Genetics and Intelligence Robert Plomin

one of the areas of research I study is genetics and intelligence and it's one of the oldest studied questions in behavioral genetics going back to the late 1800s with Francis Galton here in England he was the cousin of Darwin for example the gentleman scholar did his research in his home and that sort of thing but he did some of the first work on intelligence and he did it very badly he studied he just studied reputation people who were thought to be very intelligent but what happened in the early nineteen hundreds of people developed measures of intelligence and even now that's contentious for some people but I think it's very well measured and it began with spearmint Charles Spearman in England in 1904 where he said intelligence just means too many different things to different people I mean what do you mean by intelligence really so he said I'm going to define it precisely g-general cognitive ability and what that is is what diverse tests of cognitive ability have in common so you've got hundreds of tests of cognitive abilities like different types of memory different types of verbal vocabulary fluency spatial ability there's many different types of cognitive tests but they all correlate substantially which is quite surprising to people you know you'd be good in verbal means on average you're probably pretty good in memory pretty good and spatial people's own on good at spatial I'm not good at verbal or vice-versa but they are pretty good they just mean they're better at this than that they correlate substantially so that 40% of the variance the individual differences of all those tests are in common and that's what we mean by gee the overlap the covariance among all these tests so it isn't a thing it's what these tests have in common so intelligence tests they're usually the major ones use around the world have about ten different tests they're different some are verbal some are non-verbal tests they're diverse tests and what you do is you put them together to get a score that people usually call an IQ score so it's a pretty good measure of general cognitive ability so general cognitive ability is important because it's the best predictor of society important things like educational outcome and occupational status by far than anything else we have there also among the most heritable tests and neuroscientists are becoming very interested in intelligence as well because it's how the brain works it's how the brain functions and it doesn't function in the way most neurocognitive new respect of psychologists think as little modules in the brain that light up when you do functional MRI the brain works it evolved as a general problem-solving tool and so it uses everything it's got to solve a problem so some of the tests that we celos most highly on G that is they correlate most with this concept of G are like abstract reasoning problem-solving in novel situations and I think people just see that you know if they just say well what do you think is intelligent why do you think they're intelligence it probably has to do with stuff like this it's not just how good you are on these quiz shows like here in England Col University Challenge where you just memorize a lot of facts that isn't really what we mean much by intelligence although to be good at that you have to be fairly intelligent so I mentioned this I emphasize the 6mp of the Oh intelligence what is that well it's one of the best measured things we have - one of the most important predictors we have so it's an important trait it's basically learn ability and say in terms of Education which I particularly say it's some kids learn more easily than other kids every any teacher will tell you that but instead of assuming it's all environmental we got to ask is it genetic and behavioral genetics over the century has shown that individual differences and intelligence are heritable if you take the world's literature of several hundred studies twin adoption family studies you come up with an estimate about 50% but what's really interesting underneath that is if you ask about development it turns out there's a linear increase in the heritability of intelligence from infancy to childhood to adolescence to adulthood infancy 20% childhood adolescence 40% adulthood 60% later in life 80% you first explain what heritability is that's the extent to which differences are due to genetic differences you ask them okay would heritability increase or decrease people will say it decreases why because Shakespeare's slings and arrows of outrageous fortune environmental differences accidents illnesses they all pile up which means that increasingly as you go through life the differences you see ought to be due to the environment but instead it's very much the other direction this has been replicated in many studies you know it's a really solid finding that in heritability of intelligence increases and so if you ask why you know why does this happen and it's what I was talking about before that the way genes work is they're not pro we don't program intelligence test scores in our DNA it allows you to learn more easily and you can learn more difficult subjects and then you choose environments that fit that you know you like to learn difficult things so you read different difficult things you argue with people you know you talk to people who want to discuss intellectual issues and so you create environments correlated with your genetic propensities so that the little differences early in life accounting for 20% of the variance and empathy snowball they increase as you go through life selecting and creating environments correlated with your genetic propensities so that's why I think the heritability of intelligence increases throughout life and I'm particularly interested in applying applying these techniques to education psychology about 23 years ago they didn't accept genetics at all and now it's very dumb everyone accepts genetics education however is this backwater where they don't accept science by and large you know you spend as much money on education as we do on the National Health Service the National Health Service now if you have a new idea a new program