First-borns might score higher on measures of intelligence, because, at some point in their lives, they were only children who were the sole recipients of their parents' attention.
This idea is supported by earlier research showing that only children older than five make confused judgments about the order of sensations felt on their hands when they are crossed.
It's not only children who display this kind of reaction to rewards, though, subsequent studies have shown a similar effect in all sorts of different populations, many of them grown-ups.
We can have another one, she had said, sitting beside him on the bed as he lay there with his ankles crossed and tears streaming down the sides of his face.
Smith's parents have had to hospitalize her four times with bronchitis since they moved into the trailer a year ago and they say they are sure the trailer is to blame for her illnesses.
Children who get a good education in non-discriminatory behavior will be able to teach others including their own children and eventually stop it all together.