AGE, SEX, AND IQ DIFFERENCES IN THE CHARACTERISTICS OF THE CONCEPTUAL PERFORMANCE OF ELEMENTARY SCHOOL CHILDREN WERE STUDIED. PERFORMANCE MEASURES WERE OBTAINED THROUGH THE USE OF DUNN'S OBJECT SORTING TASK (OST) WHICH PROVIDED SUCH INDICATORS AS SIZE OF THE COGNITIVE MATRIX, ACCESSIBILITY OF THE CONCEPTS IN THE MATRIX, AND DEGREE OF PRECISION IN THE VERBAL REPRESENTATION OF THE CONCEPTS IN THE MATRIX. THE SAMPLE CONSISTED OF 99 UPPER MIDDLE CLASS ELEMENTARY SCHOOL CHILDREN WITH A MEAN STANFORD BINET IQ OF 126. THE RELATIVE CONTRIBUTIONS OF AGE, SEX, AND IQ TO OST PERFORMANCE PATTERNS WERE ASSESSED BY ANALYSIS OF VARIANCE AND A FILTER MEANS PROGRAM. THE RESULTS OBTAINED WERE SUGGESTIVE OF DIFFERENTIAL EFFECTS OF AGE AND IQ LEVELS ON COGNITIVE PERFORMANCE. FOR GIRLS, LEVEL OF IQ WAS NOT ASSOCIATED WITH CONCEPT FORMATION AND UTILIZATION ON THE TASK, WHEREAS AGE WAS. THE OPPOSITE WAS TRUE FOR BOYS. THE COMPLEX PATTERNS OF INTERACTION BETWEEN AGE, SEX, AND IQ SUGGEST THE NEED FOR FURTHER RESEARCH. THIS DOCUMENT APPEARED AS STUDY 4 IN SCHOOL ANXIETY AND COGNITIVE FUNCTIONING/ EXPLORATORY STUDIES, REPORT 4, IRCOPPS MIDWEST RESEARCH CENTER FOR PUPIL PERSONNEL SERVICES, ANN ARBOR, MICHIGAN, PP. 131-140. (PS)