Babies Are More Aware Than Parents May Have Thought, Study Finds
Infants develop consciousness as early as 5 months of age, new research finds.
Neuroscientist Sid Kouider of the Laboratoire de Sciences Cognitives et Psycholinguistique in Paris and the Technical University of Denmark and colleagues studied brain activity to understand babies' awareness.
Adults' brains show a spike in electrical activity in sensory regions when shown a subliminal image, even though they may not consciously register that they have seen a brief image. Once the image does consciously register, there is a second soar in activity, about 300 milliseconds after the image is presented.
Kouider says this pattern illustrates visual consciousness, meaning not only does the brain respond to the image but the person actually perceives the brain's response and has a conscious experience of the image.
To identify whether babies share the same brain pattern, researchers recruited 30 5-month-olds, 29 12-month-olds and 21 15-month-olds. The babies were fitted with electrode caps to measure the brain's electrical activity through the scalp, according to Live Science.
The babies then sat on one of their parent's laps while watching a screen with a patterned image. Researchers flashed a photo of a face on the screen for a fraction of a second, ranging from 17 milliseconds to 300 milliseconds.
The babies' brain activity showed a secondary spike in neural activity, indicating consciousness just like the adults. But there was a notable difference between adults and babies in the time it took for the brain activity to show up, Kouider said. In adults, the second jump in brain activity is approximately 0.3 seconds. In 5-month-olds, this took 1.3 seconds.
"It's about four times slower, actually, in the younger infants," Kouider said.
The research showed that babies 12- to 15-month-old had a quicker response to the image when compared to the 5-month-olds. The second peak in activity for the older infants occurred around eight-tenths to nine-tenths of a second.
The delay is most likely due to the undeveloped nature of a baby's brain, Kouider said. The second phase of activity that accompanies consciousness can be attributed to the visual parts of the brain that sends information to the prefrontal cortex. This part of the brain directs and maintains attention and is crucial to consciousness. It also develops the slowest, going through major changes at about a year of age.
Babies' brains also lack a fatty substance, Myelin, which sheathes nerve fibers in the brain to act as insulation, speeding up signals from one area of the brain to another. Neural impulses rely on myelin to move quickly from the visual brain regions at the back of the brain to the prefrontal cortex as the front, which is difficult before the brain becomes fully myelinated.
The results may have broader implications for medicine, Kouider noted. The research method may be helpful to determine when babies develop a conscious experience of pain.
"Our study suggests that babies are much more conscious than we believed before, and they're probably much more conscious of pain when they experience [it]," Kouider said. Researchers might also be able to detect abnormalities in conscious experience before babies learn to talk, he added, perhaps leading to earlier diagnoses of disorders such as autism.
The researchers plan to use other stimuli, such as toys babies like, to test whether familiar objects result in quicker brain response. They also plan to test babies as young as 2 months old for consciousness.
The findings will are published in the journal Science.