What reflex is observed when a baby is held upright and their feet touch a flat surface?

The step reflex, also known as the walking or dance reflex, is the correct response observed when a baby is held upright and their feet make contact with a flat surface. This reflex occurs when an infant appears to take steps or walk when their feet touch the ground, demonstrating a primitive motor response that is innate and not consciously controlled.

This reflex generally appears at birth and can typically be observed in newborns for the first few months of life. It serves as an early indication of the child's neurological development and motor skills. As the infant grows and their muscular and neural functions mature, this reflex gradually diminishes, and voluntary walking takes its place.

In contrast, the startle reflex is an automatic response to a sudden noise or movement; the grasp reflex involves curling the fingers around an object placed in their hand; and the sucking reflex is a response that helps the infant feed by sucking on anything that touches the roof of their mouth. These reflexes serve distinct purposes and start developing at different stages of infancy, but they do not correlate with the stepping movement observed when the baby's feet touch a surface.