I've Got Those Evidentiary Blues (and Pinks)

08/30/2012 02:01 pm ET | Updated Oct 30, 2012

Co-authored with Jo Paoletti

Girls like pink and boys go for blue. There must be something biological behind this preference, right? Can we really link pinks and blues to innate sex differences? Science, and for that matter any scholarship, is about evidence. When can an observation count as evidence for a particular conclusion? Is it strong evidence, weak evidence, or just plain irrelevant? The ongoing conversation about gender and color preference highlights the problem.

One of us (Jo Paoletti) is an expert in dress history and has argued at length that the gender division in infant and toddler fashion is fairly recent and far from universal. The pink-for-girls/blue-for-boys divide used to be just the reverse in Belgium and parts of Germany and Switzerland. And pink-blue symbolism did not spread outside Europe until after the globalization of the children's clothing market. In the United States there seems to have been no commonly accepted gender significance for infant clothing color until the middle of the 20th century. In fact, before 1920, baby clothing was almost completely gender-neutral.

The facts that the pink/blue gender distinction is historically new and not universal would seem to put the kibosh on the idea that gendered color preference is innate. But at least one psychologist has questioned the historical evidence. And therein lies the argument. Marco del Giudice recently published a letter in the journal Archives of Sexual Behavior calling the kind of evidence Paoletti uses -- museum objects and manuscripts -- "anecdotal." To be fair, both del Giudice and Paoletti agree that her argument has been misread as a claim that color preference once reversed in the United States. But this is not the point we make here. The question is, what counts as good evidence of a historical shift in consumer culture?

True to the quantitative traditions of his own field, del Giudice counts pink and blue references using an app called Google Ngram Viewer. It's pretty impressive to someone who loves numbers. The Google app searches word appearances in some 5 million English-language books. Del Giudice searched for phrases such as "pink for girls" and "blue for girls." He found no evidence of color-preference reversals, but he found support for Paoletti's idea that stronger color-gender associations appeared during the 1950s. In contrast, and true to the traditions of the cultural historian, we do not put as much stock in counting words from books. A book search doesn't capture the sources with the strongest evidence. Mail-order catalogs, images of actual clothing, paper dolls, birth announcements, and manuscript sources such as lists of shower gifts in baby books provide a more direct way to understand everyday practices that books often ignore. Baby albums, for example, make it clear that in the 1930s, newborn boys and girls across the United States received both pink and blue dresses and sweaters, proof that our current "rules" had yet to completely jell. Before 1940 there was a stronger correlation between clothing color and hair color than clothing color and sex -- blue was for blonde babies, pink for brunettes.

There you have it: What counts as good evidence to historians may not wash for psychologists, and vice versa. But what about biological claims? Again, there is a question of evidence. Del Giudice concludes his letter by citing two articles that gesture toward the idea of innate perceptual bias. One, on adults, actually shows a clear effect of culture on gender differences in color preference; compared with men and women from the United Kingdom, Chinese men and women show very little difference in hue preference. The other demonstrates that after the age of 2, girls prefer pink while boys avoid it.

It's important to think developmentally about this. Smack out of the womb, infants seem to have no color preferences at all. In fact, newborns don't really see much in the way of color. Rainbow vision develops during the same period that adults offer up differently colored worlds to boys and girls. Four-, 6-, and 9-month-old children like blue and red, but not pink. One- and 2-year-old girls and boys like stronger colors (red, not pink; strong blue, not pale blue). Still, despite this perceptual bias against pink, by the time they can talk, many European and American girls go for the pink. When you use developmental evidence, starting from before boys and girls divide up into pro- and anti-pink factions, and ending after the great color divide is in place, there is not much support for inborn differences. Something more interesting is happening: Our little children gradually absorb their surroundings until they become part of their little color-preferring bodies. Understanding how this happens requires us to start at the beginning and study the developmental process, with bodies, experience, and environment all wrapped up into one.