Friday, June 16, 2017
Unborn Babies and Faces: What to Make of This?
I recently received an email from an anti-abortion group who referenced a recent study about the visual behavior of 34-week fetuses—still 6 weeks before they would typically be born. Although the number of abortions that take place at that point in gestation is vanishingly small, my correspondents wanted to use the study to argue against terminating pregnancy at any point. That’s what they do, so I won’t argue with it, but I’d like to look at the study itself and what it means about early development of human beings.
You can find a discussion of the study in a number of places, but here’s one you might try: www.usatoday.com/story/news/2017/06/08/womb-view-fetuses-can-recognize-faces-while-still-inside-mom/102625620/. The researcher was able to shine a bright light through the uterus and amniotic fluid that surrounds the fetus and at the same time to do imaging that would reveal how the fetus turned toward the light. What does this have to do with faces? Well, there were two kinds of lights, each involving three dots arranged in a triangle, which adults might perceive as “two eyes” and “one mouth”. The lights were shown either in a position where they looked like the basic elements of a face, or “upside down” so that the “mouth” was above the “eyes’. The babies moved to “look at” the right-side-up face more than at the upside down non-face.
Because the fetuses discriminated between the two patterns by moving differently, it was concluded that they could were reacting differently to things like faces than to other things that were not so face-like. It was that discrimination that led to the statement that they recognize faces while in the womb. It would be less exciting but a good deal more accurate to say that they respond differently to the face-like triangle than to the other. They do not recognize faces in the adult sense of being able not only to tell one actual face from another but even to know which person has which face. No such claims were made, and for good reason. You might as well say that unborn babies recognize point-down triangles as that they recognize faces in the sense that even a three-month-old does.
Under ordinary conditions, there is no light inside the uterus, so an unborn baby has no visual experience whatsoever. He or she has had no opportunity to learn what people, dogs, moons, or crib bumpers look like. Any visual response that occurs—either in the womb or right after a preterm or full-term birth—has to be produced by functions that are built into the visual system as a result of genetic commands to the developing brain. (Brain? Yes, because developmentally the retina or light-sensitive part of the eye is actually a part of the brain.)
The visual system is the last sensory system to begin its development in the prenatal period, so we might not expect vision to be very good at 34 weeks gestational age—it’s not great at 40 weeks or full term. When babies look at faces after birth, they tend to scan the eye areas and the mouth area a lot, but as is shown by all the comments I get from mothers worried about lack of eye contact, the very young babies do not look at faces very much. They just look at them more than they look at other things. Babies in the first month or so after birth are also very limited in their ability to see objects that are too close or too distant, so even then they do not get a lot of time to look at and learn about faces.
So how does it come about that before birth they can “look” at a face-like pattern and respond to it as if it means something special to them? The most likely reason is that in their still very immature brains they already have feature detectors that are activated by a seen pattern. A feature detector is a cell in the visual system of the brain that is connected to a particular part of the retina and responds only to certain kinds of images that fall on that retinal area. This is a lot easier to demonstrate with frogs than with human beings (who tend to excuse themselves when you want to do things to their brains), but frogs have feature detector cells that are “fly detectors” and become activated when an image the size and shape and speed of a nearby moving fly falls on the retina. The frog feature detectors signal the tongue, and zip, the tongue nails the fly. Mammals too have feature detectors, although fortunately they do not make us catch flies with our tongues. Face detectors are among them—brain cells that are activated when the image of a shape that resembles a face falls on part of the retina. Even sheep have face detectors that respond to human faces. Sheep “recognize” faces in the same sense that unborn babies do.
It’s really interesting and important for researchers to show how early and how gradually human sensory and other systems begin to develop. Those systems don’t just “come on line” instantaneously at some point, and although birth is a dramatic event in the course of development, not all developmental changes are closely related to it. However, when the researchers have done their job, it’s also important for the media and their audience not to jump to conclusions about the implications of findings. We humans don’t seem to have feature detectors that respond to exaggerations!