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Into the minds of babes
Into the minds of babes Studies of psychoactive stimulants and consciousness can shine a light on how we viewed the world as an infant, finds Anil Ananthaswamy
W
HAT is it like to be a bat? Philosophers of consciousness love toying with that question. We’re fascinated by the possibility of minds so unlike our own. But there’s a deep mystery far closer to home. Never mind bats – we barely even know what it’s like to be a baby. We’ve all been there, but none of us remember. As we develop into fully self-aware beings, our subjective experience of the world shifts dramatically. Once we leave infanthood behind, that early window on the world – and what it’s like to look through it – is closed to us. But research is prising open the shutters. As we learn more about how drugs can alter our consciousness, we’re learning more about how our brain states relate to subjective experiences. And that’s giving tantalising glimpses into our infancy. For those who want to get inside a baby’s head, Alison Gopnik, a psychologist at the University of California, Berkeley, has a few suggestions: go to Paris, fall in love, smoke four packs of Gauloises cigarettes and down four double espressos. “Which is a fantastic state to be in, but it does mean you wake up at 3 o’clock in the morning crying,” she told a room of philosophers and neuroscientists at the Toward a Science of Consciousness meeting in Tucson, Arizona, in April. And if that wasn’t enough, Gopnik adds another ingredient to the list: psychedelic drugs. Because a baby’s world might be vivid beyond adult imagination. To get a handle on the infant state of mind, we first need to know what goes on in the 40 | NewScientist | 23 August 2014
brains of adults – then see how it differs in babies. Fortunately, consciousness seems to have a telltale signature. A team led by Stanislas Dehaene of the French National Institute of Health and Medical Research in Gif-sur-Yvette has found that adult conscious perception of stimuli involves a two-stage process. The first stage involves unconscious processing of, say, an image. If we look long or hard enough, then after about 300 milliseconds, the second stage kicks in, and a network of brain regions starts reverberating. The activity correlates with conscious perception: people are able to
“A baby’s world might be vivid beyond adult imagination” report on what they have seen. It is only when this network of frontal and parietal brain regions, dubbed the global neuronal workspace, becomes active that we have conscious access to information about what we have perceived. Last year, Dehaene and his colleagues teamed up with Sid Kouider of the Ecole Normale Supérieure in Paris, France, to look for a similar signature in babies who were between 5 and 15 months old. In the first study of its kind, the team spotted clear signs of conscious perception. But there was one important difference. In babies from 12 to 15 months old, the second stage of reverberating neural activity began about 750 milliseconds after the onset of stimulus, rather than after
300 milliseconds. And in 5-month-olds, the lag was even greater. Their brains responded after 900 milliseconds. “Babies have the same mechanism, but are just slower,” says Kouider. So, babies are aware of their environment, but, compared with adults, there’s a lag. The slower reaction could be down to the prefrontal cortex, a hub for brain activity that the studies looked at. “It allows the sharing and transmission of information throughout different regions of the brain,” says Kouider. And it is one of the last brain regions to mature, becoming fully developed only in late adolescence. Another slowing factor might be down to the connections between distant brain regions. In infants, the long-distance axons that carry signals in the brain don’t yet have a fully formed coating of insulation called a myelin sheath. This means signals travel more slowly along the axons than they do in adults. But there’s more to the story. Kouider and Dehaene are investigating something called access consciousness – being aware enough of a stimulus to reflect on it and talk about it. Access consciousness is widely studied because researchers typically depend on subjects being able to monitor and report their experience. But some think access consciousness is just one extreme of a spectrum. Is there middle ground between being fully aware and fully unaware? Gopnik thinks so. And that is where babies find themselves, she says. Philosopher Ned Block of New York University has a term for this middle ground. He calls it phenomenal consciousness – what >
rebecca green
23 August 2014 | NewScientist | 41
