Chapter 6 introduces astonishing neuroscience methods for studying synapses, neurons, circuits, and networks that move intelligence research even deeper into the brain. Soon we might measure intelligence based on brain speed and build intelligent machines based on how the brain works. Collaborative efforts around the world are hunting relevant genes, creating virtual brains, and mapping brain fingerprints unique to individuals that predict intelligence. Overlapping neuro-circuits for intelligence, consciousness, and creativity are explored. Finally, this chapter introduces the terms “neuro-poverty” and “neuro-SES” (social economic status) and explains why neuroscience advances in intelligence research may inform education policies.

Chapter 1 aims to correct popular misinformation and summarizes how intelligence is defined and measured for scientific research. Some of the validity data will surprise you. For example, childhood IQ scores predict adult mortality.

Chapters 3 and 4 delve into neuroimaging and how these revolutionary technologies visualize and measure intelligence in the brain, and indicate the neurobiological mechanisms involved. Twin studies of intelligence, for example, combine neuroimaging and DNA analyses. Key results show common genes for brain structure and intelligence.

Chapter 5 focuses on the enhancement of intelligence. It begins with critiques of widely publicized but incorrect claims about increasing IQ and ends with electrical brain stimulation. So far, there is no proven way to enhance intelligence, but this chapter explores why there is a strong possibility that manipulation of some genes and their biological processes may achieve dramatic increases.

Chapter 2 epigraph the overwhelming evidence that there are major genetic influences on intelligence and its development. Conclusive studies from quantitative and molecular genetics leave no doubt about this. Since genes always work through biological mechanisms, there must be a neurobiological basis for intelligence, even when there are environmental influences on those mechanisms. Polygenic scores based on DNA can predict IQ.

Peter returned to Greiz only once, in 1990 with his family, 44 years after he escaped from the Soviet zone with his stepmother and brothers. On this visit to the home of his childhood memories, the Berlin wall had just fallen but the German reunification was yet to come. East Germany – the German Democratic Republic – had existed as a nation since 1949, having transitioned from being a Soviet-occupied zone to statehood, but of course remaining under heavy Soviet influence. Peter’s visit was to an East Germany that was gradually being disbanded. It was still a communist nation, but citizens of the German Democratic Republic could now travel abroad. Through the centralized East German government, Peter had arranged modest accommodations in the old town area of Greiz, where no direct bookings or modern hotels existed at that time.

Peter arrived as a new assistant professor of pediatric neurology at Yale University in 1966. This was in the midst of the Reye’s syndrome peak of the late 1960s. Reye’s syndrome is a life-threatening pediatric disease characterized by progressive brain and liver damage in children, often after a viral illness. It became a rare condition after epidemiological studies suggested a link between aspirin use in children and the onset of Reye’s syndrome after a viral illness. The reduced rates of Reye’s syndrome are largely attributable to public health messaging to limit aspirin use in children, but until that change, it often fell to pediatric neurologists to keep Reye’s syndrome patients alive.

In the later stages of Parkinson’s disease most patients develop progressive cognitive impairment and dementia. During his final year, Peter often spoke in German. He alternated between disorientation and lucidity. During his disoriented periods, he wandered. At night he would scream out in terror. It became clear that he needed round-the-clock care and, after much hesitation, his family all decided that he needed to live in the care facility connected to Peter and Janellen’s retirement community. The iron grip of Parkinson’s disease is difficult for families. It is a confusing kind of dementia, the periods of lucidity raising hopes that are repeatedly dashed. Peter was locked in during those last months. It was not always clear he recognized his friends or family members, but sometimes he made so much sense! “Ich bin müde” (I am tired) or “genug” (enough), he said.

After completing his undergraduate training at the University of Buffalo in three years, Peter started at Harvard Medical School in 1953, four and a half years after arriving in the United States through Ellis Island. For the first time, Peter was really on his own. As a first-year student Peter moved into Vanderbilt Hall, a dormitory for male Harvard medical students. In the 1950s, the Harvard medical class was largely composed of elite highly educated men, many of whom had attended Harvard College or other Ivy League institutions. By living in Vanderbilt, Peter became fully immersed in an entirely new culture of the American elite.