Then he tries again, proceeding now on the knowledge which the first effort gave him; and his trial is less uncouth because he now suppresses some of the hindering grimacing movements and retains the ones which he sees to be most nearly correct.

Again he tries, and again, persistently but gradually reducing the blundering movements to the pattern of the copy, and so learning to perform the act of skill.
The massive and diffused movements which he makes by wriggling and fussing are also of direct use to him.

They increase remarkably the chances that among them all there will be some movements which will hit the mark, and so contribute to his stock of correct Equivalents.
Dogs and monkeys learn to unlock doors, let down fence rails, and perform relatively complex actions by experimenting; persistently with many varied movements until the successful ones are finally struck.
This is the type of all those acts of experimenting by which new complex movements are acquired.

In children it proceeds largely without interference from others; the child persists of himself.

He has greater ability than the animals to see the meaning of the completed act and to really desire to acquire it.