# Birthday-dependence of test scores? **URL:** \ **Category:** Factual Questions\ **Created:** [September 19, 2005, 10:39pm UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438 "2005-09-19T22:39:07Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![yerba\_buena](https://avatars.discourse-cdn.com/v4/letter/y/7ea924/32.png) [@yerba\_buena](https://boards.straightdope.com/u/yerba_buena)\ **Post date:** [September 19, 2005, 10:39pm UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438/1 "2005-09-19T22:39:07Z")
Has anyone ever done studies on whether what month/day of the year you were born is an indicator for how well you perform on test scores or some other measure of success? This sounds a little weird, but allow me to explain my most recent brain fart: for couples who plan well (and may be self-selective for good parents), the distribution of babies born throughout the year is likely not equal - that is, female teachers may choose to time pregnancy so they give birth in June/July and have the summer to recouperate, etc. Likewise, for couples who don’t plan well (and may be self-selective for bad parents), the chances of getting drunk / having unprotected sex on New Year’s Eve and giving birth in September is slightly higher. I’m sure that any difference would be slight, but I would be incredibly interested to know whether subtle behaviors of the parents could lead to significant disparities in their children. ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [September 19, 2005, 10:54pm UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438/2 "2005-09-19T22:54:13Z")
This is only marginally related but [schizophrenia incidence](http://www.schizophrenia.com/prevention/season.html) is related to day of birth. People born in the winter and early spring are more likely to become schizophrenic. Some researchers believe this is due to a virus contracted in early development. The only reason I bring that up is that it is a mental trait influenced by birthday. Birthdays are not randomly distributed but the differences aren’t that large. I couldn’t find anything directly related to your question. ---
**Author:** ![Anne\_Neville](https://avatars.discourse-cdn.com/v4/letter/a/b9e5f3/32.png) [@Anne\_Neville](https://boards.straightdope.com/u/Anne_Neville)\ **Post date:** [September 19, 2005, 11:31pm UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438/3 "2005-09-19T23:31:57Z")
One problem with that theory is that most women don’t work at jobs where they have long periods of vacation. There’s probably also a correlation between older parents and higher test scores (both being more common in higher socioeconomic classes, at least in the US), and a lot of older parents can’t plan births down to the month because of lower fertility. ---
**Author:** ![rayh](https://avatars.discourse-cdn.com/v4/letter/r/e79b87/32.png) [@rayh](https://boards.straightdope.com/u/rayh)\ **Post date:** [September 19, 2005, 11:47pm UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438/4 "2005-09-19T23:47:31Z")
> [@yerba buena](#): > > Has anyone ever done studies on whether what month/day of the year you were born is an indicator for how well you perform on test scores or some other measure of success? > > This sounds a little weird, but allow me to explain my most recent brain fart: for couples who plan well (and may be self-selective for good parents), the distribution of babies born throughout the year is likely not equal - that is, female teachers may choose to time pregnancy so they give birth in June/July and have the summer to recouperate, etc. Likewise, for couples who don’t plan well (and may be self-selective for bad parents), the chances of getting drunk / having unprotected sex on New Year’s Eve and giving birth in September is slightly higher. > > I’m sure that any difference would be slight, but I would be incredibly interested to know whether subtle behaviors of the parents could lead to significant disparities in their children. I would have thought that children born in September would have the advantage as they would be the older ones in the class, those born in June/July/August being the younger ones. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [September 20, 2005, 12:55am UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438/5 "2005-09-20T00:55:56Z")
> [@rayh](#): > > I would have thought that children born in September would have the advantage as they would be the older ones in the class, those born in June/July/August being the younger ones. Which is counteracted by the fact that many regions have cutoff dates for school admission based on age. The children of working couples is often deliberately planned to allow them to enter school at the earliest possible age rather than having to pay for an extra 11 months of daycare/nannies or forfeit an extra 11 months wages. Exactly what effect that will have is hard to judge since dual working couples probably comprise the working poor as well as dual professional couples. On average you’d expect such children to be riased in houselholds with more money and as a result they’d have an advantage. All of which shows just how hard it is to try to fit this sort of hypothesis to the complexities of human life. ---
