填空题

There are two factors which determine an individual’s intelligence. The first is the (36) of brain he is born with. Human brains differ (37) , some being more capable than others. But no matter how good a brain he has to begin with, an (38) will have a low order of intelligence unless he has (39) to learn. So the second factor is the sort of environment in which he is (40) . If an individual is handicapped environmentally, it is likely that his brain will (41) to develop and he will never attain the level of intelligence of which he is (42) . The importance of environment in determining an individual’s intelligence can be demonstrated by the case history of the (43) twins, Peter and Mark. Being identical, the twins had identical brains at birth. And their growth processes were the same. When the twins were three months old, their parents died, and they were placed in separate foster homes. (44) Mark was reared in the home of well-to-do parents who had been to college. He was read to as a child, sent to good schools, and given every opportunity to be stimulated intellectually. (45) . Mark’s I. Q was 125, twenty-five points higher than the average and fully forty points higher than his identical brother. (46) .