The asymmetric tonic neck reflex, or ATNR, is one of several primitive reflexes that emerge during fetal life and serve an infant’s earliest survival and motor needs. In a healthy infant, the ATNR is present at birth and gradually disappears within the first several months as the brain matures. When it does not disappear on schedule, the lingering reflex can interfere with voluntary movement, hand-eye coordination, and aspects of learning that depend on those motor foundations. Understanding what the reflex looks like, why it sometimes persists, and what can be done about it is more nuanced than many popular parenting resources suggest.
What the ATNR Is and When It Should Disappear
When a newborn’s head turns to one side, the ATNR causes the arm and leg on that side to extend while the limbs on the opposite side flex. The posture resembles a fencing stance, which is why some clinicians call it the “fencer’s reflex.” This involuntary pattern is not a defect. It plays a role in early motor learning, helping the infant discover their own hands and develop the initial coordination between head turning and arm reaching. The reflex also appears to facilitate passage through the birth canal and may support early feeding by orienting the head and body together.
Primitive reflexes like the ATNR are driven by lower brain structures, particularly the brainstem. As the cerebral cortex matures during the first months of life, higher-level postural reactions gradually replace these automatic patterns. The ATNR typically fades between about three and six months of age, though the exact window varies. If the brain’s maturation proceeds normally, voluntary motor control overrides the reflex, and the infant can eventually turn their head without triggering involuntary limb movements. When that override does not happen, clinicians describe the reflex as “retained” or “persistent.”1Europe PMC. Tonic Neck Reflex
Signs of a Retained ATNR
A retained ATNR does not usually look like the dramatic fencing posture of a newborn. In older children and adults, the effects are subtler. Because the reflex links head turning to limb extension, it can quietly disrupt any activity that requires the head and hands to work independently. The telltale signs tend to cluster around motor coordination, writing, and balance.
In school-aged children, retained ATNR commonly shows up as:
- Messy handwriting: When the child looks down at the page and turns their head even slightly, the writing hand may involuntarily tighten or extend, making smooth pen control difficult.
- Trouble crossing the midline: Activities that require one hand to reach across the center of the body feel awkward. The child may rotate their entire trunk instead of just moving an arm.
- Poor balance: Head movements trigger subtle shifts in muscle tone through the limbs, which makes tasks like riding a bike or catching a ball harder than they should be.
- Difficulty tracking with the eyes: Reading requires smooth eye tracking from left to right while the head stays relatively still. A persistent ATNR can make the eyes and head compete for control, leading to lost place on the page, skipped lines, or slow reading speed.
- Awkward sports performance: Any sport where the eyes and head need to track a moving object while the hands do something different becomes disproportionately challenging.
A persistent primitive reflex can also interfere with cognitive processing and emotional regulation, not just physical coordination.2The Journal for Nurse Practitioners. Persistent Primitive Reflex and Developmental Delay in the School-Aged Child Children who struggle with writing or reading because of a retained reflex often develop frustration and avoidance behaviors that can be mistaken for laziness or attitude problems. The motor difficulty is invisible to most teachers and parents, so the child’s struggle gets attributed to effort rather than neurology.
How Retained ATNR Connects to Reading and Attention
Some of the strongest research linking retained ATNR to functional problems comes from studies of children with reading difficulties. One study of primary-school children found that those in the lowest reading group had substantially higher levels of ATNR persistence compared with average and above-average readers. About 17% of children in the lowest reading group showed extremely high ATNR levels, while none of the children in the middle or top reading groups did. In the better-reading groups, roughly two-thirds of children showed no detectable ATNR at all.3PubMed. Prevalence of persistent primary reflexes and motor problems in children with reading difficulties That is a striking gap, though the researchers emphasized that persistent ATNR should not be treated as a causal explanation for reading difficulties like dyslexia. The association is real, but the direction of causation is not settled.
A separate study of children with dyslexia found that about two-thirds of them had retained primitive reflexes, adding to the pattern.4Hearing, Balance and Communication. Balance functions and primitive reflexes in dyslexic children Partial hearing adds another dimension. Research on children with hearing difficulties found significant levels of ATNR persistence alongside reading and spelling problems, suggesting that sensory processing challenges and reflex retention may compound each other.5Developmental Neuropsychology. Primary reflex persistence in children with partial hearing
The connection to attention is also worth noting. Research on children with ADHD has uncovered something interesting about sex differences: persistent ATNR appears to be more strongly linked to ADHD symptoms and balance deficits specifically in girls, while the symmetric tonic neck reflex (STNR, a related but distinct reflex) is more strongly associated with ADHD symptoms in boys.6PubMed Central. Disinhibition of Primitive Reflexes in Attention Deficit and Hyperactivity Disorder: Insight Into Specific Mechanisms in Girls and Boys This kind of finding hints that retained primitive reflexes may affect boys and girls through somewhat different pathways, which matters for both assessment and intervention. A blanket screening that checks only one reflex might miss what is going on in one sex while catching it in the other.
