Perceptual learning is an example of plasticity in the brain. This thesis investigates perceptual learning with feedbacks in psychophysical experiments and different theoretical models. The first psychophysical experiment tests the discrimination performance with and without feedbacks, while the second experiment tests the influence of feedbacks on an irrelevant task. In both psychophysical experiments the discrimination threshold decreased consistently for all subjects and tested orientations. As expected, the discrimination performance increased most for the feedback correlated orientation....