Learning is never sealed off in compartments. What a child has already mastered is carried over and used when a new task is met, and psychologists give this carrying over a definite name. The effect may be helpful, as when knowing addition eases multiplication, or harmful, as when a habit formed in one script interferes with another.

The carrying over of the effect of earlier learning to later learning is explained by Thorndike through the identical elements shared by the two tasks, and by Judd through the generalisation of principles. The whole idea of arranging subjects in a graded order and of teaching general rules rests on it, since each class is expected to help the next.

The other choices name different things. Keeping a learnt response alive by repetition concerns retention within one task. Copying a model is one way of acquiring a response, not of carrying it forward. Forming a link between a stimulus and a response describes how a single habit is built.

Transfer training option is correct.