Are babies truly conscious? The question had scientists baffled until a team in Abu Dhabi studied infants' brain activity, and found they were more aware than initially thought. That may shine light on another enigma – how the brain gives rise to consciousness. It is among the most profound concepts science can address. Daniel Bardsley reports
Pull a face at a baby, and it will react. It might smile, or burst into tears – or both, in rapid succession – but it will seem obvious that it is conscious of what is going on around it.
Yet with their emotions seeming to move from joy to tears with such speed, it is tempting to wonder whether babies act from reflex.
Indeed, turn the clock back several decades and the prevalent view was that babies were not truly aware of what was going on around them, or what was being done to them – to the extent that surgeons operated on babies without anaesthesia.
That is now rarely the case, at least in developed healthcare systems. But a definitive answer to the question of whether or not babies are actually conscious has remained tantalisingly out of reach. After all, how can you tell whether someone is conscious if they can’t speak?
You can cut out the middleman of language, and look directly at what’s going on in the brain. That is precisely what a group of researchers, led by Sid Kouider, a visiting professor at New York University Abu Dhabi, have been doing.
They showed babies of various ages – five months, 12 months and 15 months – pictures of faces very briefly, and analysed what was going on in their brains by means of 128 electrodes attached to various parts of their heads (a non-invasive procedure similar to having an electrocardiogram (ECG) measurement of electrical activity in the heart).
They showed the infants images of faces for periods ranging from as short as 17 milliseconds (ms) up to 300ms – a little less than a third of a second – and analysed graphs of the electrical response of the babies’ brains against time, known as the event-related potential (ERP).
Similar tests have been done on adults. They found that even when an adult is shown an image for such a short period of time they cannot remember seeing it – meaning they saw it only subliminally, but there is nonetheless a short linear burst of electrical activity in the brain. The brain has registered seeing the image even if the person doesn’t realise it. When an adult views an image for long enough that he or she can later recall seeing it, the ERP is different. First there is the same initial linear electrical response, but this is followed on the graph by a non-linear pattern that is different.
Prof Kouider looked at the babies’ scans to see whether they showed just the linear response – which would suggest that they weren’t truly conscious, and were acting by reflex – or the non-linear response, which would show that they were. The results, published last year in the journal Science, found the ERP for babies showed this non-linear pattern.
Younger babies tended to react more slowly than older ones, suggesting that these mechanisms of perception were still developing. Younger babies also have to be shown a face for a longer period of time before they orient their gaze to it, compared with older babies.
“In babies the neural mechanisms take longer on average [than in adults] – three to four times longer. It takes one third of a second for you to become conscious of an object. For babies it takes one second or more,” said Prof Kouider.
But while babies are slower in their responses, Prof Kouider is confident that his results do indicate they are conscious, just like adults. The study indicates an “unambiguous pattern of brain activation” associated only with consciousness, although Prof Kouider concedes that, as his research is “working by analogy”, it is impossible to be certain.
“We have some strong evidence here because we found exactly the same mechanisms [as in adults]. We’re pretty confident that what’s happening is the same thing, that they become conscious when they process that information,” he said.
Prof Kouider and his co-researchers are now delving deeper into the conscious abilities of babies in the hope of answering questions related to toddlers’ abilities to examine their thoughts and feelings.
Using similar methods of analysing brain activity, and comparing it with patterns in adults, they are looking at how babies react when objects are made available to them or when those objects are missing. Do the babies know there should be something there, and are they aware they know this? Prof Kouider expects it will take three to four years to come up with answers.
“We’re trying to understand what the content of the consciousness is. Is it richer than the content of consciousness in an adult?” he said.
Prof Kouider believes this may indeed be the case, given that infants tend to be surprised by their surroundings more often than adults, who have previously experienced most of the phenomena they come across in a typical day.
These types of studies help to address questions of how the brain gives rise to consciousness, perhaps one of the most profound concepts science can grapple with. Prof Kouider points out that in the past it was philosophers who tried to provide answers, while neuroscientists are now in the driving seat.
“We don’t fully understand how the mind emerges from the brain, but we have been making enormous progress over the past two decades,” he said. “It’s maybe the most difficult issue along with cosmology because we don’t have any idea of what are the limits.”
What is clear already is that the work of the brain that we can perceive is but a fraction of its overall activity – like the tip of an iceberg. That raises a host of fascinating questions that will probably keep researchers busy for many years to come.
“So, are we mostly unconscious most of the time, or do we need consciousness for certain purposes?” Prof Kouider asked. “What’s the function of consciousness? If there’s no function, why are we conscious?”