[dorkwood]

I think there's a logical explanation for why being born at a particular time of year might have an effect on how your personality develops, and that's that the time of year you're born determines where you are placed within your cohort at school. Only just old enough for this year's intake? You're more likely to be shorter and weaker than everyone else on the sports team. Almost too old, but just squeaked in? You have both a physical and mental advantage over everyone else.

While 'horoscopes' might not have any basis in reality, it's not unimaginable to me that groups of personalities might arise who all share a particular birth month.

[jkhdigital]

In general I agree with you, but the more I consider topics like this the more I see it as a problem of correlation strength vs. effect size. That is, at the population level there may very well be a strong correlation between birthday and certain personality traits, but the effect size is likely to be infinitesimal compared to everything else we know about what shapes a person’s psychology.

I actually think this is one of the ways that published science tends to distort rather than clarify our view of reality, as the strength of correlation tends to be overly emphasized as measure of quality or relevance.

[marshallbananas]

That's most definitely true. But describing one's character or predicting behavior based on that is simply random stereotyping. And even if we could make some use of it, the astrology crowd would never embrace it.

[api]

That's exactly the sort of thought I've always had about astrology: if there's any truth at all to it, it's because all the astrology BS is just being used as a clock. The effect is the result of other factors that are periodic such as seasons, social factors as you say, etc.

[maccolgan]

Any such effect would be infinitesmally small at a city, state or nation level, not to mention such effects will not be self-repeating, defeating the purpose of such a book