Thanks to nature, nurture, and their lifelong collaborative efforts, there’s plenty to ponder on the differences between men and women. Often this pondering seems, at an individual level at least, pointless. Whether men have better spatial abilities or women are better lie detectors doesn’t much affect whether I can squeeze into a particular parking spot or discern whether an invitation was really “lost in the mail.”
When asking for a raise, on the other hand, knowledge of gender differences may be important. And if you happen to be a language acquisition researcher, so are differences in age of acquisition. Because the truth is, when designing a study, one would do well to remember that girls hit linguistic milestones reliably earlier than boys.
Girls acquire their first words earlier, as well as their first sentences. (Not all girls, of course, so please don’t worry if this isn’t true of your daughter—language development is a strange and highly variable process.) One recent study, conducted as part of the Language Development Project by Şeyda Özçalışkan, now at Georgia State University, and Susan Goldin-Meadow of the University of Chicago, followed 40 infants from the ages of 14 to 34 months. Every four months, a research assistant showed up at a participating family’s house with a video camera and recorded the infant as he played with his toys, threw his sippy-cup across the room, and otherwise eked out a babyish existence.
The researchers found that on average girls began producing multiword utterances at 17 months. Boys hit this milestone at 21 months. The gender difference does not seem to be driven by extremely fast or slow learners: at 14 months, 45 percent of girls were producing multiword utterances, but none of the 18 boys in the study were. (I do wonder whether collecting the data at four-month intervals as opposed to, say, one-month intervals artificially inflated the size of the gender gap.)
Intriguingly, Özçalışkan and Goldin-Meadow also found that girls’ dominance could be extended to another milestone: word and gesture combinations. (Specifically, the researchers were interested in instances where both speech and gesture contributed new information, rather than simply reinforcing each other—for example, a child saying garbage and pointing to her beans rather than a trashcan.) Because gesturing is much easier on working memory than is speaking (not least because it allows infants to bypass newly learned vocabulary), infants tend to use simple combinations of gestures and words before they use combinations of different words in order to communicate the same ideas. The researchers found this is to be true for both boys and girls. But girls began combining words and gestures at around 16 months, boys at 19 months.
Why do girls show such linguistic precocity? I’m not sure anybody really knows. In the study I just described, caregivers didn’t appear to be speaking and gesturing any differently to their sons or daughters, using “roughly comparable numbers” of speech and gesture combinations. It could be, then, that girls are better at understanding relations between concepts, or mapping concepts to symbols. Alternatively, the researchers point out, girls may be more skilled, or at least more motivated, when it comes to imitating fine motor movements. Fine motor movements are crucial for producing gestures and may well be a precursor for speech (which, of course, requires its own set of fine motor movements).
Regardless of why girls tend to reach these milestones earlier, boys do eventually catch up. Özçalışkan and Goldin-Meadow report that by the time children began producing sentences containing multiple verbs (e.g., Make it fall, What are we going to do if it rain?) at around 30 months, the gender gap had disappeared.
Whether or not it reemerges later in life is a thorny, contentious question (true of most inquiries into sex differences). But it’s not my question. Let the psychologists studying the rest of the lifespan deal with that.
