Status Updates From The Neuroscience of Intelli...

Adolescents from more affluent families tend to be brighter because their parents are brighter, not because they enjoy better family environments

Higher income allows upward mobility, especially the ability to move from poor environments to better ones. This often includes better schools and more resources to foster children’s development so that children now have many advantages. If the children have high intelligence and greater academic and economic success, it could be concluded that higher parental intelligence was the key factor driving this chain of eve

Efficient information flow, through whichever subnetworks are relevant for an individual, was hypothesized to relate to high g, and subnetworks of the PFIT were hypothesized to relate to a person’s pattern of mental ability strengths and weaknesses.

Very rapid sequential images can show regional blood flow as a function of hemoglobin determinations and blood flow is an indirect measure of neuron activity. The more a brain area is active, the more blood flows to it. It is functional MRI (fMRI) that has been used widely in cognitive neuroscience to show brain activity during specific cognitive tasks.

Intelligence test scores are related to brain glucose metabolism. This helps validate that the test scores were not meaningless numbers representing a statistical artifact. In fact, as neuroimaging studies of intelligence continue to increase, old criticisms about intelligence test scores having no meaning are less and less meaningful, if they were ever meaningful at all

men and women were equally matched on SAT-Math score, and they solved the same problems during the scan equally well. Their brains, however, showed apparently different patterns of activity.

this counter-intuitive result suggested to us that it’s not how hard your brain works that makes you smart, it’s how efficiently it works. Based on this result, we proposed the brain efficiency hypothesis of intelligence: higher intelligence requires less brainwork. About the same time, another group reported inverse correlations in multiple areas of the cortex between GMR and scores on a test of verbal fluency

Brain activity assessed with PET during Raven’s Test. Red and yellow show greatest activity in units of glucose metabolic rate. The person with the highest test score shows lower brain activity during the test, consistent with brain efficiency related to intelligence

Because the brain is soft tissue, X-rays pass through easily and brain pictures are not very detailed. By contrast, PET can quantify brain activity as glucose metabolism, blood flow, or in some cases, neurotransmitter activity. This is accomplished in a conceptually simple way. Radioactive tracers are injected into a person while they perform a cognitive task and the brain areas that are most active during the task

Based on cross-sectional data, in young twins 4-6 years old, the heritability of intelligence estimate is about 40%, and the heritability rises to a high of about 85% when the twins are older adults. In other words, the genetic influences on intelligence variance actually increase with age and environmental influences decrease

twin studies done by different investigators around the world with large samples arrive at an average value for the correlation of intelligence scores among identical twins raised apart of .75 (Plomin & Petrill, 199' ). Burt’s value was .77. For comparison, based on 19 studies ranging in sample sizes between 26 and 1,300 identical twin pairs, the average value for identical twins raised together is about .86

The bias hypothesis, as noted in the previous chapter , has been studied extensively and has little empirical support.

Moreover, in the next two chapters, neuroimaging shows that intelligence test scores are correlated to a variety of structural and functional measures of the brain; findings that would be impossible if the test scores were meaningless