TWO SERIES OF STUDIES WHOSE SUBJECTS WERE EITHER HOODED AND ALBINO RATS OR YOUNG CHILDREN INVESTIGATED THE INFLUENCE OF EARLY EXPERIENCES ON LATER BEHAVIOR. IN THE FIRST, BOTH SUBSPECIES OF RATS WERE EXPOSED TO EITHER ENRICHED OR RESTRICTED ENVIRONMENTS TO ASSESS THEIR PROBLEM-SOLVING ABILITIES UNDER VARIOUS LEARNING CONDITIONS. THE RESULTS SUGGESTED THAT EARLY ENRICHED EXPERIENCES WILL HELP DEVELOP THE USEFUL CHARACTERISTICS THAT THE ORGANISM ORDINARILY EMPLOYS. WHEN THIS DEVELOPMENT IS INHIBITED, HIERARCHICALLY LOWER CHARACTERISTICS WILL EMERGE MORE PROMINENTLY. THE RESULTS REINFORCED THE IDEA OF GENETIC LIMITATION BUT SUGGESTED THAT THERE IS A WIDE VARIATION OF DEVELOPMENT IN THE ORGANISM WHICH DEPENDS ON ITS EARLY LIFE EXPERIENCES. IN ONE OF THE REINFORCEMENT STUDIES ON YOUNG CHILDREN, IN WHICH A "SUPER- PLAYPEN" ROOM WITH NINE SETS OF MANIPULANDA WAS USED, THE PERFORMANCE OF MIDDLE-CLASS 4-YEAR-OLDS WAS COMPARED TO THAT OF LOWER-CLASS NEGROES. BOTH GROUPS LEARNED THE DISCRIMINATIONS BUT THE MIDDLE-CLASS STUDENTS LEARNED FASTER AND MORE STABLY ALTHOUGH BY THE END OF THE EXPERIMENT THE LOWER CLASS GROUP HAD CAUGHT UP IN RATE AND LEVEL OF CORRECTNESS. THE STUDIES INDICATED THAT DIFFERENCES IN EXPERIMENTAL SUBJECTS ARE AS IMPORTANT IN HUMANS AS THEY ARE IN LOWER ANIMALS IN INVESTIGATIONS OF THE POSSIBLE PROFIT THAT CAN BE OBTAINED FROM EARLY EXPOSURE. STUDIES OF THE LONG-TERM EFFECTS OF ENRICHMENT INTERVENTION WERE RECOMMENDED. THIS PAPER WAS PRESENTED AT THE ANNUAL INVITATIONAL CONFERENCE ON URBAN EDUCATION (4TH, YESHIVA UNIVERSITY, APRIL 26, 1965). (NH)