The Moro Reflex is a reponse found in all healthy infants at birth. The infant throws out his arms, clenches his
fists, and
arches his
back in an
embracing gesture when either his head suddenly decreases in elevation or when he hears a loud noise. This disappears at about six months.
It is thought that in some distant evolutionary past, when before car seats and strollers, this reflex would have helped the infant cling to its mother while being carried around. In the first week, the baby's grip is so strong that it can support its own weight.