Perceptual learning is learning to perceive and is essential for all forms of perception and learning. For a long time it was believed that perceptual learning was a simple process suitable as a model for studying general mechanism of learning. Researchers set out on a quest to conquer this "holy grail" of learning. It proved an effortful journey. Decades later, the grail remains elusive and the field of perceptual learning has established itself a research field of its own. In this work, I show that simple tasks do not follow previously established rules of perceptual learning. Instead it seems that perceptual learning rules, which were once believed to generalize over paradigms, depend on the experimental paradigms themselves. Hence, systematic studies are required to comb out the rules of perceptual learning and generization should be done with caution. In conclusion, there is no holy grail of perceptual learning.