The Symmetrical Tonic Neck Reflex (STNR) is a primitive reflex in infants that aids early motor development.[1]
## Development Timeline
STNR typically emerges between 6-9 weeks of age, becomes prominent during crawling practice around 6-9 months, and integrates (fades) by 9-11 months, though it's significantly diminished by 2-3 years.
## How It Works
When an infant on hands-and-knees extends their neck (looks up), the arms straighten while legs bend; flexing the neck (looks down) bends the arms and straightens the legs. This rocking motion builds shoulder and hip stability for crawling.
## Role in Growth
It supports posture, balance, eye coordination (near-far focus), and upper-lower body separation, bridging reflexes like TLR for transitions to walking.
## Retained STNR Effects
If unintegrated beyond toddlerhood, it may cause poor posture, W-sitting, vision strain, handwriting-reading issues, fatigue, balance problems, or ADHD-like symptoms.