“When we pay attention, we regress a little part of our brain to childhood” highlighted, so they paid attention to that row more than others. But having recalled a letter from the row, they were then asked to estimate the diversity of colours either in that row or in one of the others. Bronfman found that people were just as good at estimating colour diversity for the rows that had not been the focus of attention as they were for the ones that had. For some, this is clear evidence that there’s more to conscious awareness than access consciousness – which would only account for the ability to recall individual letters. Working with Tim Sweeny at the University of Denver in Colorado and his colleagues, Gopnik carried out a similar test with infants. They found that infants, like adults, are able to make judgements about a collection of objects without focusing on any particular one. The team showed cartoon images of two trees, each with oranges of varying sizes, to children aged 4 and 5. The children then played a game in which they had to help a hungry monkey pick the tree with the largest oranges. They chose correctly more often when comparing groups of oranges than when comparing individuals. So young children are good at making judgements about groups. But they are less good at focusing attention on particulars. If adult awareness is like a spotlight that lets us pay selective attention to things, an infant’s awareness is like a lantern, shedding diffuse light on everything around, says Gopnik. That may let them perceive many things at once. The upshot for Gopnik is that, instead of 42 | NewScientist | 23 August 2014
paying attention to individual things, a baby is probably picking up patterns in the bombardment of stimuli. And because they are less able to control their attention, babies are drawn to things that are rich in information. For an adult, an infant’s play area can be a cacophony of colour and sound. A baby, however, is in its element. This inability to control attention probably also means that babies are bad at shutting things out. Take a deafening pneumatic drill that has been hammering away outside your window all morning. Block notes that adults can tune out. If you’re focusing on something else, for example, you may suddenly notice the drill only at midday. A baby, though, is likely to find it hard to shut out the noise to begin with. As an infant, the world may be bright and brash, with no dimmer switch. Which brings us to the bustle of Paris, being in love, and buzzing on coffee and cigarettes. The differences between our adult experiences of the world and those of our lost early years are down to changes in the brain. But even as adults, our brains remain relatively plastic. As our attention shifts, our pliable brains shift with it, so perhaps there are ways to roll back the years, at least temporarily. Michael Merzenich at the University of California in San Francisco and his colleagues have shown that when rats are trained to pay attention either to the frequency or the intensity of sounds, their brains rearrange themselves. When the rats were paying attention to frequency, relevant neurons were Psilocybin disrupts hubs in the brain, rewinding them to when the ego was yet to emerge
doi/10.1073/pnas.1119598109
it’s like to have a subjective experience such as seeing, hearing, tasting, smelling or touching something. Take vision. For Block, when we observe a complex scene, we are conscious of a lot more than we can put into words. Of course, subjective experience is a slippery fish to study. But Block points to a new experiment that backs up his ideas. Zohar Bronfman of Tel Aviv University in Israel and his colleagues devised a test to unpick these layers of awareness. They showed subjects grids with letters in varying ranges of colours. At the start of the test, the researchers highlighted one row of letters before displaying the entire grid for 300 milliseconds. The participants were told their task was to recall a letter from the row that had been
recruited to the task – but no changes were seen in nearby neurons involved with processing intensity. And vice versa. It turns out that coffee and cigarettes can drive similar changes. The activation of certain parts of the brain for focused attention is managed by the neurotransmitter acetylcholine, which is mimicked by nicotine. At the same time, inhibitory neurotransmitters should work to stop other areas from joining the party. Unless you are drinking coffee, that is, because caffeine is thought to keep the effects of such killjoy neurotransmitters at bay, keeping your brain alert to anything and everything. By smoking and drinking coffee you nudge your brain into a state where you’re paying lots of attention – but in a wide-eyed, indiscriminate way. Being in love and travelling to new places seem to have a similar effect, says Gopnik. Under these influences, we get a more pliable, plastic brain. And that’s a fair approximation of what’s happening with babies, whose immature brains are more plastic overall. Being a baby is like paying attention with most of our brain. “As adults, when we pay attention, we are regressing a little part of our brain to its childhood state,” says Gopnik. “We are taking a little part of us and turning that into a 2-year-old again.” Gopnik has another analogy to help us get inside the head of our infant self. Think what it’s like to be totally immersed in an engrossing movie. “You are not in control, your consciousness is not planning, your self
In fact, we may start life without recognisable self-awareness at all. Instead, a baby’s sense of self is mixed up with its awareness of other people. That means babies may feel their own emotions and the emotions of others, without being able to tell them apart. “When the baby is having an experience, it is probably richer and much more intense, emotionally and subjectively,” says Kouider.
