New baby research from the University of Cambridge has found newborn girls spend a greater share of their attention on a face than newborn boys do, although both sexes prefer a face to a moving object.
While the difference was modest, Tobias Grossman, the leader of the University of Virginia’s Baby Lab, said the work offers interesting new ways to understand human development. He talked with UVA Today about the work.
Q. What did the study find about newborns’ attention to faces?
A. From the first hours of life, human babies are drawn to faces. In the study, the babies looked longer at the face, 32.0 seconds on average, than at the object for 24.8 seconds.
Q. How did girls’ and boys’ responses differ?
A. For the boys-versus-girls question, the most important numbers are these: girls and boys looked at the face for about the same amount of time, 33.2 seconds for girls and 30.9 seconds for boys. That 2-second gap was not statistically reliable, and neither was the difference in how long they looked at the object, 22.9 seconds for girls, 26.5 for boys.
Q. Then where does the sex difference come from?
A. It appears only when you look at how each baby divided attention between the two videos. Girls spent, on average, 58.5% of their looking time on the face; boys spent 51.2%. That is a gap of about 7 percentage points. Put simply, girls on average favored the face, while boys on average split their attention roughly evenly between the face and the object. Importantly, boys did not prefer the object.
Q. Does the finding show that prenatal hormones shape male and female brains?
A. No. The study didn’t measure hormones or brains; it measured where babies looked during a single 70-second test. Prenatal testosterone is one possible explanation, and the authors discuss it, but they are clear that other explanations fit the data just as well.
It is a carefully done study of a very hard-to-test age group.
One is maturity. There is evidence that newborn girls are, on average, slightly further along developmentally than boys. In this study, girls were also more likely to finish the test on the first try. A slightly more mature visual system may simply be better at taking in a complex, moving face.
Q. How does this study compare with earlier research?
A. A widely cited 2000 study from the same Cambridge lab reported that newborn girls looked more at a face, and newborn boys looked more at a mechanical mobile. That study drew methodological criticism; for example, a live experimenter served as the face, and the two stimuli were shown one after the other. The new study addresses several of those concerns. It is a carefully done study of a very hard-to-test age group.