Daily Archives: March 5, 2011

Astrology, the Forer Effect, and the Allure of Personal Feedback

By: Christopher C. Duke, Ph.D.

You may have heard some of the recent discussions that the astrological zodiac is actually astronomically inaccurate. Because of shifts in the earth’s axis called precession, similar to how a spinning top wobbles, the traditional zodiac has been drifting out of its original alignment for hundreds of years. That means that old zodiac signs have shifted in date and a new 13th constellation, Ophiuchus, could also be included in the zodiac. Thus, even if you buy into the idea that stars can influence your fate, astrologers have focused on the “wrong” stars for many hundreds of years. Now, hopefully most readers know that astrology is limited to, if we are being generous, “entertainment value” only (see Carlson, 1985 if you need empirical convincing). However, millions of people take astrology seriously, and that makes its appeal a topic of legitimate psychological investigation. So, why do so many people believe that horoscopes provide insight into their lives?

One answer is the Forer Effect, which is a cognitive bias where people are likely to interpret statements or predictions as being personally relevant. However, these statements can apply to nearly anybody. In a 1948 study, psychologist Bertram Forer gave participants a “unique personality analysis” and asked them to rate its accuracy from 1 to 5. The “unique personality analysis” was always the same, but had an average accuracy rating of 4.26. This was the statement:

You have a need for other people to like and admire you, and yet you tend to be critical of yourself. While you have some personality weaknesses you are generally able to compensate for them. You have considerable unused capacity that you have not turned to your advantage. Disciplined and self-controlled on the outside, you tend to be worrisome and insecure on the inside. At times you have serious doubts as to whether you have made the right decision or done the right thing. You prefer a certain amount of change and variety and become dissatisfied when hemmed in by restrictions and limitations. You also pride yourself as an independent thinker; and do not accept others’ statements without satisfactory proof. But you have found it unwise to be too frank in revealing yourself to others. At times you are extroverted, affable, and sociable, while at other times you are introverted, wary, and reserved. Some of your aspirations tend to be rather unrealistic. Security is one of your major goals in life.

The “analysis” above was simply a combination of sentences from several different horoscopes. The effect has been duplicated by other researchers many times, with most people claiming it to be 80% to 90% accurate; it appears nearly any horoscope can apply to nearly any person. One of the tricks to this “accuracy” is to say two statements that appear to be opposites and cover everything in between, eg, “at times you are extroverted, while at other times you are introverted.” A similar trick is to say something that is true of just about everyone, eg, “you need for other people to like you” or “you have considerable unused capacity.” Finally, these statements tend to flatter our own egos. People tend to find personally relevant information satisfying, particularly when it is complementary, as many of the above statements are, eg, “you are an independent thinker.”

While most of you are already aware of the psychological tactics that make astrology convincing to some people, pop psychology can exploit many of the same cognitive biases. When you hear about a psychological analysis method or personality test, be critical, consider the Forer Effect and ask yourself the following questions: What evidence is there to support the claims? Is the evidence peer-reviewed? Is the promoter selling something? Pop psychology can appear convincing because it often appears to have a veneer of academic rigor, and for this reason we must be especially critical and skeptical when considering psychological theories.

Carlson, S. (1985). A double-blind test of astrology, Nature, 318, 419-425.

Dickson, D.H. & Kelly, I.W. (1985). “The ‘Barnum Effect’ in Personality Assessment: A Review of the Literature”. Psychological Reports, 57, 367–382.

Forer, B.R. (1949). “The fallacy of personal validation: A classroom demonstration of gullibility”. Journal of Abnormal and Social Psychology, 44, 118–123.