 To be authentic cases of learning, perceptual changes have to be the result of a learning process. As a contrast case, suppose someone undergoes a long-term change in their perception due to a brain lesion. Such a change in perception does not result from a learning process, since the change in perception comes from the lesion, rather from practice or experience. Because of this, the case does not count as an instance of perceptual learning, even though it involves a long-term change in perception.