Jeffrey Lawson was born prematurely in February 1985. Shortly afterward, the newborn had to undergo heart surgery without anesthesia. He remained awake throughout the procedure, given only Pavulon, a muscle relaxant, to prevent movement. He died five weeks later.
After Jeffrey Lawson’s death, his mother was told that her son had been too young to tolerate anesthesia. And the anesthesiologist had attempted to reassure her that there was no evidence premature babies felt any pain.
The Lawson family’s story, famous in pain research, was not an anomaly. Until the 1980s, surgical procedures on infants were routinely performed with little or no anesthesia. Even clear defensive reactions to painful stimuli were considered to be mere reflexes.
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But more than 20 years after Jeffrey Lawson’s operation, an international research team found evidence that the brains of newborn premature babies react to pain stimuli in a very similar way to those of adults. More specifically, the researchers observed an increased oxygen supply in parts of the cerebral cortex that were associated with conscious experience. This evidence of increased neuronal activity indicated that premature babies do indeed feel pain.
Understanding the experiences of infants has presented a challenge to science. How do we know when infants consciously experience pain, for example, or a sense of self? When it comes to reporting subjective experience, “the gold standard proof is self-report,” says Lorina Naci, a psychologist and a neuroscientist at Trinity College Dublin. But that’s not possible with babies.
Among the debates surrounding the developing mind is the question of when consciousness first emerges. And that question is tied to the scientific challenge of defining conscious experience. Various philosophical, psychological and neurobiological models have attempted to explain what it is and what underlies it. Investigating whether this phenomenon exists across early development may offer new insights and ways to assess theories of consciousness.
Many scientists now recognize multiple types of consciousness and suspect that certain forms exist earlier than others in development. That insight has helped address some issues but has left others unresolved. “The answer to the question of when children become conscious depends on what exactly is meant by consciousness,” says developmental psychologist Norbert Zmyj of TU Dortmund University in Germany.
Sensation and Sensibility
Broadly speaking, there are two camps among researchers when it comes to consciousness in early development, Naci says. Some take a strict view that consciousness emerges in early childhood and that a being is only conscious once it reaches a stage where it can demonstrate abilities such as decision-making and self-reflection.
For example, one influential idea is that a mental state becomes conscious when a thought is directed toward it. So if you see a red apple and then think, “I see a red apple,” you are conscious of this sensation because you have a higher-order thought that represents it. With that definition, consciousness only arises in the course of childhood because it requires higher thought processes.
Another type to consider is the awareness of oneself as a distinct being, which emerges around 18 months. From about that age of one and a half, most toddlers who receive a dab of paint on their cheek without noticing it will, if then placed in front of a mirror, not only recognize themselves but also touch the affected area or point it out to others. “The children obviously have an idea of themselves and compare it with their reflection,” Zmyj says. “Younger children, on the other hand, see their reflection as a play partner or touch the spot in the mirror instead of their face.”
The second camp of researchers thinks of consciousness in a broader way that includes what is sometimes called primary, or core, consciousness. That’s the awareness of the present moment and of sensations. And in that framing, consciousness could be present much earlier in life.
In a review paper published in 2023, Naci and her colleagues discussed behavioral evidence that infants experience some form of subjective sensation—or primary consciousness—shortly after birth. For example, newborns fixate on faces, contort their expression in response to pain and react to sounds in ways that indicate they distinguish their mother’s voice from that of strangers. That last ability is notable because it implies learning and would require memory, which researchers also believe is critical to certain types of consciousness.
The catch is that these examples could be explained away as automatic. Observing these behaviors is not enough to be confident about an infant’s experiences of the world. “We need better methods to study early consciousness, both to define it … and to detect it,” says neuroscientist Julia Moser of the University of Minnesota, who was a co-author of the 2023 review. To really understand conscious awareness, she and others argue, we need to look to the brain.
When Perception and Awareness Align
The relationship between consciousness and perception is complicated. As just one example, people affected by “blindsight” have sustained damage to their primary visual cortex, part of the brain’s visual system. If you ask them whether they can recognize an object in their field of vision, they answer in the negative.
But if you ask people with blindsight to guess where an object is located, in many cases, they can reach for it or at least point in the right direction. That ability suggests the brain is processing visual stimuli unconsciously, even though the person does not have the impression of seeing anything.
Many experiments involve manipulating the visibility of an object with the hopes of identifying consistent patterns in brain activity that could be markers of conscious experience. For instance, in a typical experimental setup, people view two images in such rapid succession that the second effectively “covers” the first in their perception. As a result, people do not report seeing the first image.
In the first 200 to 300 milliseconds of visual processing, however, reactions do occur in sensory areas of the brain. Much like the blindsight cases, the brain is perceiving something that the person is not consciously aware of seeing.
