What Is Intelligence?

What makes some brains smarter than others? Are intelligent people better at storing and retrieving memories? Or perhaps their neurons have more connections allowing them to creatively combine dissimilar ideas?

Einstein said, "The true sign of intelligence is not knowledge but imagination." Socrates said, "I know that I am intelligent, because I know that I know nothing." For centuries, philosophers have tried to pinpoint the true measure of intelligence. More recently, neuroscientists have entered the debate, searching for answers about intelligence from a scientific perspective: What makes some brains smarter than others? Are intelligent people better at storing and retrieving memories? Or perhaps their neurons have more connections allowing them to creatively combine dissimilar ideas? How does the firing of microscopic neurons lead to the sparks of inspiration behind the atomic bomb? Or to Oscar Wilde's wit?


Uncovering the neural networks involved in intelligence has proved difficult because, unlike, say, memory or emotions,  there isn't even a consensus as to what constitutes intelligence in the first place. It is widely accepted that there are different types of intelligence—analytic, linguistic, emotional, to name a few—but psychologists and neuroscientists disagree over whether these intelligences are linked or whether they exist independently from one another.

The 20th century produced three major theories on intelligence. The first, proposed by Charles Spearman in 1904, acknowledged that there are different types of intelligence but argued that they are all correlated—if people tend do well on some sections of an IQ test, they tend to do well on all of them, and vice versa. So Spearman argued for a general intelligence factor called "g," which remains controversial to this day. Decades later, Harvard psychologist Howard Gardner revised this notion with his Theory of Multiple Intelligences, which set forth eight distinct types of intelligence and claimed that there need be no correlation among them; a person could possess strong emotional intelligence without being gifted analytically. Later in 1985, Robert Sternberg, the former dean of Tufts, put forward his Triarchic Theory of Intelligence, which argued that previous definitions of intelligence are too narrow because they are based solely on intelligences that can be assessed in IQ test. Instead, Sternberg believes types of intelligence are broken down into three subsets: analytic, creative, and practical. 

Dr. Gardner sat down with Big Think for a video interview and told us more about his Theory of Multiple Intelligences. He argues that these various forms of intelligence wouldn't have evolved if they hadn't been beneficial at some point in human history, but what was important in one time is not necessarily important in another. "As history unfolds, as cultures evolve, of course the intelligences which they value change," Gardner tells us. "Until a hundred years ago, if you wanted to have h igher education, linguistic intelligence was important. I teach at Harvard, and 150 years ago, the entrance exams were in Latin, Greek and Hebrew. If, for example, you were dyslexic, that would be very difficult because it would be hard for you to learn those languages, which are basically written languages." Now, mathematical and emotional intelligences are more important in society, Gardner says: "While your IQ, which is sort of language logic, will get you behind the desk, if you don’t know how to deal with people, if you don't know how to read yourself, you’re going to end up just staying at that desk forever or eventually being asked to make room for somebody who does have social or emotional intelligence."

Big Think also interviewed Dr. Daniel Goleman, author of the bestselling "Emotional Intelligence," and spoke with him about his theory of emotional intelligence, which comprises four major poles: self-awareness, self-management, social awareness, and relationship management.

Takeaway

Conflicts about the nature of intelligence have hampered studies about its neurobiological underpinnings for years. Yet neuroscientists Rex Jung and Richard Haier may have found a way around this impasse. They published a study in 2007 that reviewed 37 different neuro-imaging studies of IQ (each with a different definition of intelligence) in an attempt to locate what parts of the brain were involved. As it turns out, regardless of the definition used, the results were very similar, enough so that they were able to map a network of brain areas associated with increased IQ scores. Known as the Parieto-Frontal Integration Theory, this model has been gaining momentum among neuroscientists. Earlier this year a team of researchers from Caltech, the University of Iowa, and USC surveyed the IQ test results from 241 brain-lesion patients. Comparing the locations of the brain lesion to their scores on the tests, they were able to discover which parts of the brain were associated with different types of intelligence. And their findings were very much in line with this parieto-frontal integration theory.   

More Resources

— "The Parieto-Frontal Integration Theory (P-FIT) of intelligence," (2007) published by Jung and Haier in the journal Behavioral and Brain Sciences [PDF]

Sternberg's proposal for a pedagogy that acknowledges his triarchic model of intelligence [PDF]

Scientific survey of biological and genetic studies of neural underpinnings of intelligence [PDF]

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Homo sapiens have been on earth for 200,000 years — give or take a few ten-thousand-year stretches. Much of that time is shrouded in the fog of prehistory. What we do know has been pieced together by deciphering the fossil record through the principles of evolutionary theory. Yet new discoveries contain the potential to refashion that knowledge and lead scientists to new, previously unconsidered conclusions.

