Maté’s first book, Scattered Minds, is about ADD (Attention Deficit Disorder), which increases the risk of addiction. Maté himself suffers from ADD. This disturbs him because, despite decades of scientific research, the role of the environment in brain development, including the relationship between the environment and ADD, doesn’t receive enough attention. He states:

Brain development in the uterus and during childhood is the single most important biological factor in determining whether or not a person will be predisposed to substance dependence and to addictive behaviors of any sort (188).

Out of all the mammals, humans have the least mature brain at birth. Maté considers this a compensation for the benefits bestowed by a larger human brain later in life. He calls the “dynamic process by which the brain’s circuitry is wired after birth” (191) neural Darwinism. The brain of an infant has more neuron connections than it needs. Survival of neuronal connections is a function of cues from the environment. Experience allows some connections to remain in the brain and thrive, and others die off.

Favorable circumstances lead to what Maté calls good stimulation for the brain. A brain that is forming under stressful or neglectful circumstances will have a deficiency of good stimulation.