By tweaking these experiments, scientists have confirmed that a visual must appear for at least 300 milliseconds for people to perceive it correctly. That experience is accompanied by a synchronized, widely distributed brain response in the frontal and parietal lobes. This peak in the brain’s response, measured by tracking electrical activity known as the P300 wave, is considered a reliable indication of conscious perception.
A team of researchers based in France looked for such patterns in infants. The group included cognitive neuroscientist Stanislas Dehaene of the College of France and pediatrician Ghislaine Dehaene-Lambertz of the French National Institute of Health and Medical Research. In one study, the group used caps fitted with electrodes to record fluctuations in electrical brain activity in 80 children aged five months, 12 months or 15 months.
While wearing these caps, the young participants saw faces on a screen for different lengths of time. These images were embedded in visual patterns to make them more difficult to detect.
Using this setup, the researchers documented a slow brain wave in children aged one year and older that resembled the P300 brain response of adults—although it appeared much later than in adult participants. In five-month-old infants, the wave again appeared, albeit less pronounced and even more delayed than in the older babies.
Based on this brain activity, the team concluded, infants as young as five months could have conscious visual impressions.
Integrating Information and Imaging the Brain
Another way to explore the development of consciousness is to check for brain activity associated with this state in adulthood with functional magnetic resonance imaging (fMRI). For example, Naci and her colleagues have looked for the interplay of two brain networks: the frontoparietal and default mode networks.
The frontal and parietal regions are part of the brain’s dorsal attention and executive control networks, which support our ability to plan and work toward goals. These networks are also important to theoretical models of consciousness, such as global neuronal workspace theory. The default mode network, so named because it is active when we are not doing anything in particular, supports activities such as thinking about oneself and allowing one’s mind to wander.
In healthy adults, these areas have a complementary, coordinated relationship: one activates while the other is suppressed, and vice versa. By contrast, that back-and-forth does not play out as normal when people are under anesthesia or in a vegetative state.
In a study published in 2022, Naci and her colleagues looked at measurements of the spontaneous brain activity of newborns at rest, which allowed the scientists to record the communication between neurons in different areas of the brain. Not only did they see the frontoparietal and default mode networks; they also found that the brain regions already exhibited a pattern of complementary activation.
And in 2025 Naci and her colleagues published findings with another signature of brain activity linked to consciousness in adults. The team observed a pattern of brain connectivity associated with the efficient transfer of information called small-world architecture. They found that not only did full term newborns have this pattern of connectivity but that a majority of premature infants, born at 32 to 35 weeks, did as well—albeit in a less developed form.
Meanwhile Moser and her colleagues have designed experiments that combine imaging with a specific task to observe whether the brain’s hardware in utero is engaged in the same kinds of processes that are present in later life. Specifically, they used a method called fetal magnetoencephalography to measure brain activity in 56 healthy fetuses between the 25th and 40th week of pregnancy with sensors on the pregnant person’s abdomen.
The researchers then set up a classic experiment that was related to consciousness and involved rule violation: they played a repeating sequence of sounds, then altered this pattern to observe any changes in brain activity that might indicate awareness of that disruption. In their study, fetuses as young as 35 weeks showed changes in activity that suggest a recognition of the changed pattern. “This is, for us, a sign of this very primary, sensory form of consciousness, because basically your brain was able to cover a memory span of more than a minute,” Moser says. “Then your brain adapts its response to what has been learned.”
Other studies by researchers such as Franziska Schleger of the University of Tübingen in Germany point in a similar direction. Based on brain activity, they saw evidence that newborns and fetuses notice when the number of sounds played changes.
Still, Moser stresses that this work does not indicate that a fetus is conscious. “A lot of the things we’ve been studying are sensory awareness,” she explains. These capacities could be early pieces of what will become conscious experience.
Setting Limits on Early Consciousness
There is also a notable anatomical boundary that limits when even the earliest forms of consciousness could arise. In 2020 Hugo Lagercrantz of the Karolinska Institute in Sweden observed that consciousness can only awaken when there are connections between brain areas called the thalamus and the cerebral cortex.
The thalamus acts as a control center and transmits sensory signals to various areas of the cerebral cortex. The corresponding nerve fiber connections develop around the 24th week of pregnancy. From then on, according to Lagercrantz, consciousness is at least theoretically possible. But, he says, “I’m not sure whether a fetus is really conscious yet. Most of the time, it sleeps, even if it reacts to pain, touch and the mother’s voice.”
After birth, it is a different story, as a child’s expanded behavioral repertoire makes clear. A newborn can imitate their parents and react more strongly to human conversation than to other sounds, for instance. These can all be taken as signs of minimal consciousness.
And Lagercrantz and Moser agree that consciousness does not emerge from one moment to the next but builds gradually. According to Moser, this fits in well with our understanding of development in other areas of cognition, such as memory.
“Most abilities grow gradually, even those that have little to do with cognition, such as the ability to see accurately or control muscles,” she says. Why would consciousness be an exception?
This article originally appeared in Spektrum der Wissenschaft and was reproduced with permission.