- [Lecturer] You've probably heard of IQ, which means intelligence quotient, and you may even have
taken an intelligence test, which is supposed to measure
how intelligent you are, but what does intelligence mean? For a term that's used so widely we have kind of a hard time defining it. Does it mean street smarts,
book smarts, creativity? Psychologists, even though they still have some disagreements,
tend to define intelligence as a mental quality, allowing
you to learn from experience, solve problems and use your knowledge to adapt to new situations. Intelligence tests use numerical scores to measure your aptitude
for those types of tasks and compare them to how
well other people do. So if intelligence is made
up of different aptitudes, then is it multiple
abilities or is it just one? One theory is that there's
just one general intelligence. Evidence to support this
theory comes from the fact that people who score really
well on one type of test, such as verbal ability, also
tend to score really well in other types of tests, such as math. Now, you might be better
at one of these categories than the other, relative to yourself, but relative to other people you probably have about the same level
of skills in both areas. The factor underlying
these consistent abilities is referred to as the g factor. You can think of g for
general intelligence. Although there's some good evidence for g, there's also some support for theories of multiple intelligences. A psychologist named Robert Sternberg proposed a theory of three
main types of intelligence, analytical intelligence,
what we might think of as academic abilities or the ability to solve well-defined problems, creative intelligence, the
ability to react adaptively to new situations and
to generate novel ideas, and practical intelligence, the ability to solve ill-defined problems, such as how to get that bookcase up the curvy staircase
into your apartment. When someone tells you their IQ score what they're really telling you is their analytical intelligence. The scores are scaled so that
an average person scores 100, so depending on where you
are in relation to 100 you can tell how you compare
to the population at large. You may be wondering how intelligence affects people's lives. Obviously, people with high
analytical intelligence tend to do well in school, however, people who score high on any of the intelligence scales
we've mentioned so far don't really tend to
have better marriages, raise their kids better
or achieve greater mental and physical well-being
than people who score lower. For this reason, another
psychologist proposed that there is another type of intelligence called emotional intelligence. This ability helps you
perceive, understand, manage and use emotions in
your interactions with others. Yet another way of
thinking about intelligence is in terms of two major categories, fluid intelligence and
crystallized intelligence. Fluid intelligence is our ability to reason quickly and abstractly, such as when we're solving
novel logic problems. Crystallized intelligence,
on the other hand, refers to our accumulated
knowledge and verbal skills. The main difference here
is that fluid intelligence tends to decrease as we
move into older adulthood, whereas crystallized
intelligence tends to increase or stay the same. With all this talk about
different definitions of intelligence, you're probably wondering how it ever gets measured. Interestingly, the first person to develop an intelligence test actually didn't even mean for
it to be an intelligence test, Alfred Binet was just trying to establish a child's mental age in order to measure children's
intellectual development and predict how well
they would do in school. Later on, a psychologist
at Stanford University modified Binet's original test and extended it to teenagers and adults. One thing that the Stanford
psychologist noticed was that Binet's original test items, which were originally
designed for French children, didn't seem very predictive of California children's abilities. After he modified the test, unfortunately people forgot
about that difference and started using the new version to judge how generally
intelligent immigrants coming into the US were. Now, you can probably see
the problem with that, even from just a language perspective. If a test is trying to
measure verbal ability, then you might be able to do just fine in your native language,
but it's a lot harder in a language you don't know. Since then, more pains have been taken to try to make intelligence
tests more applicable to people from all different cultures, but it's an ongoing issue. One last consideration that's inherent in any question of traits or talents, but particularly popular
with intelligence, is the question of nature versus nurture, that is, how much is
intelligence due to your genes and how much is due to your environment and other experience? We study this question by
looking at heritability, which is the proportion
of variability in a trait that's due to genes. Specifically, we usually
study heritability with twin and adoption studies, meaning
we look at the corelation between intelligence
scores in identical twins, two people with the exact same genes, who grew up in different environments. We also look at the corelation and scores between identical twins raised together, as well as the corelation and scores between fraternal twins raised together. Since we have a mix of
same and different genes and environment, we
compare those correlations and try to determine what proportion of the variability in those scores we can attribute to genes and what proportion is
attributable to the environment. What we know from these studies is that of those three groups there's the strongest
corelation and IQ scores between identical twins raised together. That alone doesn't really
tell us about any differences between nature and nurture,
though, so let's keep going. Identical twins raised apart still have a high
corelation, but not as high, suggesting some environmental
influence on intelligence. Fraternal twins raised together have an even lower corelation, though, suggesting that there is
also a genetic component. So the short answer is
both nature and nurture contribute to intelligence. Since we tend to have more
control over the nurture aspect than the nature aspect,
there's been a lot of research into what types of environments
promote intelligence, especially for children. Interestingly, although we know some environmental situations that impair normal cognitive functioning, there's no recipe for
structuring an environment to make a genius, when
children are deprived of exposure to language or
interaction with people, their intellectual
development is impaired. However, there's not
a direct relationship, tons and tons of language
exposure helps a child, compared to no exposure, but it doesn't necessarily
make that child a genius. Perhaps even more important
than just intelligence score is your attitude toward intelligence. Some people have what's
called a fixed mindset, they think that intelligence
is biologically set and unchanging, others have
what's called a growth mindset, meaning that they think
intelligence is changeable if you learn more. People with a growth mindset
tend to be more motivated and able to accomplish
more in their careers, than people with a fixed mindset. So, whatever your IQ score is
or isn't, try to keep in mind that you can always grow and always learn.