It is dark in the womb—but not that dark. Human flesh isn’t fully opaque, so some measure of light will always pass through it. This means that even an enclosed space like a uterus can be surprisingly bright. “It’s analogous to being in a room where the lights are switched off and the curtains are drawn, but it’s bright outside,” says Vincent Reid from the University of Lancaster. “That’s still enough light to see easily.”
But what exactly do fetuses see? And how do they react to those images? To find out, Reid shone patterns of red dots into the wombs of women in the third trimester of their pregnancies, and monitored the babies within using high-definition ultrasound. By looking at how the babies turned around, Reid showed that they have a preference for dots arranged in a face-like pattern—just as newborn infants do.
“This is the first time that anyone’s been able to deliver an image to a fetus,” Reid says. And it will finally allow scientists to study the mental abilities of humans at the earliest possible stage of our development—before we are even born.
For decades, scientists have known that third-trimester babies can perceive sounds and other stimuli while still in the womb. For example, in 1980, Anthony DeCasper and William Fifer asked pregnant women to read The Cat in the Hat to their fetuses, again and again for the last 7 weeks of their pregnancies. As soon as the babies were born, DeCasper and Fifer gave them pacifiers. The babies could then choose to hear a recording of either The Cat in the Hat or a different children’s story, by sucking at different times. And they sucked for the cat.