Answer:
Fringe.
Step-by-step explanation:
Both the central and fringe vision are included in the whole field of vision where the central vision would be what is directly ahead of you and a few degrees out of that, meanwhile the fringe vision is part of the peripheral vision that helps monitor everything that is defined by the central vision. Taken this into account, is safe to say that, in the example given, the motion of the fringe vision would be the most helpful and important to notice a child running in an individual's periphery.