By the time they are four months old, most babies can organize visual information in at least three ways: by brightness, by shape and by how close together objects are. Emily Farran, a psychologist at the University of Reading in England, tested infants by showing them images on a computer screen while cameras tracked how long they gazed at various patterns. Her results indicate that perception of brightness emerges first, by two months, in line with previous work. By four months, most infants can group objects by shape and proximity, too. “Earlier research had shown only the ability to group by shape at six to seven months,” Farran says, “and we believe we are the first to show grouping by proximity.”

Farran's interest in the development of visual perception comes from her ongoing research into Williams syndrome. Infants who have the condition have general IQs of about 60, “but their verbal abilities are far superior to their spatial cognition,” she says. Farran is now using the same tests to see how these skills develop in babies and toddlers with Williams syndrome. “Infants are being diagnosed earlier now, thanks in part to a genetic test,” she says, adding that better tracking of abilities during early development could also help doctors understand and counteract perception impairments observed in adults with the syndrome.