Ultrasound of fetus (Image: Kirsty Dunn & Vincent Reid)

We don’t remember what it was like to be a fetus. We don’t remember what we heard or smelled, and we certainly don’t remember what we saw. So fetuses, their development, and their experiences are a natural curiosity. When and how do fetuses start taking part in the human experience? Can they recognize faces from the womb?

One team of British scientists thinks their research demonstrates that fetuses prefer face-like visual cues. Like, fetuses can literally recognize faces projected onto the inside of the uterus. While understanding fetal development is important, other researchers don’t think that the study proves its hypothesis. We’ll let you be the judge.

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The research begins with “bottom heavy” and “top heavy” geometric patterns—three dots arranged in either a triangle or an upside-down triangle. They essentially repeat experiments done in the past with newborns, that certain geometric patterns, in this case, the upside-down triangle, look more like faces. The researchers determined the orientation of the fetus, then shone either arrangement of lights onto the belly of 39 pregnant women in their third trimester, either to the right side or left side of the fetuses’ heads. They measured and compared with ultrasound how much the fetuses turned their heads.

The results seem to prove their hypothesis: on average, fetuses turned their head way more towards the upside-down triangle of dots (the face-like ones) than they did to the regular triangle of dots, according to the research published today in Current Biology.

Image: Kirsty Dunn & Vincent Reid

Simply doing this type of research has importance. “It’s the first time I’ve seen evidence that the human fetus differentially responds to patterned light,” Mark Johnson, Co-director of Birkbeck, University of London’s Centre for Brain and Cognitive Development, told Gizmodo. There have been plenty of studies on how fetuses respond to sounds, but very little information on responses to light. And newborn instincts like the sucking, grasping and even head turning are important for survival. So this line of research can add evidence to when and how fetuses begin developing those instincts.

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But he and other researchers looked at the paper with plenty of skepticism. One of the paper’s sentences stood out to Johns Hopkins developmental psychologist Jane DiPietro, who lead the Johns Hopkins Fetal Development Project. That sentence: “It should also be noted that the results of the present study do not imply that the fetus can respond to faces presented externally under everyday circumstances.” This stands nearly in contrast to the paper’s splashy title, “The Human Fetus Preferentially Engages with Face-like Visual Stimuli.”

“I have less concern regarding their conclusion. The notion that a preference for faces begins before birth as an innate priming is not implausible,” she said. “What bothers me is that this study does not show that in any way. I’m dismayed at the title of it. I find it sensational and not based on the data.”

And there’s plenty of places to be skeptical. Babies’ vision continues developing after birth, and newborns could have difficulty distinguishing between the different patterns or resolve things at a distance. For instance, the number of head turns made by a fetus is an inexact measure. Also, while the researchers shined three dots of light onto the baby bump, they assumed—but did not see—what pattern the fetus was seeing. And probably more importantly, fetuses spend most of their time asleep, she said. The researchers said they ruled out cases where the baby was in a deep sleep, but the fetuses could have been lightly sleeping and rousing to different brightnesses of light. She thought there were simply too many assumptions along each step of the way.

And even those core assumptions might be wrong. Doubt has been cast on the working assumption that infants prefer face-like geometric patterns.

So why even cover this study? There are a lot of reasons. Splashy paper titles frequently get covered without skepticism, and press releases might get shared without presenting study limitations. And DiPietro worried that folks looking to make some money might use these results might create products showing faces to fetuses in the womb, the same way that people play music for fetuses in the womb. “Nature has designed the perfect system” to develop a child, she said. “Adding external stimuli thinking you’re doing something to foster development is interfering with the system.”

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The study’s authors didn’t respond to a request for comment. But rather than throw away this evidence or take it as fact, Johnson said other scientists need to do a more rigorous replication study with fewer sources of bias or assumptions.

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So if you’re pregnant and next month someone tries to sell you some sort of science-backed face-flashlight to shine into your belly for your fetus, don’t buy it. The science is far from settled, and no one knows whether it’s even a good thing.

Update 6/12/17 5:20 PM: The paper’s author, Vincent Reid responded to our request for comment. He highlighted that they are specifically referring to face-like visual stimuli, not faces. “Our paper reports a technical term that, unfortunately, can be incorrectly interpreted as a “face” by people who are not familiar with visual perception research,” he said in an email, and stressed the importance of his methods. “This method has the potential to open up the field of visual perception in the fetus. That in itself is a huge leap forward.”

Additionally, Reid had some comments on our skepticism. He pointed out that the study attempts to correct for things like poor visual acuity and fetuses spending much of their time asleep, as well as for the fact that they could not see what the fetuses are seeing. He agreed that head turns are an imprecise measurement and that there were assumptions made along the way. However, he thought that the results “strongly suggest the assumptions are correct,” and the results were consistent with the hypothesis.

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[Current Biology]