BOTH COGNITIVELY-ORIENTED AND RESPONSE-ORIENTED THEORIES OF PERCEPTUAL LEARNING ARE DISCUSSED AND CONTRASTED WITH A STIMULUS-ORIENTED THEORY. PERCEPTUAL LEARNING IS DEFINED AS AN INCREASE IN SPECIFICITY OF DISCRIMINATION OF THE STIMULUS INPUT. THE AUTHOR DESCRIBED WHAT IS LEARNED IN PERCEPUTAL LEARNING AS () THE DISTINCTIVE FEATURES OF THINGS, (2) INVARIANTS OF EVENTS OVER TIME, AND (3) HIGHER ORDER STRUCTURES OF BOTH THINGS AND EVENTS. WHAT IS LEARNED WAS SAID TO BE SELECTED BECAUSE IT PROVIDES A "REDUCTION OF UNCERTAINTY." FOUR PRINCIPLES THAT ARE IMPORTANT IN THE APPLICATION OF THE AUTHOR'S VIEW OF PERCEPTUAL LEARNING TO EDUCATION WERE STATED--(1) TASKS CAN BE ANALYZED INTO UNITS OF PERCEPTUAL CONTENT WHICH FORM HIERARCHIES, (2) LOWER ORDER UNITS ARE DISTINGUISHED BY DISTINCTIVE FEATURES, (3) HIGHER ORDER UNITS ARE DISTINGUISHED BY STRUCTURE, (4) THE STRATEGY OF EXPLORATION AND PERCEPTUAL SEARCH DEVELOPS WITH AGE AND EDUCATION. THIS PAPER WAS PREPARED FOR THE SYMPOSIUM ON RESEARCH APPROACHES TO THE LEARNING OF SCHOOL SUBJECTS (UNIVERSITY OF CALIFORNIA AT BERKELEY, OCTOBER 28-29, 1966). (AL)