While adults automatically block out irrelevant information, such as the hum of an air conditioner or the conversation of nearby strangers, babies take everything in: their reality arrives without a filter. As a result, it typically takes significantly higher concentrations of anesthesia to render babies unconscious, since there's more cellular activity to silence.
The hyperabundance of thoughts in the baby brain also reflects profound differences in the ways adults and babies pay attention to the world. If attention works like a narrow spotlight in adults - a focused beam illuminating particular parts of reality - then in young kids it works more like a lantern, casting a diffuse radiance on their surroundings.
"We sometimes say that adults are better at paying attention than children," writes Gopnik. "But really we mean just the opposite. Adults are better at not paying attention. They're better at screening out everything else and restricting their consciousness to a single focus."
Consider, for instance, what happens when preschoolers are shown a photograph of someone - let's call her Jane - looking at a picture of a family. When the young children are asked questions about what Jane is paying attention to, the kids quickly agree that Jane is thinking about the people in the picture. But they also insist that she's thinking about the picture frame, and the wall behind the picture, and the chair lurking in her peripheral vision. In other words, they believe that Jane is attending to whatever she can see.