IN THE LONGITUDINAL BERKELEY GROWTH STUDY, SUBJECTS WERE TESTED AT 16, 18, 21, AND 26 YEARS ON THE WECHSLER-BELLEVUE, AND AT 36 YEARS ON THE WECHSLER ADULT INTELLIGENCE SCALE, WHICH CONTAIN BOTH VERBAL AND NON-VERBAL SUBSCALES. THE MOST CONSISTENT INCREASES IN MEAN SCORES OVER THE PERIOD WERE IN INFORMATION, VOCABULARY, AND COMPREHENSION. DIGIT SPAN AND ARITHMETIC SCORES LEVELED OFF, AND WOMEN'S SCORES ON SEVERAL TESTS DECLINED AFTER AGE 26. TEST-RETEST CORRELATIONS DURING AGES 16-26 WERE MORE CONSISTENT AMONG MEN THAN AMONG WOMEN, MOST NOTABLY IN VOCABULARY AND INFORMATION, LESS SO IN SIMILARITIES, DIGIT SPAN, AND BLOCK DESIGN. BY CONTRAST, CHILDHOOD SCORES OF MALES WERE LESS STABLE THAN THOSE OF FEMALES, SUGGESTING SEX-LINKED, DIFFERENTLY-TIMED INTELLIGENCE FACTORS INFLUENCING ADULT MENTAL PERFORMANCE. FINALLY, AT AGE 36, MEN SEEMED TO BE ACHIEVING CLOSER TO CAPACITY THAN WOMEN. IT WAS CONCLUDED THAT MOTIVATION, DRIVE, AND TIME, RATHER THAN SMALL VARIATIONS IN INTELLIGENCE, MIGHT BE THE IMPORTANT DETERMINERS FOR LEARNING IN ADULTS. (DOCUMENT INCLUDES 22 REFERENCES, FIVE CHARTS, AND A BRIEF RESEARCH REVIEW.) THIS DOCUMENT IS CHAPTER 8 OF "ANALYSIS OF CONCEPT LEARNING," PUBLISHED BY ACADEMIC PRESS, 111 FIFTH AVENUE, NEW YORK, NEW YORK 10003, IN 1966, FOR $8.50. (LY)