Blondes are just as intelligent as people with darker hair.
Study author Jay Zagorsky publishes his findings in the journal Economics Bulletin.
Elle Woods, a character played by Reese Witherspoon in the 2001 hit movie Legally Blonde, is quite possibly the definition of the so-called dumb blonde stereotype; an attractive, outgoing sorority girl who is perceived as being more interested in shopping and socializing than getting an education.
But by the end of the movie, Woods proved that she was no less intelligent than her peers, graduating with high honors and landing a job at a prestigious law firm.
Now, a new study moves us from fiction toward fact, finding that blondes are just as clever - if not smarter - than darker-haired individuals.
The popular notion that blondes are intellectually challenged is something that has been held for years, so much so that the stereotype even has its own category of humor, labeled "blonde jokes."
But Zagorsky says the blonde stereotype is no laughing matter; it can have serious economic consequences, affecting employment, promotion and other social experiences.
"This research asks and answers 'Are blondes really dumb?' The question is important because intelligence is a trait many firms seek when hiring," notes Zagorsky. "If blonde women are incorrectly perceived as less intelligent than women with other hair colors, then blonde women might be sorted into lower paying and less mentally taxing jobs than they have the ability to handle."
Slightly higher IQ for blonde women
To reach his findings, Zagorsky analyzed data from the National Longitudinal Survey of Youth 1979 (NLSY79), involving 10,878 Americans who were aged 14-21 at their first interview in 1979.
In 1980, all participants completed the Armed Forces Qualification Test (AFQT), a test of word knowledge, paragraph comprehension, math knowledge and arithmetic reasoning that is used by the Pentagon to assess the IQ of all new recruits.
Five years later, participants completed a survey in which they were asked to disclose their natural hair color. Zagorsky then compared the results of the AFQT test with participants' hair color.
Since hair color varies by race and ethnicity, Hispanics and blacks were excluded from the study in order to prevent any bias in the IQ tests.
Zagorsky found that blonde-haired white women had a slightly higher average IQ than darker-haired women; the average IQ for blonde women was 103.2, compared with 102.7 for women with brown hair, 101.2 for those with red hair and 100.5 for black-haired women.
Additionally, compared with darker-haired women, blonde women were slightly more likely to be in the highest IQ category and marginally less likely to be in the lowest IQ category.
Among men, those with brown hair had the highest IQ at an average of 104.4, though blonde-haired men came a close second, with an average IQ of 103.9 - an insignificant difference that suggests blonde men are just as intelligent as those with darker hair.
Blondes 'are definitely not dumber'
While the results show blonde women have a slightly higher IQ than those with darker hair, Zagorsky notes that the difference is not statistically significant:
"I don't think you can say with certainty that blondes are smarter than others, but you can definitely say they are not any dumber."
One key limitation of the study is that some women lied about their natural hair color; Zagorsky estimates that around 3.5% of women incorrectly reported their natural hair color as blonde. While it is unclear how this may have impacted the results, he believes it is unlikely to change the main finding.
Zagorsky says his study is unable to pinpoint a genetic link between hair color and intelligence, but he did come across one factor that could explain why blonde women showed marginally higher intelligence than those of other hair colors: blonde women grew up in homes with more reading material.
"If living in a more literate environment is truly the driving reason for higher blonde intelligence, then the solution for people who wish they or their children were smarter is not to dye or bleach their hair," he notes. "Instead, the prescription is to provide or engage in more intellectual stimulation, such a reading books."
Last December, Medical News Today reported on a study suggesting that the effect of genes on intelligence may be influenced by social class.