As a neuroscientist interested in consciousness and a mother of a baby, I often find myself wondering what sort of experiential world my little Max has been enjoying since he came into this world.
Having celebrated his first birthday this week, he is now taking a few wobbly steps and showing a clear personality with an insatiable love of balls and dogs (in fact “dog” is his only decipherable word so far).
Today the renowned journal Science published a new study that claims to provide the first neuroscientific evidence that babies are indeed conscious. The importance of this finding can be debated on many levels.
When does human consciousness emerge?
It’s totally unsurprising to me that 12-15 month old children have brain responses consistent with being conscious – simply because it seems inconceivable that a child of that age and behavioural repertoire could be unconscious.
When little Max screams, I never question whether he is actually experiencing pain or whether his cries are a simple automatic reaction triggering a vocal response, independent of any sensation on his part.
I suspect most readers would share my view that one-year-old babies have a conscious experience. Similarly, I imagine the majority would dispute the idea that consciousness might accompany (or even precede) the moment of fertilisation.
If you share these beliefs then the million-dollar question is: WHEN does consciousness emerge?
Does it come with a bang - after which the embryo or baby becomes conscious, when before there was nothing? Might consciousness emerge gradually from the moment of conception or a later?
If you believe it’s a gradual processes, does it continue across the lifetime with a “peak” of consciousness? Is there a similarly defined point at which maximum development of consciousness as occurred, after which point it gradually erodes away?
It’s not an accident that I’m presenting these alternatives as simple statements of belief. Readers may be interested to know that, until now, my unwavering certainty that my one-year-old baby Max is conscious had not been backed up by a single shred of scientific evidence.
Indeed, the famous philosopher Daniel Dennett still maintains it’s impossible for any of us to know for certain whether the adults – let alone the children - around us are in fact zombies that just “appear” to be conscious. Dennett is correct that we still have no way to prove with 100% certainty your friends are not zombies.
What is scientific “evidence” of consciousness?
Given it’s not possible to disprove the existence of zombies with science, it is important to first understand where the science of consciousness is in 2013.
While acknowledging there continues to be a lack of universal agreement, there is now mounting evidence that conscious experience seems to be accompanied by brain activity that is very extensive, both in duration and distribution.
The new Science paper, and many other studies attempting to identify the elusive “neural correlate of consciousness”, use a type of illusion called “masking.” This involves presenting an image briefly on a screen before replacing it with a second image or texture.
It is known that people generally report seeing the first image if the time gap between the first and second image is greater than 100 milliseconds, but they report no awareness if the gap is less than 50ms.
Things become more interesting between the 50-100ms window when people sometimes report conscious awareness and other times don’t. It is only in trials that people report awareness that neural responses to the stimuli are found to persist and extend into the areas of your brain located behind your forehead.
In cases when no conscious awareness is reported, the neural responses are only very short-lived and limited to a relatively small area of the brain dedicated to early visual processing.
In the new study, the authors show this neural signature of consciousness is seen in babies at 12-15 months of age and to a lesser extent – but still clearly visible – in babies as young as five months.
Without getting into the subtleties of the results, to me the most interesting finding in this paper is the hint that the signs of consciousness appear to be both reduced and slower in the five-month-old babies. While the authors clearly report this in the paper, they chose not to highlight it in the discussion or to draw any inferences from this finding.
In my personal communication with the study’s lead author, Dr Kouider acknowledged the results are indeed consistent with a reduced or different form of conscious experience in these five-month-old babies – something he speculated may be akin to “pre-consciousness” – a concept he has previously explored in an interesting review paper published in TICS in 2010 (this and other articles can be accessed through Dr Kouider’s homepage).
Simplistically, the idea is that basic features in the environment, such as colour and light intensity, may be experienced but without the rich and complex meaning and emotions that are central to the consciousness experiences reported by adults.
In many respects, the greatest significance of this paper is that it provides the first clear neuroscientific contribution to the debate about whether babies are conscious.
As a mother and scientist, I am waiting with genuine anticipation to read future developments on this quest to understand the inner experiences of the youngest members of our species.