The age of disappearance is 3 weeks but then becomes voluntary head turning (Berk, p. 101).
Sucking is a self-explanatory reflex that allows the baby to feed. I have noticed that the baby does suck at different rates and patterns once in a while. If he is tired the sucking seems to relax him until he falls asleep. He sucks slower and slower until he stops. In the text it is mentioned that this reflex and others can control stress and allow caregivers to comfort the baby (Berk, p. 101). Sometimes the baby will stop sucking if he hears a certain noise or sound but he will continue to suck shortly after that. This occurs because new or unfamiliar sound are interesting to the infants and the infant will stop doing what it was before hearing the sound until the sound becomes familiar and boring (lecture, 9/29/03).
The swimming reflex I did not try on the baby. This reflex is stimulated when you put an infant face down towards water and the infant will paddle and kick in a swimming motion. This will help the infant to survive if it is dropped into water (Berk, p. 101). The swimming reflex lasts around 4 to 6 months. In one other class I took a couple years ago we talked about this swimming reflex and how it was related to our environment in the uterus. We were all once submerged in fluid until birth and that experience in the womb plays a part in an infant's response to being placed in water. I also heard that we are all capable of breathing underwater shortly after birth. Maybe a new infant would try to breathe water if it was submerged under water.
The Moro reflex can be stimulated in two different ways. A loss of support or a loud noise causes the infant to make the back arch, legs extend, throw arms outward, and then bring the arms in toward the body (lecture, 9/24/03). The purpose of this reflex is that it may have helped the infant cling to the mother (Berk, p. 101). When I tried to elicit this response the baby did not try to arch his back or wave his arms and legs.