c7f1ccc7___open_books_for_an_open_world__Response
[Reflex] Tonic neck [Stimulation] Turn the baby's head to one side while the baby is awake. [Age of disappearance] 4 months [Function] This may prepare for voluntary reaching. [Response] 
This will cause the baby to extend one arm in front of its eye or to the side to which the head has been turned.
Human Physiology/Print Version - Wikibooks, open books for an open world