A dramatic illustration of how environment shapes personality is the story of the Gilmore family. On January 17, 1978, in Utah, the convicted double murderer Gary Gilmore was executed by firing squad, his unyielding refusal to appeal his death sentence having gained him a measure of international notoriety. The shattering story of his childhood, blighted by family violence, alcoholism and spite was chronicled later by his brother Mikal Gilmore in the memoir Shot in the Heart. Mikal, the youngest of four boys, was born when Gary was eleven years old. If children reared in the same family shared the same environment, the differences between siblings would have to be due to genetic inheritance. In the case of the Gilmores, it is easy to see why Mikal, born at a time when the family was enjoying a period of relative stability, would feel he had been brought up in a different world, why the misery of his childhood, as he put it, had been so radically different from the misery of his brothers' childhood. Even without such vast chasms in experience, the environment of siblings is never the same. Environment has far greater impact on the structures and circuits of the human brain than was realized even a decade ago. It is what shapes the inherited genetic material. I believe it to be the decisive factor in determining whether the impairments of ADD will or will not appear in a child. Many variables will influence the particular environment a child experiences. Birth order, for one, automatically places siblings in dissimilar situations. The older sibling has to suffer the pain of seeing parental love and attention directed toward an intruder. The younger sibling may need to learn survival in an environment that harbors a stronger, potentially hostile rival, and never comes to know either the special status or the burden of being an only child. The full weight of unconscious parental expectations is far more likely to fall on the firstborn. Historical studies of birth order have established it as an important influence on the shaping of the personality, comparable with sex.