Final answer:
The Moro reflex is a primitive response that becomes active at birth and is typically observed up until three to four months of age. It involves spreading the arms, bringing them back in, and usually crying, to potentially prevent a fall.
Step-by-step explanation:
The Moro reflex is an involuntary motor response observed in infants, which becomes active starting at birth. This reflex is part of the infant's primitive reflexes that aid in survival.
The Moro reflex is characterized by three distinct components: first, the infant suddenly spreads out the arms; second, the arms are brought back in toward the body; and lastly, the reflex usually triggers crying.
This reflex is critical as it potentially allows the infant to reach out and grab onto the mother or caregiver to prevent a fall. The Moro reflex typically disappears at around three to four months of age.