by Dean Burnett
Scanning studies and investigations of people with brain injuries provide compelling evidence for a pivotal role of the prefrontal cortex in processing both g and working memory, with those afflicted with frontal-lobe injury demonstrating a wide range of unusual memory problems, typically traced back to a deficit in working memory, thus further implying a large overlap between the two things. This prefrontal cortex is the right behind the forehead, the beginning of the frontal lobe that is regularly implicated in higher ‘executive’ functions such as thinking, attention and consciousness.
But working memory and g are not the whole story. Working-memory processes mostly work with verbal information, supported by words and terms we could speak aloud, like an internal monologue. Intelligence, on the other hand, is applicable to all types of information (visual, spatial, numerical …), prompting researchers to look beyond g when trying to define and explain intelligence.
Raymond Cattell (a former student of Charles Spearman) and his student John Horn devised newer methods of factor analysis and identified two types of intelligence in studies spanning the 1940s to 1960s; fluid intelligence and crystallised intelligence.
Fluid intelligence is the ability to use information, work with it, apply it, and so on. Solving a Rubik’s cube requires fluid intelligence, as does working out why your partner isn’t talking to you when you have no memory of doing anything wrong. In each case, the information you have is new and you have to work out what to do with it in order to arrive at an outcome that benefits you.
Crystallised intelligence is the information you have stored in memory and can utilise to help you get the better of situations. Knowing the lead actor in an obscure 1950s film for a pub quiz requires crystallised intelligence. Knowing all the capital cities of the northern hemisphere is crystallised intelligence. Learning a second (or third or fourth) language utilises crystallised intelligence. Crystallised intelligence is the knowledge you have accumulated, where fluid intelligence is how well you can use it or deal with unfamiliar things that need working out.
It’s fair to say that fluid intelligence is another variation of g and working memory; the manipulation and processing of information. But crystallised intelligence is increasingly viewed as a separate system, and the workings of the brain back this up. One quite telling fact is that fluid intelligence declines as we age; someone aged eighty will perform worse on a fluid intelligence test than he or she did aged thirty, or fifty. Neuroanatomical studies (and numerous autopsies) revealed the prefrontal cortex, believed responsible for fluid intelligence, atrophies more with age than most other brain regions.
Contrastingly, crystallised intelligence remains stable over a lifetime. Someone who learns French at eighteen will still be able to speak it at eighty-five, unless they stopped using it and forgot it at nineteen. Crystallised intelligence is supported by long-term memories, which are distributed widely throughout the brain and tend to be resilient enough to withstand the ravages of time. The prefrontal cortex is a demanding energetic region that needs to engage in constant active processing to support fluid intelligence, actions that are quite dynamic and thus more likely to result in gradual wear and tear (intense neuronal activity tends to give off a lot of waste products such as free radicals, energetic particles that are harmful to cells).
Both types of intelligence are interdependent; there’s no point in being able to manipulate information if you can’t access any of it, and vice versa. It’s tricky to separate them clearly for study. Luckily, intelligence tests can be designed to focus mostly on either fluid or crystallised intelligence. Tests that require individuals to analyse unfamiliar patterns and identify odd ones out or work out how they are interconnected are thought to assess fluid intelligence; all the information is novel and needs to be processed, so crystallised-intelligence use is minimal. Similarly, tests of recall and knowledge such as word-list memory, or the aforementioned pub quizzes, focus on crystallised intelligence.
It’s never quite that simple of course. Tasks where you have to sort unfamiliar patterns still rely on an awareness of images, colours, even the means by which you complete the test (if it’s rearranging a series of cards, you’ll be using your knowledge of what cards are and how to arrange them). This is another thing that makes brain-scanning studies tricky; even doing a simple task involves multiple brain regions. But, in general, tasks for fluid intelligence tend to show greater activity in the prefrontal cortex and associated regions, and crystallised intelligence tasks suggest a role of the wider cortex, often the parietal-lobe (the upper-middle bit of the brain) regions, such as the supramarginal gyrus and Broca’s area. The former is often thought of as being necessary for storage and processing of information concerning emotion and some sensory data, while the latter is a key part of our language-processing system. Both are interconnected, and suggest functions requiring access to long-term memory data. While it’s still not clear cut, there’s mounting evidence to support this fluid/crystallised distinction of general intelligence.
Miles Kingston captures the theory brilliantly: ‘Knowledge is knowing that a tomato is a fruit; wisdom is not putting it in a fruit salad.’ It requires crystallised intelligence to know how a tomato is classed, and fluid intelligence to apply this information when making a fruit salad. You might now think that fluid intelligence sounds a lot like common sense. Yes, that would be another example. But, for some scientists, two distinct types of intelligence are still not enough. They want more.