Why the Reflex Sometimes Persists
The honest answer is that researchers do not have a definitive causal model for why some children retain primitive reflexes while others integrate them on time. The literature points to several associations rather than proven causes. Prenatal exposure to tobacco and marijuana, use of certain medications during labor such as oxytocin, and childhood physical or emotional trauma have all been linked to higher rates of persistent primitive reflexes.7The Journal for Nurse Practitioners. Persistent Primitive Reflex and Developmental Delay in the School-Aged Child – Section: Potential Causal Relationships Other associated factors include decreased tummy time during infancy, a very short or absent crawling phase, early walking, chronic ear infections, and head injuries.
The tummy time and crawling connections make intuitive sense. Tummy time gives an infant the chance to practice lifting and turning the head while bearing weight through the arms, which is exactly the kind of active, voluntary movement that helps the cortex override primitive reflexes. Crawling on hands and knees involves rhythmic, cross-body coordination that naturally challenges and helps suppress the ATNR pattern. A baby who spends very little time in these positions may simply get fewer opportunities for the brain to practice the override. That said, plenty of children who crawled late or briefly show no signs of retained reflexes, so skipping a milestone is a risk factor, not a sentence.
How the Reflex Is Tested
Occupational therapists, developmental optometrists, and some pediatric physical therapists are the clinicians most likely to test for retained ATNR. There is no single standardized protocol that everyone uses, but the core principle is the same: put the person in a position where head turning should trigger the reflex if it is still active, and observe what happens.
The two most common testing positions are standing and on all fours. In the standing version, the person stands with arms extended in front at shoulder height, eyes closed, while the examiner slowly turns the person’s head to one side. If the ATNR is retained, the arm on the face side will drift outward or extend slightly, and the arm on the skull side will bend. In the quadruped (hands-and-knees) version, the person holds themselves still in a crawling position while the head is turned. The examiner watches for the elbows to bend or extend involuntarily. The degree of response is typically scored on a simple scale, with higher scores indicating more reflex activity.
One study of Indigenous Australian children used this type of standardized ATNR assessment and found that 65% of the sample had moderate to high levels of retained ATNR, which previous research had linked to delays in both movement skills and areas related to academic readiness.8Australasian Journal of Early Childhood. Retained primary reflexes in preprimary-aged Indigenous children: The effect on movement ability and school readiness A finding like that raises an important methodological point: the prevalence of retained reflexes in a study depends heavily on the population being tested and the sensitivity of the assessment tool. High numbers in one sample do not mean the same rate would be found in the general population. But they do suggest that screening for retained reflexes could be useful in populations already showing developmental or academic challenges.
It is worth noting that there is no universally agreed-upon clinical cutoff that defines “retained.” A low-level residual ATNR that shows up during testing but does not affect daily functioning is different from a pronounced reflex that clearly interferes with writing or balance. Context matters more than a number on a scale.
Integration Exercises and What the Research Shows
The idea behind ATNR integration therapy is straightforward: if the brain did not suppress the reflex on its own developmental schedule, you can help it along by repeating movements that challenge the reflex pattern in a controlled way. These exercises typically involve slowly turning the head while maintaining a stable body position, then gradually adding limb movements that contradict the reflex’s automatic pattern. Over weeks or months of daily practice, the theory goes, the cortex learns to override the brainstem-driven reflex.
A 12-week exercise intervention study involving children with autism spectrum disorder and ADHD found that ATNR retention levels dropped significantly in the ASD group after the program. The ADHD group showed trends toward improvement in ATNR retention as well, and their overall ADHD symptom scores on a standardized rating scale decreased significantly.9PubMed Central. Effects of a 12-Week Exercise Intervention on Primitive Reflex Retention and Social Development in Children with ASD and ADHD These results are encouraging, but the study was small, and it is hard to separate the effects of the reflex-specific exercises from the general benefits of a structured exercise program. Any 12-week program that gets children moving regularly and following instructions tends to improve attention and behavior scores.
Another study compared two different therapeutic approaches for integrating retained primitive reflexes in children with cerebral palsy: the Masgutova Neurosensorimotor Reflex Integration (MNRI) method and a sensory integration program. Both approaches led to statistically meaningful improvements in primitive reflex control and gross motor function. There was no significant difference between the two methods.10PubMed. Sensory integration versus Masgutova neuro-sensorimotor reflex integration program on controlling primitive reflexes and gross motor abilities in children with diplegic cerebral palsy That finding is interesting because MNRI is a proprietary program with specific reflex-targeted protocols, while sensory integration is a broader therapeutic framework. The fact that both worked equally well raises the possibility that what matters most is structured, repeated movement practice rather than the specific brand of therapy.
