AbstractIn this paper, pattern recognition is reconsidered in geometrical terms, and issues in learning theory that require further research are discussed. First, it is shown that there is learning that is easy for humans and learning that is difficult for humans, which has not been duly taken into account in existing learning theories. Then the importance of pattern structure in learning is demonstrated. For the purpose of development of a new learning theory, the structure of pattern recognition is revised, and all problems of recognition are shown to have a geometrical structure, thus being treatable by means of transformation groups. In closing, issues are put forward that should be studied in the framework of new learning theory with regard to pattern structure, and coordination between theory and experiments in pattern recognition is discussed. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 33(13): 103–110, 2002; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/scj.1177