Archaic Reflexes

Most pages hand you a list to memorize. We're going to do something different: show you that every reflex is wired to a specific sense, and that it served to wire your movement long before you could walk.

Hello to you, movement professional,

The topic of primitive reflexes is a minefield, and let's say so right away. On one side, medical fact sheets that list them like a catalog of newborn curiosities. On the other, a whole market promising to "integrate" these reflexes with a few standardized exercises to cure attention disorder, dyslexia, or back pain. That market is called out, rightly, by scientific authorities. Wikipedia itself, at the top of the results, warns against these practices.

So we're going to take the opposite tack on both. Not a catalog, not a promise of a cure. A framework. Our thesis fits in one sentence: every primitive reflex is wired to a specific sensory system, and its role, during your development, was to calibrate your sensory-motor loop before your cortex took over. So reading a lingering reflex means spotting which sense hasn't finished its wiring work. And that, nobody tells you.

What a primitive reflex is, and why "primitive" doesn't mean "useless"

A primitive reflex, also called an archaic reflex, is an automatic, stereotyped motor response, triggered by a specific stimulus, and driven not by your cortex but by your brainstem. You present the stimulus, the response comes, always the same, with no thought and no decision. This is the very definition of the reflex arc that Charles Sherrington laid down more than a century ago: a sensory signal goes in, a motor pattern comes out.

These reflexes appear in utero and in the first months of life, and the doctor checks for them systematically at birth, because their presence signals healthy development of the nervous system. They are classically credited with four broad functions in the baby: protection, nutrition, locomotion, and coordination. The sucking reflex lets the baby feed, the grasp reflex lets it hold on, the Moro reflex lets it react to a fall, and the automatic walking reflex lets it sketch out a step.

The word "primitive" is misleading. It doesn't mean "underdeveloped and useless, an evolutionary relic to be discarded." It means "first, foundational." These reflexes are the very first motor programs of your existence, and they play a far deeper role than making you suckle. To understand it, we first need to see how a reflex differs from an adult movement.

A reflex is the rough draft of the full loop

Here's the distinction that grounds our whole reading. An adult voluntary movement runs through what we call the sensory-motor loop: a long loop that climbs all the way to the cortex, folds in the context, the history of the movement, and above all a prediction of what's about to happen. The brain predicts the expected sensory state, the body executes, and the sensory feedback confirms or corrects. It's slow to describe, but wildly rich.

A primitive reflex, by contrast, is a short loop. The sensory signal reaches the brainstem and immediately triggers its motor response, in a few tens of milliseconds, with no cortical deliberation. It's fast, reliable, and completely rigid. You can think of it as the rough draft of the full loop: a first version wired at the factory, linking a sensory input to a motor output in a raw way, until the cortex learns to do better.

And this is exactly where the whole developmental point plays out. This draft works as scaffolding, designed to come down once the structure stands on its own. To understand why, we need to look at what these reflexes actually build during the first months.

The ontogenetic goal: calibrate the loop before the cortex takes over

Ask yourself the question nobody asks: why did nature program these reflexes if they're meant to disappear? The answer is their ontogenetic goal, meaning their role in the development of the individual. Each reflex is a base pattern, a ready-made movement that prepares a voluntary skill that will follow it.

The asymmetrical tonic neck reflex (ATNR) automatically turns the arm to the side the head is facing: it wires eye-hand coordination, and it teaches the baby to cross the midline of the body. The symmetrical tonic neck reflex (STNR) couples the head to the trunk: it acts as a bridge between the moment the child creeps on the belly and the moment they hold themselves on all fours. The tonic labyrinthine reflex (TLR) organizes the body's tone according to the position of the head: it lays the foundations for righting against gravity. Each time, the reflex loops a sense and a movement together, over and over, until the wiring holds.

That's what calibrating the sensory-motor loop means. The reflex forces the repetition of a pairing between a sensory input and a motor output, which sculpts the circuits, myelinates the pathways, builds the body schema. Then, as the cortex matures, it gradually inhibits the reflex, brings it under its supervision. The neurologist Hughlings Jackson described a hierarchy in which the higher levels of the nervous system inhibit the lower ones; the release of that inhibition, through injury or immaturity, is what he called dissolution. Put simply, the cortex learns to say no to the brainstem, and that no is the birth of voluntary movement. The reflex, for its part, simply hands off to the cortex. What remains is to understand which sense, exactly, each reflex trained.

Every reflex is wired to a sense: the heart of the RNP reading

Here's the idea that changes everything. A primitive reflex is never triggered "at random." It responds to a specific sensory stimulus, and so it trains a specific sensory system. The Moro reflex responds mainly to a sudden loss of head support: its dominant input is vestibular. The asymmetrical tonic neck reflex (ATNR) responds to head rotation: its trigger is first proprioceptive, at the neck, but since turning the head also brings the inner ear into play, the vestibular system takes part. The neck triggers, the vestibular system goes along, and we keep both in the reading. The Galant reflex responds to a light brush of the skin along the lumbar spine: that's tactile. The sucking and grasp reflexes respond to touch of the mouth and palm.

