The Babinski reflex is a natural response seen in infants when the sole of their foot is stroked. In this reflex, the big toe bends upward while the other toes fan out. This reaction is a sign of healthy neurological development in babies, typically observed in children up to about two years old. As children grow, the Babinski reflex usually disappears, and the toes begin to curl downward instead. If the reflex persists in older children or adults, it may indicate potential issues with the nervous system or brain, prompting further medical evaluation.