Babies are aware of what's going on, not just reflexively reacting to it, scientists concluded after a series of experiments on babies as young as 5 months.
A contestant in the 2000 American Baby Derby heads towards the finish line. Crawling babies raced to see who was fastest. According to the promoters, The Boston Baby Faire, a two-day event with more than 200 exhibitors of every type of baby product, is the largest baby exposition in the United States.
John Nordell / The Christian Science Monitor
EnlargeInfants have a conscious experience of the world at as early as 5 months of age, new research finds.
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New parents may raise an eyebrow at the idea that their baby might not be a conscious being, but scientists have, until now, not been able to clearly show that infants react with awareness rather than reflexively. Even in adults, much of the brain's processing of the world occurs without conscious awareness, said Sid Kouider, a neuroscientist at the Laboratoire de Sciences Cognitives et Psycholinguistique in Paris and the Technical University of Denmark. ?
One odd phenomenon, "blindsight," occurs in people with damage to part of their visual cortex. Although they cannot consciously see, they're able to "guess" the location of a visual stimulus or even catch objects tossed at them. Blindsight reveals that even unconscious processing in the brain can result in seemingly goal-directed behavior.
So when babies look toward a face or grasp an object, they, too, might be doing so without a conscious experience of what they're seeing.
"Infants might be responding in a kind of automatic manner," Kouider told LiveScience. Unfortunately, since babies don't talk, scientists can't test consciousness by asking infants what they experience.
Baby brain patterns
So Kouider and his colleagues turned to brain activity for a peak into babies' awareness. When adults are shown a subliminal image, their brains show a spike in electrical activity in sensory regions ? even though they may not consciously register that they've seen such a brief image.
When the image does consciously register, however, the brain shows a second leap in activity, typically about 300 milliseconds after the presentation of the image. This pattern reveals visual consciousness, Kouider said, which means that not only does the brain respond to the image, but also the owner of that brain perceives that response and has a conscious experience of the image.
The researchers wanted to know whether babies would show this same brain pattern. They recruited 30 5-month-olds, 29 12-month-olds and 21 15-month-olds and fitted the babies with electrode caps that measure the brain's electrical activity through the scalp.
Next, the babies sat on their mother or father's lap while watching a screen with a patterned image. For a fraction of a second (ranging from as quick as 17 milliseconds up to 300 milliseconds), the researchers flashed a photo of a face on the screen.
Experiencing awareness
The scientists then analyzed the babies' brain activity to search for the two-phase pattern that would indicate consciousness. They found it: Babies did indeed show a secondary spike in neural activity, just like adults.
But there was one important difference between the babies' neural patterns and those seen in adults, Kouider said. In 5-month-olds, it took 1.3 seconds for the second flurry of brain activity to show up. In adults, the timing is closer to three-tenths of a second, or 0.3 seconds.
"It's about four times slower, actually, in the younger infants," Kouider said.?
Older babies show snappier processing, though still not as quick as adults, the researchers found. In 12- to 15-month-olds, the second phase is stronger than in 5-month-olds and occurs around eight-tenths to nine-tenths of a second.
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