The head-righting reflexes are caused by the labyrinth, a complex structure deep within the ear that contains membranes and cavities filled with fluid. Movement of the head stimulates the labyrinths, resulting in the reflexes.
The labyrinthine-head righting reflex occurs around two to three months of age and is linked to the vestibular motor system. It enables the infant to start lifting their head while on the tummy, and its influence is seen in the progress an infant makes as they start raising their head in the prone position.