Many like to point out that performance on intelligence tests is actually more indicative of social upbringing, general health, aptitude to testing, education level, and so on. Things that aren’t intelligence, in other words. So the tests may be useful, but not for what they’re intended.
It’s not all doom and gloom. Scientists aren’t ignorant of these criticisms and are a resourceful bunch. Today, intelligence tests are more useful—they provide a wide range of assessments (spatial awareness, arithmetic etc.), rather than one general assessment, and this gives us a more robust and thorough demonstration of ability. Studies have shown that performance on intelligence tests also seems to remain fairly stable over a person’s lifetime despite all the changes or learning they experience, so they must be detecting some inherent quality rather than just random circumstance.1
So, now you know what we know, or what we think we know. One of the generally accepted signs of intelligence is an awareness and acceptance of what you don’t know. Good job.
Where are your trousers, professor?
(How intelligent people end up doing stupid things)
The stereotype of an academic is a white-haired white-coated chap (it’s almost always a man) in late middle age, talking quickly and often about his field of study while being utterly clueless about the world around him, effortlessly describing the fruit fly genome while absent-mindedly buttering his tie. Social norms and day-to-day tasks are completely alien and baffling to him; he knows everything there is to know about his subject, but little to nothing beyond that.
Being intelligent isn’t like being strong; a strong person is strong in every context. However, someone brilliant in one context can seem like a shuddering dunce in another.
This is because intelligence, unlike physical strength, is a product of the never uncomplicated brain. So what are the brain processes that underpin intelligence, and why is it so variable? Firstly, there is ongoing debate in psychology about whether or not humans use a single intelligence, or several different types. Current data suggests it is probably a combination of things.
A dominant view is that there is a single property that underpins our intelligence, which can be expressed in varying ways. This is often known as “Spearman’s g,” or just g. Named after Charles Spearman, a scientist who did a great service for intelligence research and science in general in the 1920s by developing factor analysis. The previous section revealed how IQ tests are commonly used despite certain reservations; factor analysis is something that makes them (and other tests) useful.
Factor analysis is a mathematically dense process but what you need to know is that it is a form of statistical decomposition. This is where you take large volumes of data (for example, those produced by IQ tests) and mathematically break them down in various ways and look for factors connecting or influencing the results. These factors aren’t known beforehand, but factor analysis can flush them out. If students at a school got mediocre grades overall on their tests, the principal might want to see exactly how the grades were achieved in more detail. Factor analysis could be used to assess the information from all the test scores and take a closer look. It could reveal that math questions were generally answered well, but history questions were answered poorly. The principal can then feel justified about yelling at the history teachers for wasting time and money (although he probably isn’t justified, given the many possible explanations for poor results).
Spearman used a process similar to this to assess IQ tests and discovered that there was seemingly one underlying factor that underpinned test performance. This was labeled the single general factor, g, and if there’s anything in science that represents what your everyday person would think of as intelligence, it’s g.
It would be wrong to say that g = all possible intelligence, as intelligence can manifest in so many ways. It’s more a general “core” of intellectual ability. It’s viewed as something like the foundations and frame of a house. You can add extensions and furniture, but if the underlying structure isn’t strong enough it’ll be futile. Similarly, you can learn all the big words and memory tricks you like, but if your g isn’t up to scratch you won’t be able to do much with them.
Research suggests there might be a part of the brain that is responsible for g. Chapter 2 discussed short-term memory in detail and alluded to the term “working memory.” This refers to the actual processing and manipulation, the “using” of the information in short-term memory. In the early 2000s, Professor Klaus Oberauer and his colleagues ran a series of tests and found that a subject’s performance on working-memory tests corresponded strongly with tests to determine his or her g, indicating that a person’s working-memory capacity is a major factor in overall intelligence.2 Ultimately, if you score high on a working-memory task, you’re very likely to score high on a range of IQ tests. It makes logical sense; intelligence involves obtaining, retaining and using information as efficiently as possible, and IQ tests are designed to measure this. But such processes are basically what the working memory is for.
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 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 crystallized intelligence.