**Author:** ![RaftPeople](https://avatars.discourse-cdn.com/v4/letter/r/6f9a4e/32.png) [@RaftPeople](https://boards.straightdope.com/u/RaftPeople)\ **Post date:** [September 20, 2005, 1:26am UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438/6 "2005-09-20T01:26:53Z")
> [@rayh](#): > > I would have thought that children born in September would have the advantage as they would be the older ones in the class, those born in June/July/August being the younger ones. Myself, and everyone I know that was born in September was always one of the youngest in class. Maybe cutoff’s are different in different areas, but in the school district I grew up in, it was sometime in Oct or Nov. ---
**Author:** ![ambushed](https://avatars.discourse-cdn.com/v4/letter/a/3bc359/32.png) [@ambushed](https://boards.straightdope.com/u/ambushed)\ **Post date:** [September 26, 2005, 7:12am UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438/7 "2005-09-26T07:12:36Z")
> [@yerba buena](#): > > Has anyone ever done studies on whether what month/day of the year you were born is an indicator for how well you perform on test scores or some other measure of success? Do you realize that you’re essentially asking if astrology is valid? It’s not. [Astrology](http://skepdic.com/astrolgy.html) ---
**Author:** ![Harriet\_the\_Spry](https://avatars.discourse-cdn.com/v4/letter/h/e56c9b/32.png) [@Harriet\_the\_Spry](https://boards.straightdope.com/u/Harriet_the_Spry)\ **Post date:** [September 26, 2005, 11:20am UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438/8 "2005-09-26T11:20:48Z")
I realize that the plural of anecdote isn’t data, but couldn’t resist. Born in September. Oldest in class. Brilliant. 😃 Always attributed this to being a Virgo. 😃😃 But on a more serious note, no, the OP is not testing the validity of astrology. The OPs hypothesis would have August, September October children varying on a continuum. Astrology would hold these children to be Leos, Virgos, and Libras, who do not vary on a continuum but are considered as separate populations with different characteristics. ---
**Author:** ![Shalmanese](https://avatars.discourse-cdn.com/v4/letter/s/45deac/32.png) [@Shalmanese](https://boards.straightdope.com/u/Shalmanese)\ **Post date:** [September 26, 2005, 12:27pm UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438/9 "2005-09-26T12:27:27Z")
Has anyone done a large scale study to detect any sort of correlation between birthdays and anything imaginable? Sort of in the style of the twin studies. It seems like something that is worthwhile doing, if only to prove the negative. ---
**Author:** ![Walton\_Firm](https://avatars.discourse-cdn.com/v4/letter/w/45deac/32.png) [@Walton\_Firm](https://boards.straightdope.com/u/Walton_Firm)\ **Post date:** [September 26, 2005, 4:42pm UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438/10 "2005-09-26T16:42:18Z")
Well, there is the [Mars effect](http://en.wikipedia.org/wiki/Mars_effect), which appears to have _some_ statistical data to back it up, although the effect seems to come and go depending on who does what with which data set. Explanations for the effect range from “astrology is true” to “people who are among the oldest in their class are more likely to become sports stars”, and of course the good old “it’s just a statistical aberration”. > [@ambushed](#): > > Do you realize that you’re essentially asking if astrology is valid? No he’s not. There are several non-supernatural possible explanations for why the season in which you are born might affect some of your biological traits. **Yerba buena** named one possibility (admittedly, a rather far-fetched one) in his OP. I just named another one. Even if the answer to the OP’s question were affirmative, that’s still a _huge_ difference from how an astrologer claims to be able to deduce all kinds of minute details about your character from the exact moment of your birth. ---
**Author:** ![ambushed](https://avatars.discourse-cdn.com/v4/letter/a/3bc359/32.png) [@ambushed](https://boards.straightdope.com/u/ambushed)\ **Post date:** [September 27, 2005, 5:42am UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438/11 "2005-09-27T05:42:36Z")
> [@Harriet the Spry](#): > > But on a more serious note, no, the OP is not testing the validity of astrology. The OPs hypothesis would have August, September October children varying on a continuum. Astrology would hold these children to be Leos, Virgos, and Libras, who do not vary on a continuum but are considered as separate populations with different characteristics. I don’t agree. The premise of astrology is that your birthdate influences your life, particularly one’s success in life. Let me repeat the OP: > [@yerba buena](#): > > Has anyone ever done studies on whether what month/day of the year you were born is an indicator for how well you perform on test scores or some other measure of success? For the record, a great many such studies have been performed. Those who believe in astrology say “yes”, and scientists say “no”. ---
