This exercise explores four important logical fallacies that help explain why people enjoy pseudo personality tests and horoscopes.

Begin the exercise.

Read This Horoscope:

Does this horoscope describe your personality? Most of you will find some thing or things in this horoscope that you can relate to. But this horoscope is totally bogus, just like many of the "Personality Tests" that you can find on the Internet. (Remember: Only personality tests given by a psychologist are valid measures of personality.) When you read your horoscope, or when you take a "Pseudo" personality test in a magazine or on the Internet, try to find within the test examples of the following logical fallacies:


The first reason we often accept horoscopes and "pseudo" personality descriptions is that we think they are accurate, when they are actually just ambiguous, broad statements that fit just about anyone. The fact that we are so readily disposed to accept such generalizations is known as the Barnum Effect after P. T. Barnum, the legendary circus promoter who said, "Always have a little something for everyone" and "There's a sucker born every minute." Read the horoscope again and identify the general and ambiguous statements that qualify as the "Barnum Effect."

Return to the horoscope.


According to the fallacy of positive instances, we tend to notice and remember events that confirm our expectations, and ignore those that are nonconfirming. Therefore, if you believe some of what a horoscope or pseudo-personality test says about you, then you will tend to ignore those results with which you do not agree. Take another look at the horoscope at the beginning of the exercise and try to notice how many statements apply to you and how many do not. People tend to remember only the positive, not the negative in these types of statements.

Return to the horoscope.


The self-serving bias refers to our tendency to prefer information that is flattering. Most nonscientific, bogus "personality tests" are composed of flattering or neutral characteristics. In fact, research shows that the more favorable a personality descritption, the more people believe it, and the more likely they are to believe it is unique to themselves (Guastello et al., 1989). (This reference can be found in Psychology in Action, 4e.) This is one of the reasons why people prefer "pseudo" tests to real, valid personality tests--the "pseudo" tests are generally more flattering. Go back to the horoscope and evaluate its general overall tone. Are the descriptions generally flattering or negative? See how many examples of the self-serving bias you can find in the horoscope.

Return to the horoscope.


Think back to the horoscope at the beginning of this exercise. Did you make excuses for the parts of the horoscope that did not fit you? Ad hoc is Latin for "special purpose" or "after the fact." Thus, when a horoscope or personality description does not exactly fit, it is easy to give an ad hoc explanation--an improvised explanation for the situation at hand. Suppose you are told by an astrologer that you have a strong need for other people to like and admire you. When you object, a "talented" astrologer might offer this ad hoc explanation: "Given your exceptional abilities and people skills, you automatically receive liking and admiration from others. Therefore, you don't recognize how much you need approval because you get it all the time." Ad hoc explanations make it impossible to logically refute astrological claims because even when they are wrong, they are right!

Return to the horoscope.

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