site map 

Philosophy 52: Introduction to Logic

Instructor:  J. Aaron Daniel

     Did your horoscope seem accurate?

     It probably did because it does to most people, especially to most American college students, but there is a trick.

     The trick is that the personality profile that you just read was not written specifically for you.  The exact same profile is generated for everyone who enters their personal information on the astrology page. 

     So this is a single personality profile that seems to fit almost everyone.  In fact the exact horoscope that you just read has been given to lots of people who thought it had been made specifically for them and most of them have thought that it was an excellent description of themselves.  Actually, the average score given to the horoscope that you just read is between 4.0 and 4.5 (on that scale of 0 to 5) even though it is a generic description.

Why Astrology Horoscopes Seem Valid

    So what is it about such descriptions and about us as humans that make these descriptions of us seem so accurate?

     There are three factors that typically account for such seeming accuracy:

Vagueness and Generality

     Many of the elements of both the personality profiles and the predictions of the future that are provided by astrology (as well as fortune-telling, palm reading, graphology, tarot card readings, and psychics) are often so general or so vague that they could mean almost anything or apply to almost anyone.   A word, phrase, or statement is vague if it does not have a clear and exact meaning so that there are borderline areas in which it is unclear if it applies.  A declarative statement or description is general if it can or does apply multiple individuals, objects or situations. Take, for example, the following statements from the personality profile that you just read that was made "especially for you" that "represents your unique picture based on the date, time and place of your birth":

     And what goes for descriptions and personality profiles goes even more so for predictions of the future. The more general and the more vague the prediction, the easier it is for it to seem like it has come true.  Consider these examples taken from the horoscopes in a local paper:

     So vague or general statements often occur within the profiles or predictions that are supposedly generated by astrology and other means of divination, but why do people so often think that such vague or general statements are specifically about particular aspects of their own lives?  This is where the Forer effect and confirmation bias come into play.

back to top of page

The Forer Effect

     The phenomenon of believing that a general personality description is unique to oneself is known as the Forer effect.  The effect is named after psychologist Bertram R. Forer who, in 1948, gave his students a personality test and presented them each with identical analyses copied from a newspaper astrology column.  When asked to evaluate the description on a scale of zero to 5, with 5 being the most accurate, the average score was a 4.26.  The test has often been repeated with similar results.  I've been doing the same thing with with my own Logic and Critical Thinking classes for several semesters with the profile you just read and have consistently gotten the same result. 

     The effect is also known as the Barnum effect (named for P. T. Barnum of circus fame who was extremely good at getting people to believe what he wanted them to) and as the subjective validation or personal validation effect.  What psychologists think is happening is that all people have a desire to liked and respected or validated.   So they tend to accept claims about themselves not in relation to how well they match up with objective empirical evidence, but, rather, in relation to how well they match up with their own personal, subjective desires.  So, those parts of generic personality descriptions that portray us in a good and positive way, those descriptions that match how we hope we are or how we would like to be are the parts that we often focus on and accept as true.  And it is because of these positive descriptions that the generic descriptions of horoscopes, fortune telling and even the personality tests in professional psychology are so well received and so strongly believed to be descriptive of ourselves.

     Consider the following examples from the profile on the previous page.  Notice how many of them are positive or even flattering statements.

     Now honestly think about your own response to these statements when you first read them and still thought they had been created specifically for you.  Didn't you think (or, at least, hope) that they were true of you?  And didn't thinking that others (namely the person who wrote the personality profile) thought that these things were true of you make you feel good about yourself?  It is this need and desire to be liked and well thought of by others that seems to play some significant role in the acceptance of generic profiles as being uniquely descriptive of ourselves.  And a mix of hope, vanity, and wishful thinking lead us to take such descriptions as true and thus subjectively validate ourselves.

back to top of page

Confirmation Bias

     The third component that seems to play a role in people's accepting vague or general descriptions as being specific and accurate descriptions is known as confirmation bias.  Confirmation bias is the human tendency to look for and recognize only evidence that confirms our own views and to ignore and misinterpret evidence that  conflicts with those views.  A number of different psychological tests have shown that people have a natural tendency to look for, notice, and remember evidence that supports or confirms those hypotheses and theories that they already accept or are favorably inclined to accept.  Tests also show that evidence that goes against a favored hypothesis tends to be more often overlooked, ignored, misremembered, misinterpreted, or forgotten.  This bias can come into play in the case of horoscopes and personality profiles like the one you just received in two ways.

     First, everyone already has a mental picture of themselves - hypothesis, if you will, about who and what they are.  So, as with any other hypothesis, the natural tendency to look for confirming evidence will lead individuals to look for and pay attention to that evidence which supports this hypothesis.  So, in the case of a personality profile that is  generated by means of a procedure that supposedly provides unique insight into who a person really is, a person will tend to look first and primarily at those parts of the profile that support the picture that they already have of themselves.  It is these parts of the profile, the ones that match who a person thinks or hopes (see the information on the Forer effect above) he or she is, that confirm his or her self-image and thus are taken as evidence for the accuracy of the profile in question.  Those parts of the profile that conflict with a person's hypothesis of who they are and what they are like tend to be overlooked, ignored or forgotten and so are not taken into consideration when judging the accuracy of the profile as a whole.

     The second way that confirmation bias can affect how accurate and valid a personality profile seems comes from the individual's preconceived notions about the legitimacy or illegitimacy of astrology (or fortune telling or psychics or graphology or psychological testing).  If an individual approaches a personality profile that was supposedly generated specifically for her using a method that she already believes or hypothesizes is a legitimate and accurate way of divining one's personality, then she will tend to notice and give weight to only those parts of the profile that seem accurate and thus serve to confirm the legitimacy and accuracy of that method.  If you believe in astrology, then you will notice only those parts of your horoscope that seem accurate and thus are evidence that confirms astrology.  And since the people that read horoscopes, have their palms read, and call psychics tend to be those that already think that there must be something to such supernatural or paranormal ways of learning about the world, they tend to focus on those parts of their readings that confirm their belief in such methods.

    So when taken altogether, the vagueness and generality of the descriptions used in the profiles provided by astrology, the Forer effect, and confirmation bias have a tendency to make the generic descriptions (especially the positive ones) seem as though they accurately and specifically describe the individual person for whom it was supposedly generated.

back to top of page

How to Think Critically and Objectively About Personality Profiles

    The trick to objectively thinking about and judging the accuracy and legitimacy of methods of generating personality profiles such as astrology is to be aware of these tendencies and biases and take extra effort to compensate for them.  This means giving more weight to descriptions and predictions that are highly specific than to those that are vague and general.  It also means being aware of how much we each want to be thought well of by ourselves and others and to not give more weight to the positive descriptions of ourselves than we do to the neutral or negative descriptions.  And, finally, it means making an effort to look for disconfirming evidence as well as confirming evidence when evaluating a claim.  A good way to do this is to keep a number of different alternative hypotheses in mind when evaluating a claim that something is or is not the case.

More on Skepticism and Critical Thinking

     Thinking carefully and objectively about the world is important and often involves critical thinking and skepticism.  The following links will take you to sites about the Forer effect, confirmation bias, skepticism and critical thinking.

Back to the Intro to Logic (WS04) Homepage