Which reflex involves stroking the sole of the foot and seeing the toes fan out?

The reflex that involves stroking the sole of the foot and observing the toes fan out is the Babinski reflex. This reflex is significant in assessing the neurological function in infants. When the sole of the foot is stroked from the heel to the toes, the normal response in infants is the extension and fanning of the toes, particularly the big toe, which can be indicative of proper neurological development.

In adults, however, this reflex should be absent; instead, a flexor response occurs where the toes curl downwards, indicating that the neural pathways are intact, and the fetal reflex has faded due to maturation of the central nervous system. The presence of the Babinski reflex beyond infancy, or its absence in newborns, can indicate underlying neurological issues.

The other reflexes mentioned do not involve the fan out response of the toes. The Moro reflex is an infant's startle response, the startle reflex is a response to sudden loud sounds or movements, and the rooting reflex is associated with feeding, where an infant turns its head towards a stimulus on its cheek. Each of these reflexes has different characteristics and implications for development, making the identification of the Babinski reflex particularly important in clinical assessments of infants.