Final answer:
The Moro or startle reflex is a primitive reflex found in newborn infants, involving spreading the arms, bringing them back in, and usually crying. This reflex aids in survival by helping the infant maintain physical contact with a caregiver. It is typically present at birth and fades by three to four months of age.
Step-by-step explanation:
The Moro Reflex in Infants
The Moro reflex, also known as the startle reflex, is a primitive reflex found in newborn infants. This reflex is characterized by a rapid motor response to a sensation of falling, which includes three distinct components: the arms suddenly spread out, then are brought back in toward the body, and generally, this is followed by crying. It is typically present from birth and lasts until about three or four months of age.
Newborns exhibit several such instinctive behaviors or reflexes, which are crucial for their survival. These include not only the Moro reflex but also the grasping reflex, where a baby will instinctively grasp a finger placed in its palm. The presence of these reflexes is part of the innate behaviors that allow a newborn to maintain close physical contact with their caregiver—a critical aspect in the initial months of life.
Such reflexes are observed to aid infants in securing themselves to their mother or a caregiver, which in turn decreases the likelihood of falling and promotes the satisfaction of their basic need for constant physical contact. It is these reflexes that would have been vital for the survival of infants in prehistoric times, although they naturally diminish as the child grows.