New parents can come up with a seemingly endless array of vexing questions about their infants, from the best brand of stroller to the ideal song to sing them to sleep. The questions begin well before the child is born: what type of clothing should you purchase? What kind of crib?
One question Greta and I dwelled on quite extensively when Jim was an infant was color. We were renting an apartment and couldn’t paint the nursery, so we wondered about the color of the toys we bought and the blankets and other bedding for the crib. Would a purple outfit be appreciated? What about a multi-colored activity gym? Would a white blanket be too boring? At the time, black-and-white toys were all the rage, the thought being that infants needed high-contrast objects to be stimulated the most.
While it is true that the youngest infants don’t distinguish colors as well as older infants, by two months of age, most babies can tell the difference between most colors and white. Do they prefer particular colors? In 1975, M.H. Bornstein exposed infants to eight different pure colors of the same luminance and found that they looked longer at red and blue, and less at greenish colors like blue-green and especially yellow-green. This study may have been the inspiration for the yellow-green “Mr. Yuck” stickers intended to discourage toddlers from playing with poisonous substances.
But there are some problems with Bornstein’s study. While the colors he showed babies had a similar luminance, the human experience of color perception actually varies across three different dimensions: hue, saturation, and brightness. We don’t directly perceive the physical luminance and wavelength of a light, we perceive these other qualities. Even if only the wavelength of a light is changed, we’ll see it as changing along all three dimensions: hue, saturation, and brightness. Perhaps babies actually prefer a particular saturation or brightness level, not a wavelength. This picture shows two of the three dimensions of color, hue and saturation:
The larger rounded figure represents all the colors we can see, but only some of them can be reproduced on a computer monitor: the central triangle. The small numbers around the rounded figure correspond to physical wavelengths: about 450 nm appears blue, while 600 seems red. Moving towards the edge of the figure gives us more saturated colors, while the center is the least-saturated point, what we see as white. The computer displays a mixture of red, green, and blue light to generate the colors we see.
Most computers have a way of choosing colors that references hue, saturation, and brightness — if you can find the controls on your computer, it can be fun to play around with them
Iris Zemach, Susan Chang, and Davida Teller showed 235, 3-month-old babies a set of colors that maintained the same brightness while varying the hue and saturation. The babies looked at two disks on a computer display: one white, and one colored. The sessions were videotaped, and an observer who couldn’t see the disks recorded how long the babies looked at each disk. This figure shows the results:
The larger the dot, the longer the babies looked at that color rather than the white disk. As you can see, blue and purple were preferred substantially more than the other colors. While it also appears that more saturated colors were preferred, saturation wasn’t the best predictor of color preference. This graph compares color purity with actual preference:
The dotted lines show gradations of purity (which corresponds roughly to saturation) while the bold lines show gradations of preference (with preferred colors to the outside). As you can see, the two maps don’t match. Babies don’t have a saturation preference, they have a hue preference.
But perhaps babies simply can’t detect certain colors, and that explains the preference. In a separate experiment, the researchers showed just one disk of color at a time, on either the right or left side of the screen. Once again they measured how long the infants looked at each side of the screen, figuring if they looked longer at the colored area that’s an indication that they can detect it. They found no significant correlation between detectability and preference. In fact, purple was better-detected than blue, while blue was preferred over purple.
So Zemach’s team was able to confirm the decades-old study by Bornstein, and also to extend it to the more limited set of colors reproducible on a computer screen: Babies do have color preferences, and these preferences seem to be mostly determined by hue. Blues and purples are babies’ favorites, while greens, yellows, and reds are liked less. Bornstein did find that babies liked red more than Zemach’s team, but that can be explained by the wavelength used in his study: a deeper, more purplish 630 nm, compared to a more orangeish 600 nm in the Zemeach et al. study.
Does this mean expectant parents should run off to buy purple and blue toys, blankets, and car seats for their babies? In the end, I doubt it would make that much difference in a baby’s life. The first few months of infancy are over quite quickly, and are spent mostly sleeping. What matters more is the care, love, and attention given to a child over her lifetime. But it’s still interesting to see how babies’ visual systems develop, and how at just 3 months of age they do appear perceive colors in a way that is analogous to adults.
ZEMACH, I., CHANG, S., & TELLER, D. (2007). Infant color vision: Prediction of infants’ spontaneous color preferences Vision Research, 47 (10), 1368-1381 DOI: 10.1016/j.visres.2006.09.024