**Author:** ![ambushed](https://avatars.discourse-cdn.com/v4/letter/a/3bc359/32.png) [@ambushed](https://boards.straightdope.com/u/ambushed)\ **Post date:** [September 27, 2005, 5:57am UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438/12 "2005-09-27T05:57:51Z")
> [@Walton Firm](#): > > No he’s not. There are several non-supernatural possible explanations for why the season in which you are born might affect some of your biological traits. **Yerba buena** named one possibility (admittedly, a rather far-fetched one) in his OP. I just named another one. Nonsense. Please see my previous post. I can see absolutely no valid possibility of the season of one’s birth having any affect whatsoever. You’d have to have some awfully damned compelling evidence if you want anyone to accept that notion. Do you have it? Furthermore, the so-called “Mars Effect” **IS** astrology! The study was performed in order to prove or disprove **astrology**. It was performed by **astrologers**. The results were cited by the authors of the study as proof of **astrology**. > [@Walton Firm](#): > > Even if the answer to the OP’s question were affirmative, that’s still a _huge_ difference from how an astrologer claims to be able to deduce all kinds of minute details about your character from the exact moment of your birth. You are mistaken. Astrology is, at root, nothing more than the belief that the time of your birth in any given year affects your life in some way. There are hundreds or thousands of differences between various astrologers, but they all have in common that belief. The OP is indeed asking if astrology is valid. ---
**Author:** ![Marley23](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Marley23](https://boards.straightdope.com/u/Marley23)\ **Post date:** [September 27, 2005, 6:07am UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438/13 "2005-09-27T06:07:34Z")
> [@ambushed](#): > > The premise of astrology is that your birthdate influences your life, particularly one’s success in life. I think it’s much more accurate to say the premise of astrology is that the positions of the stars and planets influence your fortune. If **Shagnasty** ’s link is correct - and I’ve heard things like that before - then clearly it’s possible that one’s birthdate can have some influence on your life. Assuming that is indeed the date of birth, or more accurately the timing of the pregnancy, that is responsible. On the other hand, the Mars effect is astrology, and some of the things **yerba buena** are just speculation about the personalities of parents based on when they conceive. ---
**Author:** ![ambushed](https://avatars.discourse-cdn.com/v4/letter/a/3bc359/32.png) [@ambushed](https://boards.straightdope.com/u/ambushed)\ **Post date:** [September 27, 2005, 6:32am UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438/14 "2005-09-27T06:32:06Z")
> [@Marley23](#): > > I think it’s much more accurate to say the premise of astrology is that the positions of the stars and planets influence your fortune. I think the two statements are equivalent, but I won’t quibble further. > [@Marley23](#): > > If **Shagnasty** ’s link is correct - and I’ve heard things like that before - then clearly it’s possible that one’s birthdate can have some influence on your life. Hmmm… Well, I’ll need to eat some crow, then. But it is only fair to point out that it’s only _incidentally_ that the season might cause this (and the hypothesis is still preliminary and controversial). The date and time of birth are not the proximate cause, the vitamin D deficiency is. I think the confusing aspect is that the OP actually asked _two_ different questions, the first is equivalent to asking if astrology is true, but the second asks if any “subtle behavior of a parent” at the time of conception can affect a child. The answer to the first question is “no”, while the answer to the second is “apparently yes”, since it is true that a vitamin D deficiency results from a “subtle behavior of a parent”. ---
**Author:** ![Marley23](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Marley23](https://boards.straightdope.com/u/Marley23)\ **Post date:** [September 27, 2005, 6:35am UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438/15 "2005-09-27T06:35:53Z")
> [@ambushed](#): > > But it is only fair to point out that it’s only _incidentally_ that the season might cause this (and the hypothesis is still preliminary and controversial). The date and time of birth are not the proximate cause, the vitamin D deficiency is. Right. As I said, the timing of the pregnancy is the cause of that deficiency, if that’s true. > [@](#): > > I think the confusing aspect is that the OP actually asked _two_ different questions, the first is equivalent to asking if astrology is true, but the second asks if any “subtle behavior of a parent” at the time of conception can affect a child. Although even then, I don’t think it’s true in the way the OP suggests it could be. ---
