Why is a baby's grip so strong?

Thanks to Andrew Bremner for the answer!

Andrew - Infants are born with a really wide range of different reflexes, including the stepping reflex, the moro reflex, the suck reflex, and the rooting reflex alongside the Palmer implanter grasps. And traditionally, people have argued that reflexes at birth are automatic and governed entirely by the spinal cord, with no involvement at all from the cerebral cortex in the brain.

Will - And if the grip is a reflex instead of a conscious choice, it makes sense then for there to be less quality control involved. Anyone that's had their knee hit in that one place that makes you kick isn't really in control of how hard the kick is. And if the grip is a reflex, it makes sense for it to wane as the baby becomes a bit more cogent and aware of how the world works.

Andrew - As the cerebral cortex matures and starts to exert more of a controlling role on action via the spinal cord, it starts inhibiting the strong spinal reflexes observed at birth. Eventually, neonatal reflexes are largely overlain with, or replaced by, intentional and controlled actions. So rather than demonstrating a stepping reflex, then that gradually wanes and then is replaced of course by locomotion. So crawling and eventually walking in young children.

Will - But what do more recent studies say about this theory?

Andrew - The traditional explanation of this early strength of newborn reflexes has received a bit of critique more recently. So researchers have noticed that newborn babies can behave in what looks like a controlled rather than an automatic, reflexive way. Newborns can actually move their hand to intercept a moving object, which they've seen with their eyes. And some reflexes, far from being automatic, are actually strongly affected by the infant's current state. For instance, the rooting reflex, which is involved in feeding, occurs much more when newborn babies are hungry. I think there's probably a bit of truth in both of these perspectives, the more recent one and the traditional one. So newborn reflexes are likely not entirely automatic. So we know from neuroscience research that the cerebral cortex is functioning and plays a role in movement early in development. But perhaps this is a matter of degree and probably the inhibiting role of the brain in moderating strong and more automatic spinal reflexes is not fully developed yet at birth. So we don't have a cut and dry answer to the question of why newborn reflexes like the palmar grasp are so strong, but I suspect that it's because they're more automatic and less controlled than they are later in development.

Will - Perhaps a bit of both then. Thank you to Paris for the question, and to Andrew Bremner for the answer.