When an object like a ball is moved some distance away, the eye perceives the ball as getting smaller, even though the ball remains the same actual size. Adults know this and recognize that an object is the same despite its smaller appearance. This concept is called “size constancy,” and infants understand this concept at birth. “Shape constancy” enables young children to recognize that an object is the same even if distance appears to change the object’s shape. Experiments show that infants can recognize that an object is the same even when it appears smaller or otherwise different to them from a distance.
Bower, T. (1989). The Rational Infant. New York: Freeman.