Adults are better than young children at focusing attention and shutting out distractions
seems to disappear – that’s part of what’s great about being absorbed in a movie,” she says. “Yet the events in the movie are very, very vivid in your awareness.” Being a baby might be like being sucked into a really good movie. It gets stranger. In infants, this expansive, along-for-the-ride experience of the world may go beyond perception. Kouider is not convinced by Block’s and Gopnik’s ideas about phenomenal consciousness – for him there is little to hold onto once you let go of access consciousness. But he does think that infants have a very different sense of self.
How does a baby feel the emotions of others? Probably through imitation. Smile at a baby and it smiles back. The very act of smiling is thought to induce happiness, so by imitating us, the baby feels emotions associated with those actions. The same might happen for other actions like waving or clapping. According to Kouider, we all had to figure out the boundary between ourselves and other people through social interactions. A baby learns to distinguish its own emotions from those of others by realising that it can control its own emotional state and behaviour but not that of its parents, for example. The idea that infants might be experiencing an unbounded sense of self finds support from an unlikely source: magic mushrooms. And this also gives us another way to mimic infant consciousness. Robin Carhart-Harris of Imperial College London and his colleagues have been studying the effects of psilocybin – the active ingredient in psychedelic mushrooms – on states of consciousness. They looked at the network that connects regions in the prefrontal cortex, the cingulate cortex and the temporal lobes, among others. Previous studies have shown that this “default mode network” is active when we are
Babies’ brains show the hallmarks of adult awareness, but there’s a lag
Aaron MCcoy/Getty images
Frank Rothe/getty images
Magical childhood
“The psychedelic state offers a window into what infant consciousness is like” resting and when we are thinking about ourselves, and suppressed when we concentrate on a task. Carhart-Harris’s team showed that psilocybin deactivates hubs in the brain like the posterior cingulate cortex and medial prefrontal cortex, as well as reducing long-range connectivity between brain regions. These hubs are like conductors of an orchestra, says Carhart-Harris. Bring on psilocybin and the conductors leave the room. The resulting dissonance has a striking effect, disrupting our self-awareness. “It was quite difficult at times to know where I ended and where I melted into everything around me,” said one of the volunteers in CarhartHarris’s study. These findings fit neatly with research that shows that the parts of the brain responsible for self-awareness are underdeveloped in infants. According to Carhart-Harris, psilocybin seems to rewind parts of the brain to when they were less organised and the ego was yet to emerge. “One of the reasons why the psychedelic state is so interesting is that it offers a window into what infantile consciousness is like,” he says. “It’s the brain and mind moving back to an earlier stage, essentially, where our style of cognition is less constrained, less analytical, and more influenced by imagination and wishes, but also fears.” Psilocybin also makes us emotionally volatile. Carhart-Harris is often struck by the child-like behaviour of his subjects. “One of the really notable things that you see with psychedelics is that people start to giggle,” he says. “People behave in a very silly, immature way. It’s quite endearing. They seem quite vulnerable.” Carhart-Harris’s work on psychedelics has prompted Gopnik to rethink what it’s like to be a baby. Being strung out on coffee and cigarettes may not be quite enough to explain just how bizarre infant consciousness might be. “It may be even weirder than that,” she says. It might be like being on LSD, an even more powerful psychedelic than psilocybin. Gopnik now alerts audiences to the dangers of revisiting their past. “LSD is dangerous, nicotine is very dangerous and nothing is more dangerous than falling in love,” she says. “So tea with toddlers is really the safest way to expand your consciousness.” n Anil Ananthaswamy is a consultant for New Scientist 23 August 2014 | NewScientist | 43
W
