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“If scientists wrote horoscopes, this is what yours would say”

David Hogg points to this excellent science-based news article by Martha Gill. It’s not about astrology at all; rather, Gill alludes to scientific findings correlating different attributes with time-of-year of birth. At least, I assume this is science-based. It’s possible that Gill is just making it all up (or, for that matter, that the author of the article is not named “Martha Gill” at all) but something about the article’s tone makes me think it’s legit.

Hogg writes:

Astrologers say that people born in different seasons have different capabilities and traits. So does statistical scientific research. The only fundamental differences are (a) statistical researchers have better methods, and (b) scientists use different causal models (the models rarely involve Jupiter, for example).

I’d add another difference. Scientists, because of their more reasonable models, have a more reasonable sense of the precision of their claims. Some astrologers will claim the actual date of your birth is relevant, and even the newspaper columns do it by month, but I doubt you’d get that sort of sharp pattern coming from any real effects.

Hogg adds:

Because I come from a profession with its roots in astrology, this is an issue I have been following for a few years. . . . If you think back to when astrology was born, these effects would have been much larger, because the availability of light, heat, and (most importantly) a balanced diet would be a strong function of month, and have a big effect on pregnancies and infants. So the evidence for astrology might have been enormous in the past.

Maybe . . . but people hardly need evidence to believe in things! It’s enough for the stories to be pleasant, I think.

P.S. I have only two complaints about Gill’s article. First, she doesn’t point to any of her sources. That just sucks. Link, please. My second problem—and, yes, I know I’m being picky—is that she gives a different “horoscope” for each month. Really, though, there’s no way these findings are as precise as to be assigned to particular months. I think it would’ve been more reasonable to have just four categories, one for each season. That must be roughly the precision of these results.


  1. Phil says:

    I agree that strong month-to-month effects seem implausible but I could imagine a couple of specific months being important. I think a lot of schools have a cutoff for the age at which kids can start kindergarten or first grade; a kid who barely makes it will be the youngest kid in his class, or one of the youngest, all the way through school (unless he’s held back later). A kid who barely misses it will be the oldest kid in his class, or one of the oldest, all the way through school (unless he skips a grade).

    Most schools start around the same time of the year, so if they also choose similar age cutoffs then all around the country these effects apply to cohorts of kids with the same birth months.

    So I could at least _imagine_ a sharp change from month to month.

  2. Wayne says:

    There is certainly no predictive power to astrology. But I have wondered from time to time if the conditions of your gestation — ambient light levels, heat, your mother’s hormonal levels, etc — might not cause you to be wired slightly differently than if you had matured at a different time. For example, someone born in October in the northern hemisphere would have spent key developmental times in greater heat and light than someone born in April. Heat, or their mother’s body working harder to shed heat, might affect a developing fetus. Light levels can affect the mother — I’m thinking of things like SADD — and can also directly affect the fetus. (I just read a study that claims that cats born to mothers who were kept in the dark the entire pregnancy have certain eye development problems, and that the dim light that penetrates into the womb is important to the kitten’s eyes.) In agrarian societies, the time of year would affect access to certain kinds of foods and hence vitamins. Etc.

    So I would not be totally surprised that people born in the same hemisphere at the same time of year might not be more likely to share certain traits than otherwise. Of course, this has nothing to do with horoscopes, which are simply self-fulfilling prophecies and confirmation bias.

  3. FredR says:

    In his autobiography “Rebel with a Cause” Hans Eysenck talks a fair amount about how there might some truth to astrology.

  4. Agreed that there should be references. If anyone has good references, please post in the comments.

    ps. love the graphic!

  5. konrad says:

    If such effects are mainly due to seasonal changes, they should be larger in countries close to the north pole than in countries slightly north of the equator, and 6 months out of phase in the southern hemisphere. This is very testable. Social factors such as the timing of Christmas may be a confounder.