Studies have found the heritability of IQ to be between 0.7 and 0.8 in adults and 0.45 in childhood in the United States. It may seem reasonable to expect that genetic influences on traits like IQ should become less important as one gains experiences with age. However, that the opposite occurs is well documented. Heritability measures in infancy are as low as 0.2, around 0.4 in middle childhood, and as high as 0.8 in adulthood. Everyday experience would suggest that as people grow older, they get to know themselves better. They choose, if they can, jobs and activities which make the most of their abilities. The effect of this would be to show a closer fit between their genetics and their environment.