A methodological clarification is in order, because this is where people go wrong most: a reflex's sense is its triggering stimulus, not the whole set of systems that fire when it occurs. The Galant reflex illustrates this well. A simple brush of the skin on the lower back triggers a curving of the entire trunk: the response is postural and massive, but the trigger itself stays purely tactile. That trigger is what we read, because it's what points to the sensory input to recalibrate.

This correspondence, reflex to sense, is the keystone of our approach. Because if a reflex trained a sense during development, then a reflex that lingers into adulthood tells you which of your senses hasn't finished its wiring. The reflex becomes an indicator, an open window onto the sensory input to recalibrate. Rather than "erasing the reflex," we trace back to the sense it reveals. Here's the full map.

The primitive reflex table: list, sense, ages, and signs of persistence

Here are the main reflexes, the sense each one is wired to, its window of appearance and integration, what it prepares, and what we observe when it stays active too long. The ages are reference markers drawn from the developmental literature, not hard cutoff dates: they vary from one child and one source to the next.

Reflex	Triggering sense	Appearance	Integration	Skill prepared	If residual
Fear-paralysis	global threat	in utero	before birth	threat-response threshold	baseline anxiety, freezing
Moro	mainly vestibular (loss of head support), also sound and light	~9 weeks in utero	~4 to 6 months	alert reaction then stress regulation	hypervigilance, startles, chronic stress
Sucking, rooting	oral and perioral tactile	birth	~3 to 4 months	feeding, oral exploration	oral habits, immature swallowing
Grasp (palmar)	palm tactile	birth	~4 to 6 months	voluntary grasping	immature grip, shoulder tension
Galant (spinal)	tactile (lumbar skin)	birth	~3 to 9 months	pelvic mobility, creeping	fidgeting when seated, bed-wetting, asymmetry
Automatic walking	plantar tactile, weight-bearing	birth	~2 months	locomotor pattern	rarely isolated
Tonic labyrinthine (TLR)	vestibular (head position in space)	in utero	up to ~3 years	antigravity tone, orientation	disorganized postural tone, fragile balance
Asymmetrical tonic neck (ATNR)	cervical proprioception and vestibular (head rotation)	~18 weeks in utero	~6 months	eye-hand coordination, midline	labored handwriting, difficult cross-coordination
Symmetrical tonic neck (STNR)	cervical proprioception and vestibular (head flexion/extension)	~6 to 9 months	~9 to 11 months	transition from creeping to all fours	slumped sitting posture, unstable quadruped position
Babinski (plantar cutaneous)	plantar tactile	birth	~12 to 24 months	maturation of the pyramidal tract	in adults, a neurological sign to investigate
Landau, righting reactions	vestibular, proprioceptive	~3 to 4 months	remains functional	antigravity righting	unstable baseline tone

If you want the short version parents often look for, there are five newborn reflexes to know: sucking, grasp, the Moro, automatic walking, and rooting. One case deserves a clear warning: the Babinski reflex. In the infant, it's normal. In the adult, it's a neurological sign that's a matter for a doctor, not a reflex to integrate. Don't let anyone sell you a protocol for it.

Integrated or residual: the nuance that changes everything

You'll often read that reflexes "disappear" around three or six months. That's a simplification. A reflex integrates rather than disappearing. It means the cortex learns to inhibit it, to hold it in reserve: the circuit stays there, functional, but it no longer commands the movement. It's exactly like learning to stop writing in block letters without forgetting how to form a letter.

A reflex is called residual, or non-integrated, when this bringing under supervision never happened. The draft was never replaced by the final version. The brainstem keeps imposing its automatic pattern as soon as the stimulus shows up, and it interferes with the voluntary motor decision. This is where it gets concrete for you: a residual reflex is a sensory-motor loop that stays partly commanded from below instead of being modulated from above.

And the system, because it's smart, compensates. The child, then the adult, develops strategies to work around the reflex that gets in the way. These compensations often work very well on the surface, but they come at a cost: they permanently tie up resources, attentional or postural, that are no longer available for anything else. Calibrating means finally letting the original wiring finish, without adding one more compensation. But first you have to know what a non-integrated reflex really costs.

When a reflex stays: what it disrupts, from posture to performance

Start with posture, because it's the most visible. The reflexes tied to the vestibular system, like the tonic labyrinthine, and the righting reactions structure your baseline tone, that permanent postural tension on which everything else is built. When they stay disorganized, movement is built on an unstable base, and no amount of strength training really fixes the problem, because the problem isn't in the muscle.

Next comes learning. The asymmetrical tonic neck reflex (ATNR), when it persists, hampers crossing the midline: writing, reading along a line, coordinating both sides of the body become costly. A residual Moro reflex keeps up a permanent state of alert, a hypervigilance that scatters attention. The co-occurrence between retained reflexes and disorders like attention disorder or dyslexia is documented by several studies. But be rigorous, and this matters: it's a correlation, not proof of cause. The reflex is an indicator, not a culprit. No serious person will tell you that integrating a reflex cures dyslexia.