Research specifically examining whether ATNR integration exercises can improve attention in young children has also been conducted, though some of this work comes from doctoral dissertations rather than peer-reviewed trials, which means the findings deserve a bit more caution.11Digital Commons at Liberty University. Improving Inattentiveness Through Asymmetric Tonic Neck Reflex Integration Exercises: A Quantitative, Quasi-Experimental Study The broader picture is that the evidence base for reflex integration therapy is growing but still relatively thin compared to, say, the evidence behind speech therapy for language delays or occupational therapy for sensory processing. This does not mean it is ineffective. It means the research has not yet caught up to the clinical practice, which is common in pediatric therapy fields.
Common Misconceptions About Retained Reflexes
One of the most persistent misunderstandings is that a retained ATNR causes conditions like dyslexia, ADHD, or autism. The research consistently shows an association between retained primitive reflexes and these conditions, but the relationship is correlational, not causal.3PubMed. Prevalence of persistent primary reflexes and motor problems in children with reading difficulties A child with ADHD may have a retained ATNR because both reflect underlying differences in how their nervous system developed, not because one caused the other. Programs that market reflex integration as a cure for learning disabilities are overstepping the evidence.
Another misconception is that retained reflexes are rare or only found in children with diagnosed neurological conditions. Low levels of reflex persistence are actually fairly common in otherwise healthy preschool-aged children and often resolve without intervention as the child gets more active and their nervous system continues to mature. The clinical concern arises when the retention is pronounced and clearly interfering with function.
A third misunderstanding involves the idea that if you did not catch and address a retained reflex in early childhood, the window has closed. Adults can and do work on reflex integration, although the evidence base for adult intervention is much thinner. The brain retains plasticity throughout life, and the same principle of repeated movement practice applies. Some adults who seek out reflex integration report improvements in coordination, handwriting, and even driving comfort, though controlled studies in adults are scarce.
Container Culture and Modern Infant Equipment
One factor that has drawn increasing attention from pediatric therapists is the amount of time modern infants spend in positioning devices. Car seats, bouncers, rockers, and infant carriers keep babies in a reclined or semi-reclined position where they are not practicing the active, weight-bearing movements that help integrate primitive reflexes. When these devices become the default positioning throughout the day rather than just for transportation, the result has been described as “container baby syndrome.”12Pediatria Polska. Container baby syndrome – has infant equipment overuse an impact on motor skill development?
Spending prolonged time in a forced reclined position limits the spontaneous motor activity that drives neurological maturation. Babies who rarely experience tummy time, who are propped into sitting before they can achieve it independently, or who are placed in standing devices before their trunk muscles are ready may miss critical movement experiences. This does not mean that using a bouncer for 20 minutes while you eat breakfast will harm your child. The concern is about chronic overuse replacing floor time and active exploration as the infant’s primary daily experience.
The connection to retained ATNR is logical. Tummy time and crawling are two of the most important natural movement patterns for challenging and overriding the ATNR pattern. A baby on their belly who lifts their head and pushes up through their arms is practicing exactly the kind of voluntary motor control that helps the cortex suppress the automatic fencing response. Reducing opportunities for that practice may slow the integration process. Pediatric therapists generally recommend generous amounts of supervised floor time starting from the early weeks of life, with tummy time being especially valuable even when the baby initially protests it.
When Primitive Reflexes Re-Emerge in Adults
Primitive reflexes are not exclusively a pediatric concern. In adults, the reappearance of reflexes like the ATNR can signal neurological damage or degeneration. The tonic neck reflex was first described in the context of neurological disease by Josef Gerstmann in the early twentieth century, well before its role in normal infant development was mapped out by Arnold Gesell.13Neurology. The tripartite origins of the tonic neck reflex: Gesell, Gerstmann, and Magnus Gerstmann described the reflex in what would later be recognized as an early case of a rare prion disease, highlighting that when higher brain centers are damaged, the primitive patterns they had been suppressing can resurface.
In modern clinical practice, the reappearance of the ATNR and other primitive reflexes in adults is associated with conditions like stroke, dementia, traumatic brain injury, and advanced Parkinson’s disease. The mechanism is essentially the reverse of infant development: instead of the cortex gradually gaining control over brainstem reflexes, cortical damage or degeneration releases those reflexes from suppression. Neurologists sometimes test for these “frontal release signs” as part of a neurological examination, and their presence can help localize the site of damage or confirm the severity of cognitive decline. The adult re-emergence of the ATNR is a fundamentally different clinical situation from a child who never fully integrated the reflex, but the underlying neurology connects the two: both reflect the balance of power between lower and higher brain centers.