Babies exhibit a variety of fascinating—and sometimes puzzling—behaviors. That adorable grin? It might just be gas. And when your little one wraps their tiny fingers around yours, it feels like a profound connection, but it’s likely a reflex. So, if you catch your baby lying on their back, seemingly preparing for a duel like a miniature fencer, don’t assume they’re destined for athletic greatness just yet. What you’re witnessing is the tonic neck reflex, which has two forms: asymmetrical and symmetrical. Here’s what you should know about both.
What is Asymmetrical Tonic Neck Reflex (ATNR)?
Most discussions about the tonic neck reflex focus on the asymmetrical tonic neck reflex (ATNR), often referred to as the “fencing position.” In this reflex, when a baby turns their head to one side, the arm on that side extends while the opposite arm bends at the elbow. This reflex typically lasts until your baby is about five to seven months old. So, if your little one displays ATNR around Halloween, you might be halfway to crafting a charming Robin Hood costume.
Why Does the Tonic Neck Reflex Occur?
One explanation for this reflex is that it aids in smoother passage through the birth canal during delivery. Once in the world, ATNR helps babies discover their hands and develop hand-eye coordination. If you’d like to see this reflex in action, gently lay your baby on their back and turn their head to one side. If ATNR is present, the arm corresponding to the turned head will extend, while the other arm will appear to flex next to their head.
What is Symmetrical Tonic Neck Reflex (STNR)?
Unlike ATNR, which develops in utero, the symmetrical tonic neck reflex (STNR) typically emerges between six and nine months of age. This reflex is crucial as it helps babies progress to being on their hands and knees — hence the nickname “crawling reflex.” The STNR occurs when a baby moves their chin toward their chest, causing their legs to straighten and arms to bend, or when they lean back, prompting their legs to bend and arms to straighten.
Watching STNR can be delightful, but it’s also an important developmental stage, teaching babies to coordinate their upper and lower bodies. However, it usually fades between nine and twelve months as they learn to walk. If your child continues to display STNR past their first birthday, don’t worry; developmental milestones vary widely. You may notice them doing things like crawling on all fours, scooting while seated, or transitioning directly to walking without a crawling phase.
If you have concerns about your baby’s development, it’s always best to consult with your pediatrician. They can provide guidance and reassurance.
Other Reflexes in Newborns
There are several other reflexes that explain your baby’s movements:
- Moro Reflex: When startled, a baby will cry, throw back their head, and pull in their limbs.
- Rooting Reflex: This reflex occurs when the corner of a baby’s mouth is touched, leading them to search for the nipple.
- Grasp Reflex: Triggered by a light touch to the palm, causing the baby to grasp.
- Suck Reflex: This prepares the baby for nursing, beginning around the 32nd week of pregnancy.
- Stepping Reflex: Sometimes called the walking or dancing reflex, a baby appears to take steps when held upright with their feet touching a surface.
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Summary
The tonic neck reflex, which includes both the asymmetrical and symmetrical forms, is a fascinating aspect of a baby’s early development. Understanding these reflexes can help parents make sense of their baby’s movements, ensuring they know what to expect as their little ones grow.
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