And then there's performance, the ground that interests us most. For a long time, residual reflexes were thought to be limited to struggling children. A study published in 2024 in Frontiers in Sports and Active Living overturned that idea: roughly two out of three elite French soccer players retain at least one active primitive reflex, and nearly one in four an asymmetrical tonic neck reflex (ATNR). In other words, in the high-level athlete, the residual reflex is almost the norm, far from a pathology. These athletes perform in spite of it, through compensation. Which means there's still, under the hood, a locked resource to release. It's a complete shift in perspective: from treating a disorder to unlocking a potential.

Why to be wary of "integration" promises, and what we do instead

Now, the passage this article owes you. A whole market sells "reflex integration" as a miracle recipe: a few standardized cross-pattern movements, repeated every day, and attention disorder, dyslexia, or anxiety vanish.

Our approach is the opposite, and it follows from everything above. We don't try to "integrate the reflex" with a ready-made exercise applied blindly. We use the reflex as an indicator to trace back to the sense it reveals, then we work on that sensory input. A lingering asymmetrical tonic neck reflex (ATNR) doesn't tell us "do this integration exercise." It tells us: the head input, both cervical and vestibular, and its coupling with vision, are not calibrated. That's what we rework, through head movement, vestibular work, and head-trunk stabilization. The integration of the reflex then becomes a consequence of the rewiring, never the stated goal.

It's the same logic as for proprioception or the vagus nerve: you read an output of the system, here a reflex, and you act on an input, here a sense. This framework, which links each reflex to a sensory system, to posture, and to learning, is what no one else puts on the table. And it's what lets you stay rigorous on a topic saturated with promises.

What to take away, and what no one can yet promise you

Let's recap. Primitive reflexes are the first motor programs of life, short loops driven by the brainstem. Their role was never to last: it was to calibrate your sensory-motor loop by training, sense by sense, the pairing between a sensory input and a motor response, until the cortex takes over. Each reflex is wired to a sense, and that's what makes it, in adulthood, a valuable indicator when it persists.

What no one can honestly promise you is a cure through reflex integration. Science is clear on the correlations and cautious on the causes, and so are we. What we offer you is a framework: a residual reflex tells you where to look, which sense to recalibrate, which loop to finish. Between the medical fact sheet that catalogs and the charlatan who cures everything, there's a third way, the one that reads, links, and recalibrates. It's ours.

A primitive reflex is the first written record of your movement. Even today, it tells you which sense to rebuild from the ground up.

To go further and learn the full framework, take a look at the RNP Level 01 training.

FAQ

What are primitive reflexes?

They are automatic, stereotyped motor responses of the newborn, triggered by a specific sensory stimulus and driven by the brainstem. They appear in utero and in the first months, and the doctor checks for them at birth as markers of healthy development of the nervous system.

What is the role of primitive reflexes?

Beyond their immediate functions of protection, nutrition, locomotion, and coordination, their deeper role is developmental: each reflex trains a specific sensory system and calibrates the sensory-motor loop, preparing a voluntary skill that will follow it.

By what age should a reflex integrate?

It depends on the reflex: the Moro around four to six months, the asymmetrical tonic neck reflex (ATNR) around six months, the tonic labyrinthine reflex (TLR) over several years. These ages are reference markers, variable from one child to the next, not hard cutoff dates.

How do you know if a reflex persists?

A residual reflex leaves functional signs: difficulty crossing the midline and labored handwriting for the asymmetrical tonic neck reflex (ATNR), hypervigilance and startles for the Moro, unstable posture for the vestibular reflexes. An assessment by a trained professional is still needed to conclude.

Are primitive reflexes linked to attention disorder or dyslexia?

A co-occurrence is documented between retained reflexes and certain learning disorders, but it's a correlation, not a cause-and-effect relationship. The reflex is an indicator within a complex system, and its integration is not a treatment for these disorders.

Can you "integrate" a persistent reflex?

Be wary of methods that promise miracle integration through standardized exercises; several have been called out as unfounded. The rigorous approach is to read which sensory system the reflex reveals, then recalibrate that input through movement, with integration following as a consequence.

Can an adult have residual primitive reflexes?

Yes, and it's common, including among high-level athletes: a 2024 study showed that roughly two out of three elite soccer players retained at least one active primitive reflex, and nearly one in four an asymmetrical tonic neck reflex (ATNR). In the high-performing adult, it's less a disorder than a resource locked away by compensation.

Explore the 13 primitive reflexes

Each reflex has its detailed page: what triggers it, up to what age, what it reveals when it persists, and the associated RNP reading.

• The Moro reflex
• The sucking reflex
• The cardinal points reflex (rooting)
• The grasping reflex
• The Galant reflex
• The automatic walking reflex
• The Perez reflex
• The Babkin reflex
• The asymmetrical tonic neck reflex (ATNR)
• The symmetrical tonic neck reflex (STNR)
• The tonic labyrinthine reflex (TLR)
• The Landau reflex
• The Babinski reflex