HAT is it like to be a bat? Philosophers of consciousness love toying with that question. We’re fascinated by the possibility of minds so unlike our own. But there’s a deep mystery far closer to home. Never mind bats – we barely even know what it’s like to be a baby. We’ve all been there, but none of us remember. As we develop into fully self-aware beings, our subjective experience of the world shifts dramatically. Once we leave infanthood behind, that early window on the world – and what it’s like to look through it – is closed to us. But research is prising open the shutters. As we learn more about how drugs can alter our consciousness, we’re learning more about how our brain states relate to subjective experiences. And that’s giving tantalising glimpses into our infancy. For those who want to get inside a baby’s head, Alison Gopnik, a psychologist at the University of California, Berkeley, has a few suggestions: go to Paris, fall in love, smoke four packs of Gauloises cigarettes and down four double espressos. “Which is a fantastic state to be in, but it does mean you wake up at 3 o’clock in the morning crying,” she told a room of philosophers and neuroscientists at the Toward a Science of Consciousness meeting in Tucson, Arizona, in April. And if that wasn’t enough, Gopnik adds another ingredient to the list: psychedelic drugs. Because a baby’s world might be vivid beyond adult imagination. To get a handle on the infant state of mind, we first need to know what goes on in the 40 | NewScientist | 23 August 2014
brains of adults – then see how it differs in babies. Fortunately, consciousness seems to have a telltale signature. A team led by Stanislas Dehaene of the French National Institute of Health and Medical Research in Gif-sur-Yvette has found that adult conscious perception of stimuli involves a two-stage process. The first stage involves unconscious processing of, say, an image. If we look long or hard enough, then after about 300 milliseconds, the second stage kicks in, and a network of brain regions starts reverberating. The activity correlates with conscious perception: people are able to
“A baby’s world might be vivid beyond adult imagination” report on what they have seen. It is only when this network of frontal and parietal brain regions, dubbed the global neuronal workspace, becomes active that we have conscious access to information about what we have perceived. Last year, Dehaene and his colleagues teamed up with Sid Kouider of the Ecole Normale Supérieure in Paris, France, to look for a similar signature in babies who were between 5 and 15 months old. In the first study of its kind, the team spotted clear signs of conscious perception. But there was one important difference. In babies from 12 to 15 months old, the second stage of reverberating neural activity began about 750 milliseconds after the onset of stimulus, rather than after
300 milliseconds. And in 5-month-olds, the lag was even greater. Their brains responded after 900 milliseconds. “Babies have the same mechanism, but are just slower,” says Kouider. So, babies are aware of their environment, but, compared with adults, there’s a lag. The slower reaction could be down to the prefrontal cortex, a hub for brain activity that the studies looked at. “It allows the sharing and transmission of information throughout different regions of the brain,” says Kouider. And it is one of the last brain regions to mature, becoming fully developed only in late adolescence. Another slowing factor might be down to the connections between distant brain regions. In infants, the long-distance axons that carry signals in the brain don’t yet have a fully formed coating of insulation called a myelin sheath. This means signals travel more slowly along the axons than they do in adults. But there’s more to the story. Kouider and Dehaene are investigating something called access consciousness – being aware enough of a stimulus to reflect on it and talk about it. Access consciousness is widely studied because researchers typically depend on subjects being able to monitor and report their experience. But some think access consciousness is just one extreme of a spectrum. Is there middle ground between being fully aware and fully unaware? Gopnik thinks so. And that is where babies find themselves, she says. Philosopher Ned Block of New York University has a term for this middle ground. He calls it phenomenal consciousness – what >
rebecca green
23 August 2014 | NewScientist | 41
“When we pay attention, we regress a little part of our brain to childhood” highlighted, so they paid attention to that row more than others. But having recalled a letter from the row, they were then asked to estimate the diversity of colours either in that row or in one of the others. Bronfman found that people were just as good at estimating colour diversity for the rows that had not been the focus of attention as they were for the ones that had. For some, this is clear evidence that there’s more to conscious awareness than access consciousness – which would only account for the ability to recall individual letters. Working with Tim Sweeny at the University of Denver in Colorado and his colleagues, Gopnik carried out a similar test with infants. They found that infants, like adults, are able to make judgements about a collection of objects without focusing on any particular one. The team showed cartoon images of two trees, each with oranges of varying sizes, to children aged 4 and 5. The children then played a game in which they had to help a hungry monkey pick the tree with the largest oranges. They chose correctly more often when comparing groups of oranges than when comparing individuals. So young children are good at making judgements about groups. But they are less good at focusing attention on particulars. If adult awareness is like a spotlight that lets us pay selective attention to things, an infant’s awareness is like a lantern, shedding diffuse light on everything around, says Gopnik. That may let them perceive many things at once. The upshot for Gopnik is that, instead of 42 | NewScientist | 23 August 2014