**Author:** ![Walton\_Firm](https://avatars.discourse-cdn.com/v4/letter/w/45deac/32.png) [@Walton\_Firm](https://boards.straightdope.com/u/Walton_Firm)\ **Post date:** [September 27, 2005, 4:20pm UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438/16 "2005-09-27T16:20:47Z")
Yes, the Mars effect is astrology, in the sense that it was originally discovered by an astrologist seeking to demonstrate the truth of astrology. However, just because the effect is there, that doesn’t mean we have to accept his hypothesis as to the explanation. Which is fortunate for us skeptics, because the correlation is a bit too strong to easily make it go away completely. Like **Marley** , I dispute that _any_ claim of a correlation between one’s birthdate and other traits automatically counts as astrology, even when said correlation can be explained by something as mundane as the person’s age relative to their classmates. In this case, the direct link between the planet Mars and the person’s athletic prowess is a red herring – the actual explanation lies in something which just happens to be correlated with both. To claim that the position of a planet at one’s birth influences one’s life is silly superstition; to notice a pattern in a set of data and then look for a scientifically plausible explanation is just good science. Am I convinced that the effect is real? No – it might still all be a case of finding accidental patterns in randomness. There is evidence, but not “awfully damned compelling” evidence. But even if the effect is real, it hardly falls into the same category of “extraordinary claims which require extraordinary explanation” as the more common (and much more ambitious) claims of astrologers and their ilk. ---
**Author:** ![easy\_e](https://avatars.discourse-cdn.com/v4/letter/e/eb8c5e/32.png) [@easy\_e](https://boards.straightdope.com/u/easy_e)\ **Post date:** [September 28, 2005, 1:15pm UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438/17 "2005-09-28T13:15:55Z")
I disagree with the premise. A large portion of pregnancies are unplanned (I’ve heard as many as half, but I’m not saying that’s a fact). I think those should be more or less evenly distributed throughout the year. Perhaps times when more couples are likely to be having sex (New Year’s, Valentine’s), the births go up. Of couples that plan their pregnancies, most that I know say “Okay, let’s start trying to have kids.” And then they try until they become pregnant. Because not every couple will become pregnant during their first month of unprotected intercourse. To use your teacher example, I don’t think a couple in which the wife’s a teacher will try druing the 9 months before June or July, not become pregnant, then say “Oh well, we’ll try again next year!”. ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [September 28, 2005, 2:22pm UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438/18 "2005-09-28T14:22:14Z")
Wouldn’t it be a good idea to come up with a null hypothesis and hypothesize: \* Test scores have no correlation to birthdates.\* Then get a sample population and chart their birthdays and test scores, etc? Then you run the numbers through a chi square goodness of fit test to see if any differences are statistically significant enough to debunk the null hypothesis (which would then mean test scores do have a correlation to birthdates). ---
**Author:** ![Fear\_Itself](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fear_itself/32/19637_2.png) [@Fear\_Itself](https://boards.straightdope.com/u/Fear_Itself)\ **Post date:** [September 28, 2005, 2:32pm UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438/19 "2005-09-28T14:32:42Z")
I ahve always wanted to do a correlation between birthdates and the [Forbes 400 Richest Americans](http://www.forbes.com/lists/2005/54/Worth_1.html). I would think their birthdates would be fairly easy to discover, as most of them are prominent citizens with published biographical information. If there is nothing to it, it should be a fairly even distribution, right? ---
**Author:** ![Bryan\_Ekers](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bryan_ekers/32/183_2.png) [@Bryan\_Ekers](https://boards.straightdope.com/u/Bryan_Ekers)\ **Post date:** [September 28, 2005, 4:09pm UTC](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438/20 "2005-09-28T16:09:04Z")
I don’t get why **ambushed** is going on about astrology, either. It’s not difficult to imagine the possibility of a significant difference in physical and intellectual maturity between groups of children entering kindergarten, if one group was born shortly after the cutoff (and thus is around 5 years, 11 months in age) and one group was born shortly before it (and thus is around 5 years, 1 month in age). Given the speed of human development, those extra ten or eleven months could be _very_ significant, and this has nothing whatsoever to do with astrology or any other pseudoscience. [Next page](https://boards.straightdope.com/t/birthday-dependence-of-test-scores/322438.md?page=2)