Final answer:
A newborn should exhibit a positive Babinski sign, where their foot dorsiflexes and toes splay upon stimulation of the foot's plantar surface. It indicates healthy lower motor neurons and neuromuscular function. This reflex changes to negative as maturation occurs and is typical in walking individuals.
Step-by-step explanation:
A newborn should have a positive Babinski sign. This is observed when a stimulus, such as a fingertip, is brushed along the plantar surface of the infant's foot, causing the foot to dorsiflex and the toes to extend and splay out. This response is part of the newborn's reflexes and indicates that the lower motor neurons (LMN) and neuromuscular function are intact.
As the child grows and the nervous system matures, the reflex changes and a negative Babinski sign becomes the normal response. For adults, a positive sign can indicate neurological problems due to issues such as reduced myelination of the spinal tract.