paying attention to individual things, a baby is probably picking up patterns in the bombardment of stimuli. And because they are less able to control their attention, babies are drawn to things that are rich in information. For an adult, an infant’s play area can be a cacophony of colour and sound. A baby, however, is in its element. This inability to control attention probably also means that babies are bad at shutting things out. Take a deafening pneumatic drill that has been hammering away outside your window all morning. Block notes that adults can tune out. If you’re focusing on something else, for example, you may suddenly notice the drill only at midday. A baby, though, is likely to find it hard to shut out the noise to begin with. As an infant, the world may be bright and brash, with no dimmer switch. Which brings us to the bustle of Paris, being in love, and buzzing on coffee and cigarettes. The differences between our adult experiences of the world and those of our lost early years are down to changes in the brain. But even as adults, our brains remain relatively plastic. As our attention shifts, our pliable brains shift with it, so perhaps there are ways to roll back the years, at least temporarily. Michael Merzenich at the University of California in San Francisco and his colleagues have shown that when rats are trained to pay attention either to the frequency or the intensity of sounds, their brains rearrange themselves. When the rats were paying attention to frequency, relevant neurons were Psilocybin disrupts hubs in the brain, rewinding them to when the ego was yet to emerge
doi/10.1073/pnas.1119598109
it’s like to have a subjective experience such as seeing, hearing, tasting, smelling or touching something. Take vision. For Block, when we observe a complex scene, we are conscious of a lot more than we can put into words. Of course, subjective experience is a slippery fish to study. But Block points to a new experiment that backs up his ideas. Zohar Bronfman of Tel Aviv University in Israel and his colleagues devised a test to unpick these layers of awareness. They showed subjects grids with letters in varying ranges of colours. At the start of the test, the researchers highlighted one row of letters before displaying the entire grid for 300 milliseconds. The participants were told their task was to recall a letter from the row that had been
recruited to the task – but no changes were seen in nearby neurons involved with processing intensity. And vice versa. It turns out that coffee and cigarettes can drive similar changes. The activation of certain parts of the brain for focused attention is managed by the neurotransmitter acetylcholine, which is mimicked by nicotine. At the same time, inhibitory neurotransmitters should work to stop other areas from joining the party. Unless you are drinking coffee, that is, because caffeine is thought to keep the effects of such killjoy neurotransmitters at bay, keeping your brain alert to anything and everything. By smoking and drinking coffee you nudge your brain into a state where you’re paying lots of attention – but in a wide-eyed, indiscriminate way. Being in love and travelling to new places seem to have a similar effect, says Gopnik. Under these influences, we get a more pliable, plastic brain. And that’s a fair approximation of what’s happening with babies, whose immature brains are more plastic overall. Being a baby is like paying attention with most of our brain. “As adults, when we pay attention, we are regressing a little part of our brain to its childhood state,” says Gopnik. “We are taking a little part of us and turning that into a 2-year-old again.” Gopnik has another analogy to help us get inside the head of our infant self. Think what it’s like to be totally immersed in an engrossing movie. “You are not in control, your consciousness is not planning, your self
In fact, we may start life without recognisable self-awareness at all. Instead, a baby’s sense of self is mixed up with its awareness of other people. That means babies may feel their own emotions and the emotions of others, without being able to tell them apart. “When the baby is having an experience, it is probably richer and much more intense, emotionally and subjectively,” says Kouider.