The logic is that a single general intelligence is insufficient for explaining the wide variety of intellectual abilities humans can demonstrate. Consider footballers – they often didn’t thrive academically, but being able to play a complicated sport like football at professional level requires a great deal of intellectual ability such as precise control, calculating force and angles, spatial awareness of a wide area, and so on. Concentrating on your job while filtering out the rantings of the obsessive fans takes considerable mental fortitude. The common concept of ‘intelligence’ is clearly a bit restrictive.
Perhaps the starkest examples are ‘savants’, individuals with some form of neurological disorder, who show an extreme affinity or ability for complex tasks involving maths, music, memory, etc. In the film Rain Man, Dustin Hoffman plays Raymond Babbit, an autistic but mathematically gifted psychiatric patient. The character was inspired by a real individual called Kim Peek who was dubbed a ‘mega-savant’ for his ability to memorise, to the word, up to twelve thousand books.
These examples and more lead to the development of multiple intelligence theories, because how can someone be both unintelligent in one sphere and a gifted in another if there’s only one type of intelligence? The earliest theory of this nature is probably that put forward by Louis Leon Thurstone in 1938, who proposed that human intelligence was made up of seven Primary Mental Abilities:
Verbal comprehension (understanding words: ‘Hey, I know what that means!’)
Verbal fluency (using language: ‘Come here and say that, you acephalous buffoon!’)
Memory (‘Wait, I remember you, you’re the cage-fighting world champion!’)
Arithmetic ability (‘The odds of me winning this fight are about 82523 to 1.’)
Perceptual speed (spotting and linking details: ‘Is he wearing a necklace made of human teeth?’)
Inductive reasoning (deriving ideas and rules from situations: ‘Any attempt to placate this beast is only going to anger him further.’)
Spatial visualisation (mentally visualising/manipulating a 3D environment: ‘If I tip this table it’ll slow him down and I can dive out that window.’)
Thurstone derived his Primary Mental Abilities after devising his own methods of factor analysis and applying them to IQ test results of thousands of college students.3 However, reanalysis of his results using more traditional factor analysis showed there was a single ability influencing all the tests, rather than several different ones. Basically, he’d discovered g again. This and other criticisms (f
or instance that he studied only college students, hardly the most representative group when it comes to general human intelligence) meant the Primary Mental Abilities weren’t that widely accepted.
Multiple intelligences returned in the 1980s via Howard Gardner, a prominent researcher who proposed that there were several modalities (types) of intelligence, and his aptly titled Theory of Multiple Intelligences, following research into brain-damaged patients who still retained certain types of intellectual abilities.4 His proposed intelligences were similar to Thurstone’s in some ways, but also included musical intelligence, and personal intelligences (ability to interact well with people, and ability to judge your own internal state).
The multiple-intelligence theory has its adherents though. Multiple intelligences are popular largely because it means everyone can potentially be intelligent, just not in the ‘normal’ brainy boffin way. This generalisability is also something it’s criticised for. If everyone is intelligent, the concept itself becomes meaningless in the scientific sense. It’s like giving everyone a medal for showing up at a school sports day; it’s nice that everyone gets to feel good, but it does defeat the point of ‘sport’.
So far, the evidence for the multiple-intelligence theory remains debatable. The data available is widely regarded as being yet more evidence for g or something like it, combined with personal differences and preferences. What this means is that two people who excel, one at music and one at maths, aren’t actually demonstrating two different types of intelligence, but the same general intelligence applied to different types of tasks. Similarly, professional swimmers and tennis players use the same muscle groups to practise their sports; the human body doesn’t have dedicated tennis muscles. Nonetheless, a champion swimmer can’t automatically play top-level tennis. Intelligence is believed to work in similar ways.
Many argue that it is perfectly plausible to have a high g but prefer to utilise and apply it in specific ways, which would manifest as different ‘types’ of intelligence if you look at it in a certain way. Others argue that these supposed different types of intelligence are more suggestive of personal inclinations based on background, tendencies, influences, and so on.
Current neurological evidence still favours the existence of g and the fluid/crystallised set-up. Intelligence in the brain is believed to be due to the way the brain is arranged to organise and coordinate the various types of information, rather than a separate system for each one. This will be covered in more detail later in this chapter.
We all direct our intelligence in certain ways and directions, whether due to preference, upbringing, environment or some underlying bias imparted by subtle neurological properties. This is why you get supposedly very smart people doing things we’d consider daft; it’s not that they aren’t clever enough to know better, it’s that they’re too focused elsewhere to care. On the plus side, this probably means it’s OK to laugh at them, as they’ll be too distracted to notice.
Empty vessels make the most noise
(Why intelligent people can often lose arguments)
One of the most infuriating experiences possible is arguing with someone who’s convinced they’re right when you know full well that they’re wrong, and can prove they’re wrong with facts and logic, but still they won’t budge. I once witnessed a blazing row between two people, one of whom was adamant that this is the twentieth century, not the twenty-first, because, ‘It’s twenty fifteen? Duh!’ That was their actual argument.
