STNR stands for Symmetrical Tonic Neck Reflex, sometimes called the crawling reflex. It’s an automatic movement pattern that appears in babies and helps them coordinate their arms and legs as they learn to crawl. When a baby looks up, their arms straighten and their legs bend. When they look down, the opposite happens: their arms bend and their legs straighten. This reflex is meant to serve its purpose during infancy and then fade away, but when it doesn’t, it can cause noticeable problems in older children.
How the STNR Works
The STNR links head position to limb movement. It’s an involuntary response, meaning the baby doesn’t choose to do it. The reflex essentially divides the body into upper and lower halves: when one half flexes, the other extends. This automatic pattern gives babies a way to push up from lying flat onto their hands and knees, which is the starting position for crawling.
Think of it as training wheels for coordinated movement. Before a baby can independently control all four limbs, the STNR provides a built-in system that pairs arm and leg movements together based on where the head is pointing. Once a baby has practiced crawling enough and the brain develops more mature motor control, the reflex is no longer needed and typically integrates, meaning the brain overrides it so head movement no longer automatically triggers limb responses.
What Happens When STNR Doesn’t Fade
When the STNR persists past the crawling stage, it’s called a “retained” reflex. This means the automatic link between head position and limb movement is still active, even though the child has long since learned to crawl. The effects can show up in everyday activities that adults might not immediately connect to a reflex issue.
One of the most recognizable signs is W-sitting, where a child sits on the floor with their knees bent and feet splayed out to either side, forming a W shape. Children with a retained STNR often prefer this position because it lets them keep their legs bent while their arms are free and extended, which feels more comfortable when the reflex is still influencing their body. Poor posture at a desk is another common sign. Because looking down (to read or write) triggers the arms to bend and legs to straighten, a child may slump forward, have trouble staying upright in a chair, or seem unable to sit still.
Effects on Vision and Reading
A retained STNR can interfere with visual skills in ways that look like a learning problem. Because the reflex ties head movement to the rest of the body, shifting focus between near and far objects becomes mechanically harder. A child copying notes from a whiteboard, for example, has to constantly refocus between the board (far) and their paper (near). With a retained STNR, each of those head movements subtly disrupts the body’s positioning and the eyes’ ability to smoothly readjust.
Specifically, a retained STNR affects hand-eye coordination, the ability to cross the body’s midline (reaching across the center of the body), and binocular vision, which is the ability of both eyes to work together to maintain clear focus. These difficulties can make reading slower and more effortful, not because of an intellectual problem but because the visual mechanics aren’t working smoothly.
Connection to ADHD and Attention
Retained primitive reflexes, including the STNR, have been studied in children with ADHD. A study published in Frontiers in Psychiatry found a statistically significant correlation between retained STNR scores and ADHD symptom severity in boys, with a moderate correlation strength. The same study found that retained STNR in boys was also significantly linked to balance problems, particularly difficulty walking forward with eyes closed.
This doesn’t mean a retained STNR causes ADHD. But it suggests that some of the restlessness and difficulty concentrating seen in children with ADHD may be partly driven by the body constantly fighting against a reflex that should have integrated years earlier. A child whose body involuntarily responds every time they tilt their head has to spend extra energy just staying in position, leaving less capacity for focus and attention. The correlation was also found between a related reflex (the ATNR, or Asymmetrical Tonic Neck Reflex) and ADHD symptoms in girls, pointing to broader patterns between retained reflexes and attention difficulties across sexes.
Signs to Look For in Older Children
Because a retained STNR affects so many everyday activities, the signs can be easy to mistake for laziness, clumsiness, or behavioral issues. Some of the more common indicators include:
- W-sitting preference, especially past age 4 or 5
- Poor desk posture, slumping or propping the head up with a hand while writing
- Difficulty copying from a board, losing their place frequently
- Trouble sitting still, constantly shifting, rocking, or wrapping legs around chair legs
- Messy handwriting that doesn’t improve with practice
- Clumsiness or poor coordination, particularly in activities that require upper and lower body to work independently
These signs tend to become more obvious once a child starts school, because the demands of sitting at a desk, reading, and writing put sustained pressure on exactly the systems the STNR disrupts. Occupational therapists and developmental specialists can assess for retained reflexes through specific movement tests and, if needed, guide exercises designed to help the brain integrate the reflex pattern that should have resolved in infancy.