But most people don't actually believe in this stuff, right? While astrology has repeatedly failed to predict even basic personality traits like introversion, people may be incorporating its ideas into their long-term self-image, according to a study by Margaret Hamilton, a psychology professor at the University of Wisconsin, in Washington County. In the journal of Personality and Individual Differences, she shows that a sun sign's favorability may determine how readily people come to believe it describes them.
Once considered an exact science, a person's sun or star sign is determined by the position of the sun in relation to the stars at the time of their birth. The 12 sun signs roughly correspond with the 12 months of the year, with odd numbered signs associated with months such as February and April, and positive numbered signs with months such as January and March.
Hamilton showed that, of the 12 signs in the zodiac, subjects rate characteristics attributed to the negative numbered signs—such as Aquarius and Aries—as more socially desirable than the positive numbered signs—such as Capricorn and Pisces. In a separate study, she found that subjects with negative sun signs are more likely to believe in astrology than subjects with positive sun signs. This shows that people may more likely to believe in astrology if their sign's characteristics are favorable.
So, are Sagittarians more likely to travel because they know their sun sign points to adventure? And are Aquarians more likely to be eccentric because they think they have an excuse to be oddballs?
More likely, they will pick out examples in their lives that match these preconceived ideas. Most people like to travel occasionally and everyone has her own eccentricities, but if it's written in the stars it's easy to point to astrology as "the reason." It can also be a way to avoid responsibility for flaws we'd like to ignore: "Of course I'm financially unstable—we Sagittarians are notoriously irresponsible."
Believing is key. In a classroom demonstration described in Teaching of Psychology, researchers used student responses to show the affects of "expectancy confirmation"—the tendency to look for confirmation of previously held beliefs. They gave students a list of horoscope predictions from the previous day and asked them to pick the one that was most accurate for them. Half of the surveys included the corresponding star sign for each prediction and half did not. In the end, students were more likely to rate their own horoscope as most accurate when they knew which one was supposed to pertain to them.
Astrology doesn't just affect "believers." Most of the subjects in Hamilton's study had only garden-variety knowledge of astrology, and she did not remind them about their sun sign characteristics. Yet, even without prompting, they still answered consistently along negative or positive lines—subjects with more desirable sun signs showed a stronger belief in sun sign validity than subjects with less desirable signs. It goes to show you that people readily integrate such predictions into their long-term self-concepts. I guess if we like what we see, we might not be able to resist believing.