Toward the end of the first year, babies become more skilled at using their thumbs and forefingers to investigate objects. The ability to use a pincer grasp to pick up small objects and turn and twist items enables children to handle dials, knobs, and small moving objects like balls or bugs.
Halverson, H. M. (1931). An experimental study of prehension in infants by means of systematic cinema records. Genetic Psychology Monographs, 10, 107