If you’re reading this, you are probably fairly certain that you’re conscious. You likely assume that your loved ones, your less-loved ones and even your weird neighbour are all conscious too.
They look and act like you – a fellow human – so it is reasonable to think they experience the world in a similar way.
But what about tiny little babies who don’t understand the world and can’t talk to you about it? None of us remember what it was like to be that young; so, are they conscious? And what about babies that haven’t even been born yet?
These are the questions that have captured the curiosity of neuroscientists in recent years. Neuroscientist Dr Joel Frohlich describes it as a scientific “frontier.”
“There hasn’t been much research into when consciousness begins – surprisingly little,” he tells BBC Science Focus. “For a long time, consciousness was the purview of philosophers. In neuroscience, it was almost taboo to research until maybe 10 or 20 years ago.”
But now, neuroscientists have developed a few weird and wonderful ways to try to understand what it feels like to be a new- or unborn baby, and answer the question, when does consciousness start?
Searching for clusters
According to a paper by Frohlich and philosopher Professor Tim Bayne, the answer to that big question is at least as early as five months. Probably.
At that age, babies show enough evidence – not just of being awake, but of truly experiencing the world.
Their conclusion comes from what they call a “cluster-based” approach: instead of looking for one single marker of consciousness, they identify a whole set of clues – brain activity patterns, responses to stimuli, signs of awareness.
“Any one marker by itself, we shouldn’t fully trust,” says Frohlich. “But if you see a convergence of mini markers, that’s a pretty good indicator that consciousness might be arising.”
So, does that mean babies under five months aren’t conscious? Well, here’s where it gets really interesting: while younger babies don’t show all the signs of consciousness, they display some markers. And intriguingly, similar clues might be present in foetuses as well.
What are the biggest clues of consciousness?
One of the biggest markers of a conscious brain, according to neuroscientists like Frohlich, is the default mode network. This is a network of brain regions that is active when you’re at rest – when you’re daydreaming, reminiscing or thinking about the future.
Neuroscientists have discovered with the use of functional magnetic resonance imaging (MRI), a type of brain scan, that newborn babies have some simplistic form of a default mode network.
Then there’s the local-global effect. It’s fairly simple: according to Frohlich, the ability to notice when a pattern changes is a sign of working memory, and possibly consciousness.
For instance, take a look at these sequences:
- Beep-beep-beep-BEEP
- Beep-beep-beep-BEEP
- Beep-beep-beep-BEEP
- Beep-beep-beep-beep
Notice a change in the last sequence? Congrats! That could be a sign you’re conscious.
“I could train your brain, after many repetitions of this sequence pattern, to expect the final tone within this four-tone sequence to be deviant,” explains Frohlich.
“Then if I give a new sequence that breaks that pattern – it could just be four identical tones – even though there’s no local deviant within that sequence, there’s a global deviant; something that broke the pattern.”
While Frohlich has seen evidence of this local-global effect in newborn babies, other research has gone further. Researchers at the University of Tubingen, Germany, found evidence of it in late-term foetuses. They put machines over pregnant bellies to measure magnetic fields given off by foetal brain signals – a technique called magnetoencephalography.
Shining lights into wombs
Another potential marker of consciousness is behaviour and attention. Scientists can observe that young babies – at least as young as four months old, according to Frohlich and Bayne – can choose where they direct their attention.
And again, there’s some evidence that foetuses can do this too.
In a 2017 paper, Prof Vincent Reid and five other neuroscientists at the University of Lancaster shone three lights – arranged like two eyes and a mouth – into the uteruses of pregnant people and used ultrasound to measure foetuses’ reactions to it.
The neuroscientists moved these lights across the pregnancy bump and saw that foetuses would move their heads to look at them.
“Nobody really agrees if the foetus is seeing something that looks like a face or more like a smudge of light,” says Frohlich.
But, he says, a team of neuroscientists in Torino, Italy, independently replicated this experiment, tracking foetal eye movements rather than head turns, and found that the lenses of the foetuses’ eyes followed the face-like lights too.
How early might consciousness begin?
All this is to say, the various tests that neuroscientists can do suggest that young babies – and perhaps foetuses – have some level of consciousness.
But it’s time to address the elephant in the room. If consciousness begins before birth, this might raise questions about the ethics of abortion. However, Frohlich says there is no need to worry.
“What is really important to understand here is we’re only talking about the last trimester of pregnancy, which is usually after the legal limits on abortion in most jurisdictions,” he says. “The vast, vast, vast majority of abortions that take place are much earlier than that, usually in the first trimester of pregnancy.”
Any earlier than the third trimester would predate the development of part of the brain that processes sensory signals: the thalamus, nicknamed the gateway to consciousness.
“The thalamus doesn’t even establish connections – synapses – with the cerebral cortex until the beginning of the third trimester, or 24 to 26 weeks’ gestation,” says Frohlich. “Until then, there’s not really plausible consciousness – at least as we know it; filled with sensations from the outside world.”
However, the work of neuroscientists like Frohlich could have profound implications for how we decide what other entities count as conscious.
As artificial intelligence emerges and becomes increasingly sophisticated, Frohlich says it might be useful for scientists to develop a “theory of consciousness.”
“If we can say, in humans, ‘Consciousness begins at this age,’ then we could extrapolate to other systems, based on whatever criteria we use to reach that conclusion for ourselves,” he says.
Read more:
- What is consciousness?
- New ‘map of consciousness’ could help to wake up coma patients
- The mystery of your 'baby amnesia' just got even weirder
About our expert:
Dr Joel Frohlich is a postdoctoral researcher studying foetal neuroscience at the Helmholtz Centre Munich, at the University of Tübingen. His current research uses magnetoencephalography to study foetal and infant development. Besides his academic position at the University of Tübingen, Frohlich also serves as a research consultant at the Institute for Advanced Consciousness Studies in Santa Monica, California.
