The STNR also plays a role in the infant’s development of visual accommodation. This is the ability to accommodate their visual field from near to far away and vice versa with ease. Many children with a retained STNR will have visual processing delays.
The Symmetric Tonic Neck Reflex (STNR) is a primitive reflex that is present before the age of 12 months. The STNR is appears between 6 and 9 months of life and has a lifespan of 2-3 months. When a reflex disappears, we say it integrates. Integration happens as child move from sitting to four point kneeling and back. When a child is crawling, the STNR is fully integrated.
When the STNR is present, we observe a direct correlation of activity between the upper body and lower body. What happens at the neck affects the lower body. As the infant moves from prone (on belly) to quad (on hands and knees), they will begin to extend their neck – look up, and flex their neck – look down. These movements will then elicit a response in the upper and lower limbs. During neck extension (when the infant looks up), the arms will straighten while the legs will flex/bend. During neck flexion (looking downward), the opposite will occur – the arms will flex/bend while the legs will straighten – moving the infant into a somewhat down dog position.
As they learn to crawl, the STNR will start to integrate. The “rocking” movement that infants do while on hands and knees, right before they begin to crawl is often the integration process of the STNR. The STNR should be fully integrated by 12 months.