The extrusion reflex, also known as the tongue-thrust reflex, is one of several primitive, involuntary movements present in newborns. This automatic response causes a baby’s tongue to move forward, often protruding past the lips. It is a fundamental neurological function that infants do not consciously control, serving a specific purpose early in life. Like other primitive reflexes, it is a temporary biological feature that appears at birth and disappears as the baby matures.
What the Extrusion Reflex Looks Like
The physical action of the extrusion reflex is easily observable and can be mistaken by parents for the baby rejecting food. When a non-liquid substance or object, such as a spoon or solid food, touches the infant’s lips or the front of the tongue, the motor response is triggered. This stimulation causes the tongue muscles to contract, thrusting the tongue out of the mouth.
This forward tongue movement is distinct and noticeable when parents attempt to introduce a spoon. Even if the baby seems interested, the tongue automatically pushes the spoon and its contents away from the oral cavity. The reflex effectively prevents anything solid or semi-solid from moving toward the throat to be swallowed. It is a physical rejection of anything that is not a nipple or liquid.
The reflex can be observed by gently touching the baby’s lower lip or tongue with a clean finger or the tip of a small spoon. If the reflex is active, the baby’s tongue will immediately press forward and out. This action signals that the involuntary neurological pathway is still dominant, meaning the baby’s oral motor skills are not yet mature enough to handle textured foods.
Why Infants Have This Reflex
The physiological function of the extrusion reflex is two-fold, supporting both nutrition and safety in early life. Primarily, the reflex works with the sucking reflex to ensure successful liquid feeding from a breast or bottle. The forward thrusting motion helps the baby maintain the correct oral posture for latching and suckling, facilitating the intake of breast milk or formula.
The reflex also serves as a protective mechanism against aspiration and choking. Since a newborn’s swallowing abilities are only developed enough to manage liquids, the reflex acts as a natural barrier. Any foreign object or substance that enters the mouth will be forcefully ejected by the tongue, preventing it from accidentally entering the airway or being ingested.
This biological safeguard ensures that for the first several months, the baby is protected from swallowing anything their immature systems are not prepared to handle. The reflex effectively limits the baby’s diet to only liquids, which are safe for their developing swallowing mechanisms.
The Timing of Reflex Disappearance
The extrusion reflex is a temporary developmental stage, and its disappearance signals an infant’s increasing maturity. In most infants, this reflex begins to diminish between four and six months after birth. The loss of this reflex is considered a significant developmental milestone, as it signals a change in the baby’s oral motor control.
Once the reflex integrates, the baby gains the ability to voluntarily control tongue movements, a necessary skill for eating solid foods. The tongue’s movement shifts from an automatic forward thrust to a more coordinated action that moves food to the back of the mouth. This backward and side-to-side manipulation is the precursor to chewing and swallowing solids.
The absence of the extrusion reflex is considered a primary indicator that an infant is developmentally ready to begin complementary foods. If a parent offers pureed food and the baby pushes it out repeatedly, the reflex is likely still active, and they should wait a week or two before trying again. Waiting until the reflex is gone simplifies the feeding process, as the baby is then physically capable of accepting and swallowing new textures.
If a strong tongue-thrusting action persists past seven months, it is advisable to discuss it with a pediatrician. In rare cases, a persistent tongue thrust may continue into childhood, which can be associated with later difficulties in speech development or dental alignment. For the vast majority of infants, however, the extrusion reflex simply fades away as their oral control matures, paving the way for the exploration of solid foods.