A set of 8-million-year-old teeth may have done just that. Researchers recently inspected the upper and lower jaw of an ancient European ape. Their conclusions suggest that humanity's forebearers may have arisen in Europe before migrating to Africa, potentially upending a scientific consensus that has stood since Darwin's day.

Rethinking humanity's origin story

The frontispiece of Thomas Huxley's Evidence as to Man's Place in Nature (1863) sketched by natural history artist Benjamin Waterhouse Hawkins. (Photo: Wikimedia Commons)

As reported in New Scientist, the 8- to 9-million-year-old hominin jaw bones were found at Nikiti, northern Greece, in the '90s. Scientists originally pegged the chompers as belonging to a member of Ouranopithecus, an genus of extinct Eurasian ape.

David Begun, an anthropologist at the University of Toronto, and his team recently reexamined the jaw bones. They argue that the original identification was incorrect. Based on the fossil's hominin-like canines and premolar roots, they identify that the ape belongs to a previously unknown proto-hominin.

The researchers hypothesize that these proto-hominins were the evolutionary ancestors of another European great ape Graecopithecus, which the same team tentatively identified as an early hominin in 2017. Graecopithecus lived in south-east Europe 7.2 million years ago. If the premise is correct, these hominins would have migrated to Africa 7 million years ago, after undergoing much of their evolutionary development in Europe.

Begun points out that south-east Europe was once occupied by the ancestors of animals like the giraffe and rhino, too. "It's widely agreed that this was the found fauna of most of what we see in Africa today," he told New Scientists. "If the antelopes and giraffes could get into Africa 7 million years ago, why not the apes?"

He recently outlined this idea at a conference of the American Association of Physical Anthropologists.

It's worth noting that Begun has made similar hypotheses before. Writing for the Journal of Human Evolution in 2002, Begun and Elmar Heizmann of the Natural history Museum of Stuttgart discussed a great ape fossil found in Germany that they argued could be the ancestor (broadly speaking) of all living great apes and humans.

"Found in Germany 20 years ago, this specimen is about 16.5 million years old, some 1.5 million years older than similar species from East Africa," Begun said in a statement then. "It suggests that the great ape and human lineage first appeared in Eurasia and not Africa."

Migrating out of Africa

In the Descent of Man, Charles Darwin proposed that hominins descended out of Africa. Considering the relatively few fossils available at the time, it is a testament to Darwin's astuteness that his hypothesis remains the leading theory.

Since Darwin's time, we have unearthed many more fossils and discovered new evidence in genetics. As such, our African-origin story has undergone many updates and revisions since 1871. Today, it has splintered into two theories: the "out of Africa" theory and the "multi-regional" theory.

The out of Africa theory suggests that the cradle of all humanity was Africa. Homo sapiens evolved exclusively and recently on that continent. At some point in prehistory, our ancestors migrated from Africa to Eurasia and replaced other subspecies of the genus Homo, such as Neanderthals. This is the dominant theory among scientists, and current evidence seems to support it best — though, say that in some circles and be prepared for a late-night debate that goes well past last call.

The multi-regional theory suggests that humans evolved in parallel across various regions. According to this model, the hominins Homo erectus left Africa to settle across Eurasia and (maybe) Australia. These disparate populations eventually evolved into modern humans thanks to a helping dollop of gene flow.

Of course, there are the broad strokes of very nuanced models, and we're leaving a lot of discussion out. There is, for example, a debate as to whether African Homo erectus fossils should be considered alongside Asian ones or should be labeled as a different subspecies, Homo ergaster.

Proponents of the out-of-Africa model aren't sure whether non-African humans descended from a single migration out of Africa or at least two major waves of migration followed by a lot of interbreeding.

Did we head east or south of Eden?

Not all anthropologists agree with Begun and his team's conclusions. As noted by New Scientist, it is possible that the Nikiti ape is not related to hominins at all. It may have evolved similar features independently, developing teeth to eat similar foods or chew in a similar manner as early hominins.

Ultimately, Nikiti ape alone doesn't offer enough evidence to upend the out of Africa model, which is supported by a more robust fossil record and DNA evidence. But additional evidence may be uncovered to lend further credence to Begun's hypothesis or lead us to yet unconsidered ideas about humanity's evolution.