Infants spend twice as much time in REM sleep as adults—but experts still know little about what happens in their brains during those hours.
Infants spend most of their time sleeping, waking up for just a few hours total every day. A lot of growth happens during those spans of shut-eye, though. Research shows that sleep is just as formative for babies’ development as are the scattered bouts of consciousness when their eyes are open and their ears are perked up. As with adults, sleeping likely helps infants retain or protect memory and learn language; some evidence also suggests it promotes healthy physical growth. Technological advances are helping to shed more and more insight on, as the University of Washington professor of early-childhood learning Patricia Kuhl has put it, “the infinite number of secrets” contained in babies’ brains.
One secret that those advances have yet to uncover: whether babies dream—and, if they do, what they dream about. “Getting inside the head of a baby,” wrote the science journalist Angela Saini in a 2013 piece for The Guardian, “is like deciphering the thoughts of a kitten.” Brains are composed of so many intangible phenomena, and the technologies used to measure the stuff that is tangible (like brain-scanning machines) are difficult to use on babies. The resulting mystery has made the topic an endless source of intrigue—and of pointed disagreement— among many researchers.
In the 1960s, as the journalist Alice Robb explains in her forthcoming book Why We Dream, the psychologist David Foulkes theorized that children seldom remember their dreams before age 9. Foulkes continued his research into pediatric dreaming over the decades and in his 2002 book on the topic concluded that humans are dreamless in their first few years of life.