Contrast this with the psychological phenomenon known as ‘impostor syndrome’. High achievers in many fields persistently underestimate their abilities and achievements despite having actual evidence of these things. There are many social elements to this. For instance, it’s particularly common in women who achieve success in a traditionally male-dominated environment (aka most of them) so they are likely to be influenced by stereotyping, prejudice, cultural norms and so on. But it’s not limited to women, and one of the more interesting aspects is that it predominately affects high achievers – those people with a typically high level of intelligence.
Guess which scientist said this shortly before his death: ‘The exaggerated esteem in which my lifework is held makes me very ill at ease. I feel compelled to think of myself as an involuntary swindler.’
Albert Einstein. Not exactly an underachiever.
These two traits, impostor syndrome in intelligent people and illogical self-confidence in less intelligent people, regularly overlap in unhelpful ways. Modern public debate is disastrously skewed due to this. Important issues such as vaccination or climate change are invariably dominated by the impassioned rantings of those who have uninformed personal opinions rather than the calmer explanations of the trained experts, and it’s all thanks to a few quirks of the brain’s workings.
Basically, people rely on other people as a source of information and support for their own views/beliefs/sense of self-worth, and Chapter 7 on social psychology will go into this in more detail. But, for now, it seems the more confident a person is, the more convincing they are and the more others tend to believe the claims they make. This has been demonstrated in a number of studies, including those conducted in the 1990s by Penrod and Custer, who focused on courtroom settings. These studies looked at the degree to which jurors were convinced by witness testimonies and found that jurors were far more likely to favour witnesses who came across as confident and assured than those who seemed nervous and hesitant or unsure of the details of their claim. This was obviously a worrying finding; the content of a testimony being less influential in determining a verdict than the manner in which it is delivered could have serious ramifications for the justice system. And there’s nothing to say it’s limited to a courtroom setting; who’s to say politics isn’t similarly influenced?
Modern politicians are media-trained so they can speak confidently and smoothly on any subject for prolonged periods without saying anything of value. Or worse, something downright stupid like, ‘They misunderestimated me’ (George W. Bush), or, ‘Most of our imports come from overseas’ (George W. Bush again). You’d assume that the smartest people would end up running things; the smarter a person is, the better job they’d be able to do. But as counterintuitive as it may seem, the smarter a person is, the greater the odds of them being less confident in their views, and the less confident they come across as being, the less they’re trusted. Democracy, everyone.
Intelligent sorts may be less confident because there can often be a general hostility to those of the intellectual persuasion. I’m a neuroscientist by training, but I don’t tell people this unless directly asked, because I once got the response, ‘Oh, think you’re clever, do you?’
Do other people get this? If you tell someone you’re an Olympic sprinter, does anyone ever say, ‘Oh, think you’re fast, do you?’ This seems unlikely. But, regardless, I still end up saying things like, ‘I’m a neuroscientist, but it’s not as impressive as it sounds.’ There are countless social and cultural reasons for anti-intellectualism, but one possibility is that it’s a manifestation of the brain’s egocentric or ‘self-serving’ bias and tendency to fear things. People care about their social standing and well-being, and someone seeming more intelligent than them can be perceived as a threat. People who are physically bigger and stronger can certainly be intimidating, but it’s a known property. A physically fit person is easy to understand; they just go to the gym more, or have been doing their chosen sport for far longer, right? That’s how muscles and such work. Anyone could end up like them if they do what they did, if they had the time or inclination.
But someone who is more intelligent than you presents an unknowable quantity, and as such they could behave in ways that you can’t predict or understand. This means the brain cannot work out whether they present a danger or not, and in this situation the old ‘better safe than sorry’ instinct is activated, triggering suspicion and hostility. It’s true that a person could also learn and study to become more intelligent as well, but th
is is far more complex and uncertain than physical improvement. Lifting weights gives you strong arms, but the connection between learning and intelligence is far more diffuse.
The phenomenon of less-intelligent people being more confident has an actual scientific name: the Dunning–Kruger effect. It is named for David Dunning and Justin Kruger of Cornell University, the researchers who first looked into the phenomenon, inspired by reports of a criminal who held up banks after covering his face with lemon juice, because lemon juice can be used as invisible ink, so he thought his face wouldn’t show up on camera.5
Just let that sink in for a moment.
Dunning and Kruger got subjects to complete a number of tests, but also asked them to estimate how well they thought they had done on the tests. This produced a remarkable pattern: those who performed badly on the tests almost always assumed they’d done much much better, whereas those who did well invariably assumed they’d done worse. Dunning and Kruger argued that those with poor intelligence not only lack the intellectual abilities, they also lack the ability to recognise that they are bad at something. The brain’s egocentric tendencies kick in again, suppressing things that might lead to a negative opinion of oneself. But also, recognising your own limitations and the superior abilities of others is something that itself requires intelligence. Hence you get people passionately arguing with others about subjects they have no direct experience of, even if the other person has studied the subject all their life. Our brain has only our own experiences to go from, and our baseline assumptions are that everyone is like us. So if we’re an idiot …