What type of reflex causes the toes to hyperextend when the outer sole of the foot is stroked in an infant?

The Babinski reflex is the correct answer because it specifically refers to the involuntary response observed in infants when the outer sole of the foot is stroked. In this response, the toes fan out and hyperextend, which is considered a normal physiological reaction in infants up to about 12 months of age. The presence of the Babinski reflex is often used as an important indicator of neurological health during early development.

In contrast, the rooting reflex is a different response where an infant turns its head towards a stroking sensation on the cheek, which is linked to feeding. The Moro reflex involves a startle response when a baby feels as though it is falling, causing the arms to extend and then quickly retract. Lastly, the grasp reflex refers to an infant's instinctual grip when an object touches the palm of their hand. Each of these reflexes serves different developmental purposes and indicates varying aspects of neurological function, but the hyperextension of the toes specifically points to the Babinski reflex.