Babies Make Predictions, Too
In “The Adventure of Silver Blaze,” about a valuable racehorse that mysteriously disappears, Sherlock Holmes tells the hapless Detective Gregory to note the curious incident of the dog in the nighttime. But, says Gregory, the dog did nothing in the nighttime. That was the curious incident, Holmes replies—the dog didn’t bark on the night of the crime, as you would expect. A new study suggests that as babies start to figure out the world, they think a lot like Sherlock.
People often say that babies are “sponges.” The metaphor reflects a common picture of how the brain works: Information floods into our eyes and ears and soaks into our brains, gradually becoming more abstract and complex. This image of the brain is vividly captured in the “abstract thought zone” of the recent animated Pixar movie “Inside Out”—where three-dimensional experiences are transformed into flat cubist ideas.
But a very different picture, called “predictive coding,” has been making a big splash in neuroscience lately. This picture says that most of the action in the brain comes from the top down. The brain is a prediction machine. It maintains abstract models of the world, and those abstract models generate predictions about what we will see and hear. The brain keeps track of how well those predictions fit with the actual information coming into our eyes and ears, and it notes discrepancies.
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If I see something that I didn’t predict, or if I don’t see something that I did predict, my brain kicks into action. I modify my abstract model of the world and start the process over.
If “predictive coding” is right, we’re designed to perceive what doesn’t happen as much as what does. That may sound bizarre, but think about an Alfred Hitchcock movie. You are riveted by a scene where absolutely nothing is happening, because you are expecting the killer to pounce at any second. Or think about a man who lives by the train tracks and wakes up with a start when the train doesn’t come by on time.
In fact, studies show that your brain responds to the things that don’t happen, as well as those that do. If we expect to see something and it doesn’t appear, the visual part of our brain responds. That makes sense for adults, with all our massive accumulated learning and experience. But how about those baby sponges?
In a new paper in the Proceedings of the National Academy of Sciences, Richard Aslin of the University of Rochester and colleagues report on a new study of 6-month-old babies’ brain activity. They used a technique called NIRS, or Near Infrared Spectrometry. It records whether the brain is active in the occipital area, where visual pictures are processed, or in the temporal area, where sounds go.
In a control experiment, babies just heard a honking sound or saw a cartoon face emerge on a screen. Sure enough, the visual area lit up when the babies saw the face but not when they heard the sound.
Then, with another group of babies, the experimenters repeatedly played the honk and showed the image of the face right afterward. The babies started to predict that the face would show up when they heard the sound.
That’s when the experimenters arranged for something unexpected to happen: The babies heard the honking sound, but the face did not then appear.
If the babies were just sponges, nothing special should happen in their brains; after all, nothing had happened in the outside world. But if they were using predictive coding, they should respond to the unexpected event. And that’s what happened—the visual area lit up when the babies didn’t see the picture they had expected. In fact, it activated just as much as when the babies actually did see the picture.
In this way, the babies were more like scientists than like sponges. Even 6-month-olds, who can’t crawl or babble yet, can make predictions and register whether the predictions come true, as the predictive coding picture would suggest.
It turns out that baby brains are always on the lookout for the curious incident of the dog who did nothing. Each one is a little Sherlock Holmes in the making.
Source: Babies Make Predictions, Too
Via: Google Alert for Neuroscience