A child’s ability to use language corresponds closely to his ability to deal with concepts and relationships. This correspondence is illustrated by an experiment in which pre-school children were taught to select the smallest of a pair of squares, each mounted on the lid of a box. If the child chose the smaller square, he found the box open and an attractive toy inside. If he mistakenly chose the larger square, he found the box locked.
The child began by learning to choose a six-inch square in preference to an eight-inch one. When he had learned to choose the six-inch square regularly, he was ready for the crucial tests with smaller squares. In this experiment, although all children did well on the near pair, they showed a striking increase in success with age on the remote pair.