DUNN'S PHYSICAL ANALOG THEORY OF COGNITIVE STRUCTURE AND FUNCTION WAS EXTENDED TO THE ANALYSIS OF CONCEPTUAL FUNCTIONING ASSOCIATED WITH EMOTIONAL DISTURBANCE AND MENTAL RETARDATION IN CHILDREN. THE THEORY, WHICH DESCRIBES THE INTERNAL REPRESENTATION OF INFORMATION IN THE FORM OF A COGNITIVE MATRIX OF ASSOCIATED DIMENSIONAL CONCEPTS, HAS BEEN OPERATIONALIZED BY DUNN IN THE FORM OF AN OBJECT SORTING TASK (OST). THE OST WAS INDIVIDUALLY ADMINISTERED TO SAMPLES OF 40 MALE PUPILS ENROLLED IN PUBLIC SCHOOL CLASSES FOR THE EMOTIONALLY HANDICAPPED, THE MENTALLY HANDICAPPED, AND NORMAL FOURTH-, FIFTH-, AND SIXTH-GRADERS. THE THREE GROUPS WERE EQUATED FOR AGE, AND THE EMOTIONALLY DISTURBED AND NORMAL GROUPS WERE ALSO EQUATED FOR IQ. ON ALL QUANTITATIVE DIMENSIONS OF TASK PERFORMANCE, RETARDATES WERE INFERIOR TO NORMALS, AS PREDICTED BY THEORY. HOWEVER, RETARDATES ALSO DIFFERED IN MANY QUALITATIVE RESPECTS, OFTEN TO A GREATER DEGREEE THAN DID DISTURBED SUBJECTS WHO GENERALLY OCCUPIED A POSITION INTERMEDIATE BETWEEN THE OTHER GROUPS IN TERMS OF QUANTITATIVE INDEXES. THE SPECIAL GROUPS WERE HIGHLY VARIABLE, HOWEVER, ON MOST SCORING DIMENSIONS. A CLUSTER ANALYSIS YIELDED FIVE MIXED-MEMBERSHIP GROUPS WITH HIGH "SIMILARITY COEFFICIENTS." THIS APPROACH OFFERED A POTENTIAL MEANS OF DESIGNATING MEANINGFUL CLASSIFICATIONS ALONG COGNITIVE DIMENSIONS. (PS)