Adults are better than young children at focusing attention and shutting out distractions
seems to disappear – that’s part of what’s great about being absorbed in a movie,” she says. “Yet the events in the movie are very, very vivid in your awareness.” Being a baby might be like being sucked into a really good movie. It gets stranger. In infants, this expansive, along-for-the-ride experience of the world may go beyond perception. Kouider is not convinced by Block’s and Gopnik’s ideas about phenomenal consciousness – for him there is little to hold onto once you let go of access consciousness. But he does think that infants have a very different sense of self.
How does a baby feel the emotions of others? Probably through imitation. Smile at a baby and it smiles back. The very act of smiling is thought to induce happiness, so by imitating us, the baby feels emotions associated with those actions. The same might happen for other actions like waving or clapping. According to Kouider, we all had to figure out the boundary between ourselves and other people through social interactions. A baby learns to distinguish its own emotions from those of others by realising that it can control its own emotional state and behaviour but not that of its parents, for example. The idea that infants might be experiencing an unbounded sense of self finds support from an unlikely source: magic mushrooms. And this also gives us another way to mimic infant consciousness. Robin Carhart-Harris of Imperial College London and his colleagues have been studying the effects of psilocybin – the active ingredient in psychedelic mushrooms – on states of consciousness. They looked at the network that connects regions in the prefrontal cortex, the cingulate cortex and the temporal lobes, among others. Previous studies have shown that this “default mode network” is active when we are
Babies’ brains show the hallmarks of adult awareness, but there’s a lag
Aaron MCcoy/Getty images
Frank Rothe/getty images
Magical childhood
“The psychedelic state offers a window into what infant consciousness is like” resting and when we are thinking about ourselves, and suppressed when we concentrate on a task. Carhart-Harris’s team showed that psilocybin deactivates hubs in the brain like the posterior cingulate cortex and medial prefrontal cortex, as well as reducing long-range connectivity between brain regions. These hubs are like conductors of an orchestra, says Carhart-Harris. Bring on psilocybin and the conductors leave the room. The resulting dissonance has a striking effect, disrupting our self-awareness. “It was quite difficult at times to know where I ended and where I melted into everything around me,” said one of the volunteers in CarhartHarris’s study. These findings fit neatly with research that shows that the parts of the brain responsible for self-awareness are underdeveloped in infants. According to Carhart-Harris, psilocybin seems to rewind parts of the brain to when they were less organised and the ego was yet to emerge. “One of the reasons why the psychedelic state is so interesting is that it offers a window into what infantile consciousness is like,” he says. “It’s the brain and mind moving back to an earlier stage, essentially, where our style of cognition is less constrained, less analytical, and more influenced by imagination and wishes, but also fears.” Psilocybin also makes us emotionally volatile. Carhart-Harris is often struck by the child-like behaviour of his subjects. “One of the really notable things that you see with psychedelics is that people start to giggle,” he says. “People behave in a very silly, immature way. It’s quite endearing. They seem quite vulnerable.” Carhart-Harris’s work on psychedelics has prompted Gopnik to rethink what it’s like to be a baby. Being strung out on coffee and cigarettes may not be quite enough to explain just how bizarre infant consciousness might be. “It may be even weirder than that,” she says. It might be like being on LSD, an even more powerful psychedelic than psilocybin. Gopnik now alerts audiences to the dangers of revisiting their past. “LSD is dangerous, nicotine is very dangerous and nothing is more dangerous than falling in love,” she says. “So tea with toddlers is really the safest way to expand your consciousness.” n Anil Ananthaswamy is a consultant for New Scientist 23 August 2014 | NewScientist | 43