Third trimester babies turn their heads in the womb to look at face-like images projected onto their mother’s bellies, according to a new study. The findings are the first to explore visual perception in fetuses and suggest that the human preference for human faces may be instinctual rather than learned.

“We have shown that shapes of light can be projected to the fetus through the uterine wall and that the fetus can distinguish between different shapes, preferring to track face-like over non-face-like shapes,” coauthor on the study Kirsty Dunn, a psychology researcher at Lancaster University in the UK, told Fatherly. “Until now, exploring fetal vision had not been attempted.”

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Before Dunn and her team launched their study, few researchers had even explored cognition in utero. Prior studies had shown that the fetal brain responds to flashes of light in the womb, so Dunn and colleagues had reason to believe that it was possible for light to travel to the fetus. But the specifics of fetal visual perception and cognition remained a mystery.

For the study, Dunn and colleagues used 4D ultrasound to watch the reactions of a small sample of 39 third trimester fetuses as different patterns of light were shined onto their mothers’ stomachs. They found that the fetuses were more likely to move their heads to follow an upside down triangular array of lights—representing the shape of a face, which widens at the top and narrows at the bottom—than they were to respond to a right-side-up triangular array.

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“Studies with newborn babies have shown that they prefer to look at faces as well as shapes that are face-like in that they have more information in the upper part than the lower part of the shape,” Dunn explains. “It is likely that the visual preference for top-heavy shapes, even before birth, is what drives their preference for human faces when they are born.”

Mark Johnson, co-director of the Center for Brain and Cognitive Development at Birbeck College in London, who was not involved in the research, told Fatherly that scientists have long known that fetuses respond to the environment, but that “the capacity of the late fetus to respond to visual information was thought to be minimal.” Johnson stresses that the study does not suggests that fetuses are staring out at the world from inside their mothers. It suggests only that they would if they could.

“It’s important to note that the way that the light patterns were presented on the mother’s belly does not reflect what would happen naturally,” he says. “Outside of the experiment, the fetus is unlikely to be presented with the light patterns these authors projected on the mother. So the authors do not claim that fetuses track the movement of other people’s faces around the womb.”

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But the results are still compelling because they lead to other questions. For instance, the techniques described in this study could provide some of the first robust tools for researchers interested in investigating the interplay between fetal vision and other areas of cognition. “Newborns can discriminate numbers and quantities,” Dunn says. “Does the fetus in the third trimester also have these capacities? If the fetus can do this too, this tells us a lot about fetal cognitive capacities.”

And, down the line, there could be clinical implications as well. “We could do assessments of fetal capacity after interventions where oxygen deprivation may have taken place, such as in fetal heart surgery,” Dunn says. “A prenatal assessment based on visual response could potentially tell us if something has gone awry…Now we may be able to do it with the fetus, too.”