Read My Eyes

"One of the difficulties of course with babies is that they don’t speak yet at the age at which we would like to study them," says Dick Aslin, professor of brain and cognitive science at the University of Rochester, who is leading the research. "So, by using a measure like eye movements we can get a silent assessment of the knowledge they have about a particular topic."

Before now it wasn’t possible to track infant eye movements because eye trackers used to be mounted on the head, making them too big and heavy for babies to wear. But remote eye tracking systems solve that problem. At the Rochester lab, researchers have the mother hold her baby on her lap in front of a TV screen and fit the infant with a knitted cap that has a small magnet inside. The magnet guides an infrared camera that tracks the child’s eyes even when he or she wriggles around, as inevitably happens.

"This technology has really opened up the possibility of recording their eye movements continuously over a fairly long period of time, and therefore we can measure their learning," says Aslin.

Learning to look

To do that, researchers show the baby a stimulus on the screen, such as a square or cross shape. This is followed by a reward in the form of an animation on either the right or left side of the screen (depending on whether it was a cross or a square). Aslin and his team have found that babies quickly learn where to look for the movie based on the shape’s category. "What’s really amazing is how quickly they can learn things in a matter of minutes in the laboratory setting," Aslin says. "I think that’s the most surprising thing about this work."

But the experiment doesn’t end there. Babies are given a brief rest and then asked to apply their new knowledge. When shown something they’ve never seen before—a shape of a different color—they usually look in the correct direction to see the movie. "They will generalize. That is, they will place that object in one of those two categories. And of course because we can’t ask them questions, this eye movement technique has been revealing of their ability not only to form categories, but to learn new items that go into categories they’ve just learned," explains Aslin.

Researchers found, however, that when they rotate what should be a familiar shape, babies become confused, suggesting that they have to learn to ignore certain features, in this case orientation, in order to be able to categorize objects.

The team plans to expand its research by testing infants’ space perception, according to Bob McMurray, a graduate student who is working on the studies. After training babies to look in one direction after seeing their mother’s face and another direction after seeing their father’s face, they’ll start to hide certain facial features to see exactly what it is that babies pay attention to.

They also plan to study how babies perceive objects that are occluded by other objects. (When you look at an object, it’s often partially hidden by something. But you can still tell what it is by the part that’s visible.) "If you think about it, virtually everything we see is occluded by something else. We never see an object in its entirety," says McMurray. "So a baby that can’t fill in the missing parts of an object has a very different visual experience than a baby who can."

Additional experiments will include using sounds instead of shapes, in the hope of understanding how babies acquire language, according to Aslin.