Problems of decision criterion in the tasks of image analysis and pattern recognition are considered. Overlearning as a practical consequence of fundamental paradoxes in inductive inference is illustrated with examples. Theoretical (on the base of algorithmic complexity) and practical formulations of the minimum description length (MDL) principle are given. Decrease of the overlearning effect is shown in the examples of modern recognition, grouping, and segmentation methods modified with the MDL principle. Novel possibilities of construction of learnable image analysis algorithms by representation optimization on the base of the MDL principle are described