Intelligence research has been the domain of psychology and sociology and barely intersects with neuroscience. Yet intelligence has everything to do with the brain, and integrating these fields into a common framework is essential.
Taking on Intelligence
The study of intelligence has its roots in the 1800s with the polymath Francis Galton, and the publication of the Origin of Species by his cousin Charles Darwin. On reading Origin of Species Galton wrote to Darwin that:
I have laid it down in the full enjoyment of a feeling that one rarely experiences after boyish days, of having been initiated into an entirely new province of knowledge, which, nevertheless, connects itself with other things in a thousand ways.
Darwin’s work, demonstrating that particular features could be selectively bred and were therefore inherited, was focused around plants and animals. Galton wondered whether this could apply to man’s intellect as well, leading to a several decades long inquiry centered on the question of whether intelligence, like physical traits, were inherited or created. It was he who coined the term nature versus nurture.
An obvious challenge at the time was that there was yet no ‘measure’ of intelligence of any kind. As a proxy Galton considered ‘noteworthy accomplishments’ that were thought to be inherently intelligent. But what is a noteworthy accomplishment that is inherently ‘intelligent’? Galton eliminated nobility, legislature and army from the study where he states that social position and class took precedence over able intellect. Instead he focused on the fields of science, literature, music and law where he believed intellect dominated. Using lists of noteworthy people he found that anywhere from 1 in 3 to 1 in 7 people have male relatives who are also noteworthy, he found. An exceptionally high number when considering the size of the population at large. This led Galton to the conclusion that intelligence was likely an inherited trait. Based just on his evidence, alternative explanations are plenty. Nonetheless, it was the first probing of its kind and culminated in a book titled ‘Hereditary Genius’ published in 1869.
The idea that intelligence could potentially be hereditary was novel. On reading it Darwin penned a letter to Galton in which he wrote:
I have only read about 50 pages of your book (to the Judges), but I must exhale myself, else something will go wrong in my inside. I do not think I ever in all my life read anything more interesting and original… You have made a convert of an opponent in one sense, for I have always maintained that, excepting fools, men did not differ much in intellect, only in zeal and hard work; and I still think this is an eminently important difference.
150 years of Intelligence Research
It has been 150 years since then and the field of intelligence research has grown in two directions. The first has been in the development of methods of measuring intelligence or IQ. This began with Spearman’s idea of g or a general mental energy and the Binet-Simon scales developed at the turn of the century to stream French children entering primary school. This was followed by development of the Stanford-Binet IQ tests and subsequently the Wechsler Intelligence scales. Recent years have given way to ideas around multiple intelligences and emotional intelligence. Debates still rage over what is a valid measure of intelligence.
The second major area of research and debate has been about the role of genes and environment in intelligence. Since Galton’s early inquiry, many have joined the debate. From Jensen’s equations and explanations that left little to environment, and Flynn’s studies that demonstrate a greater environmental component, this has been a field fraught with controversy and emotion. Gene’s matter, so does environment, but how, and by how much?
The Brain and Intelligence
Missing in large part from these debates is the neuroscience community. Intelligence is about the brain, and yet our understanding of how the physiology of the brain gives rise to intelligence is nascent. A small group of researchers have sought to find links using brain imaging. For example, relationships have been found between intelligence and glucose metabolism with PET, the connectivity of white matter tracts using diffusion tensor imaging, and the overall integration of the brain using fMRI.
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However, aside from some small pockets of research, the neuroscience community has taken its own direction (the EEG field is conspicuous in its paucity of intelligence research). Few neuroscientists will speak of intelligence in the same language or constructs as the Intelligence research community, who are largely from psychology or sociology. Rather neuroscientists have different cognitive constructs and are more likely to speak of Executive Function rather than intelligence. Executive Function is a concept developed around the idea of self-control and inhibition that can enable attention and focus on a task at hand. Without a common language or framework, however, it is difficult to make the links between such understanding of the brain and intelligence.
The lack of integration of these fields is unfortunate since it ultimately hinders our ability to move forward. Yet integration of these fields is crucial. At a societal level the most important questions rest around what gives rise to intelligence, and what the drivers are at the level of brain physiology. It is not until we really understand what those are that we can really change outcomes.
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