..for some commonly agreed-upon, objective, quantitative, non-discriminatory intelligence criterion.

Before you rush to close this as a duplicate, yes, I am aware of this other question that treats this problem. However, the accepted answer fails to take into account other factors such as education level and cultural background, to name a few. I'm not interested in lumped "statistics" that compares apples to oranges, I'd rather see a scientific study that:

  • Uses a sufficiently large sample size to compensate for Law of Large Numbers. The sample may or may not be a representative of the population in any given country/region, it could be biased towards certain society groups (e.g. university students or kids) or genders, but that is fine, as long as it is able to demonstrate a strong correlation (or lack thereof) between the factors for that specific sample. If and how these findings can be projected to a larger population group is another question entirely.

  • Performs the study on a group with similar cultural and educational backgrounds, for example among students in an university, or even a whole country. Country-to-country comparison is mostly useless to draw any sort of meaningful conclusions due to the lack of a common objective performance criterion.

  • Uses a quantitative performance criteria. Standard IQ tests qualify, but any other sufficiently objective criterion is okay, for example grade(s) received on a course or the overall grade achieved in an educational programme, results from standard tests or state maturity exams, etc.

It probably goes without saying, but "blondes" are defined here as "natural blondes" as opposed to dyed blond wannabes. It's another question entirely whether dying one's hair blond (or dark, for that matter) has any effect on intelligence.

Bonus points for studies performed on a single-gender group which avoids gender bias.

  • 4
    I don't see the point. You'd put anybody with naturally dark hair to same group, while that would cover most of the world. Thus if you'd take US as example, you'd put eg. Native-American, African-American, Asian-American, Italian-American, Jewish-American, Mexican-American etc. in one group. Which is far to diverse group to draw any conclusions.
    – vartec
    Commented Mar 12, 2012 at 15:01
  • 1
    @vartec: I honestly can't see how ethnicity plays any role in this, unless you are trying to assert that certain ethnic groups perform worse generally than others, all else being equal. Besides, not every country in the world is as ethnically diverse as the US. Commented Mar 12, 2012 at 15:21
  • 1
    How exactly is this not a duplicate?
    – Tom77
    Commented Mar 12, 2012 at 20:03
  • 1
    "I honestly can't see how ethnicity plays any role in this" - you may have to give this some more thought. I cannot see how you can separate ethnicity from this.
    – Oddthinking
    Commented Mar 12, 2012 at 23:27
  • 2
    So the questions could be rephrased as "is there any correlation between measured intelligence and mutations in the MC1R or TYRP1 genes that determine hair colour" (mutations in TYRP1 cause blondeness in melanesians, MC1R variants in Europeans) see here and here. Seems unlikely, but is testable across racial boundaries.
    – matt_black
    Commented Aug 24, 2012 at 13:10


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