savoring one's personal drama and the shabby triumph of willful dishonesty.

There is absolutely no research evidence that any currently available enneagram test is relevant to any of those therapeutic objectives, except perhaps the social recreation.

Therapists who use the enneagram test usually will steer you towards the social recreation payoffs of therapy — "spiritual growth," "personal development" — because the test can't be used for anything else. The negative type description just takes the fun out of it. And when the fun is gone, you may see the true value of therapies and therapists who are in the business of social recreation.