“Neurobiology of Intelligence: Science and Ethics”, 2004-06 (; backlinks):
Intelligence research is more advanced and less controversial than is generally realized. Definitive conclusions about the neural and genetic bases of intelligence are being drawn—these have ethical implications that need to be addressed.
General intelligence and volume of frontal grey matter (assessed by magnetic resonance imaging) are correlated.
The lateral prefrontal cortex is consistently activated during intelligence testing. Frontal and parietal brain regions implicated in working memory are also activated under test conditions. These data contribute to the debate on whether intelligence has a unitary (activation of a single brain region/functional unit) or multiple basis.
The structure of brain regions that influence intelligence is under strong genetic control. Studies of intelligence using twins reared separately support the heritability of cognitive function.
Environmental factors—such as prenatal exposure to toxins, duration of breastfeeding and shared family environment—affect intellectual function. These non-genetic factors have a much greater effect on childhood intelligence in impoverished families.
Establishing a neurobiological basis for intelligence has important ethical implications. For example, is it ethical to assess racial differences in intelligence? Such questions need to be proactively addressed so that the field of intelligence research is not perceived as socially divisive.
Human mental abilities, such as intelligence, are complex and profoundly important, both in a practical sense and for what they imply about the human condition. Understanding these abilities in mechanistic terms has the potential to facilitate their enhancement. There is strong evidence that the lateral prefrontal cortex, and possibly other areas, support intelligent behavior. Variations in intelligence and brain structure are heritable, but are also influenced by factors such as education, family environment and environmental hazards. Cognitive, psychometric, genetic and neuroimaging studies are converging, and the emergence of mechanistic models of intelligence is inevitable. These exciting scientific advances encourage renewed responsiveness to the social and ethical implications of conducting such research.