Infant consciousness seems like a difficult question. It’s one people often react to with outrage that it’s even being asked. Of course they’re conscious, is the sentiment. Aren’t they human, and don’t we see them crying, showing facial expressions, and exhibiting other behaviors? Others conclude that there’s no real way to know since they can’t talk and reveal their experience to us.
For several decades in the 20th century, the medical profession largely assumed that babies were not in fact conscious. As a result, they were often subjected to medical procedures, including surgery, without anesthesia. (I was initially skeptical about the surgery part, since operating on a screaming convulsing infant, even if only driven by nociception and reflex, doesn’t seem productive, but apparently they were given muscle blockers to paralyze them.)
This started to change in the 1970s. But Frank Amthor pointed out in Neuroscience for Dummies that this didn’t appear to be due to any scientific discoveries. Claudia Passos-Ferreira, in an interview with Richard Brown, noted that part of this reflected a growing concern about the effects of nociception on the infant’s long term health.
The argument for babies not being conscious is that their behavior is dominated by reflexes. You don’t need phenomenal awareness to cry, suck, startle, or grip. This fits with the fact that the cerebral cortex in a baby remains immature, with exuberant synaptogenesis and myelination still in progress. And we all have infantile amnesia; we don’t remember the first couple of years of life.
But immaturity doesn’t mean non-functional. The cortex of an infant is less differentiated than an older human’s, and performs more slowly, but that doesn’t mean it’s not operating and influencing behavior. Infants from the beginning show a fascination with human faces, processing known to happen in particular locations in the cortex, such as the fusiform face area.
Stanislas Deheane, in Consciousness and the Brain, expresses disdain for philosophical declarations on this. He describes experiments that show infants having the same neural markers for consciousness as adults, although they manifest slower. For example, the P300 wave takes longer to evolve, 900 milliseconds in a five month old rather than the 300 milliseconds for adults.
Although Passos-Ferreira points out that by five months, we already have enough evidence for flexible and learned behavior to make the case that consciousness is present. It’s the earlier periods, notably the first month or two of life, where things are more difficult.
As usual, my take on this is that it depends on which definition of “consciousness” we’re working with. I think asking whether a baby is conscious, as though consciousness is something either present or absent, is meaningless. It’s clear babies lack some mental capabilities older humans have, but it’s also clear they still have some subset of them.
Pulling out my usual hierarchy of consciousness definitions:
- Matter: a system that is part of the environment, is affected by it, and affects it. Panpsychism.
- Reflexes and fixed action patterns: automatic reactions to stimuli. If we stipulate that these must be biologically adaptive, then this layer is equivalent to universal biopsychism.
- Perception: models of the environment built from distance senses, increasing the scope of what the reflexes are reacting to.
- Volition: selection of which reflexes to allow or inhibit based on learned predictions.
- Deliberative imagination: sensory-action scenarios, episodic memory, to enhance 4.
- Introspection: deep recursive metacognition enabling symbolic thought.
It seems clear a newborn has at least 1-3. Level 4, if not present at birth, seems to come rapidly in the first few months of life, with 5 and 6 perhaps taking longer.
So the question isn’t whether babies are conscious, but how conscious they are at various developmental stages. Which seems like a much less emotional question to ponder.
Unless of course I’m missing something?