you've got to show empirically that it works you have to do randomized control trials in education people just use their hunches and you see so many examples of this I think they're going to have to deal with evidence and prove empirically scientifically that their programs work and then I think they will take genetics seriously right now they just say oh well that's just research and science you know that that doesn't have anything to do with education and it's bizarre because we find that cognitive traits and educational achievement are among the most heritable traits you know kids in England are the most tested kids in the world they have these national curricula and national tests that they take you know different stages in education we find in the first year of school literacy numeracy the things we teach in school are about 65% heritable the differences among kids even as they go into school are very substantially due to genetic differences the heritability of intelligence goes up so in the first few years of school the heritability of school achievement these test scores is higher than the heritability of intelligence then as the inheritability of intelligence goes up it becomes about on a par with the heritability of educational achievement there's a lot of interesting things that we find educational achievement is just as heritable for we call it STEM subjects science technology engineering math as it is for humanities for example so we also find that a lot of the genetic influence overlaps that is it's not just separate genes for learning math and separate genes for learning English it's largely the same genes and substantially that's what we call intelligence it's the same genes that affect all these different aspects of educational achievement when we talk about intelligence it's important to recognize that we're looking at individual differences why people differ on intelligence or educational achievement that's not to be confused with questions about why are humans more intelligent than other species or are we as an average more intelligent than people were before however there's quite a bit of interest in the issue of intelligence increasing that's called the Flynn effect he first noticed this it's been quite a big increase in intelligence over the last at least few decades it seems to have tapered off nobody knows exactly what that's about is it that we're becoming more sophisticated about test taking is it the way we standardize these tests so it's not really clear but what's important to recognize is that the causes of average differences like average differences between us and people 50 years ago or between sexes or ethnic groups have no necessary relationship to the causes of individual differences so a good example is the obesity epidemic we're not only getting may be more intelligent we're definitely getting fatter as all around the world in developed countries that's got to be environmental it's too quick to be genetic but the heritability of weight is just as great across the years across the decades so the causes of individual differences you might be surprised to know most people are we we've done surveys of this we have how heritable do you think height is people say really a heritable like 90% heritable meaning most of the differences are due to genetics weight not very much I mean 30% 40% maybe people say it's 60 70% most of the differences between us and weight are due to our inherited DNA differences even though we've been gaining weight over the decades the heritability has stayed high because the causes of individual differences aren't necessarily related to the average differences and a good possibility is we live we have a Stone Age brain that wants fat that is good if you're going to don't know when your next meal is but if you're in a fast food nation where you're bombarded by food cues all the time it's harder to resist that and so people who have a genetic propensity towards weight are going to put on that weight it's interesting to think about this on the environmental side hoes we're not talking about the average now we're talking about heritability that genetics accounts for a lot of the differences we see in intelligence so what if you were able to make a more equal society what that means is you get rid of the environmental differences you stop privileged you know parents passing on their wealth to their kids for example and giving them educational opportunities that other kids don't have if you can get rid of the environmental differences you don't get rid of the genetic differences so that the heritability increases with equal environments and that means that actually heritability is an index of social mobility of equality what's important about heritability which is the extent to which genetic influences explain behavioral differences we call it observe phenotypic differences I'm we're talking about in a particular population at a particular time with a particular mix of genetic and environmental factors we're describing what is what exists not what could be but now suppose those conditions change as they could change over time in a population or between different populations so say in a Mad Max apocalyptic world were be you know the environments are completely different how will that change heritability it certainly could change it it could actually make it greater because the genetic differences are more important I mean they're life or death issues that you solve all these new problems that you're confronted with you can't just coast on automatic pilot the way we can in our you know relatively civilized world where we know what's going to happen we're not too often surprised but so it's hard to know in the future and in terms of possible environments what would happen but what we do know is if you equate the differences in environments you actually increase heritability and I think that's a really interesting notion in terms equality of opportunity and suggesting that heritability is an index of equal environments

Channel: Serious Science

Views: 139,452

Rating: 4.8637705 out of 5

Keywords: science, lecture, Serious Science, genetics, intelligence, psychology, IQ, IQ test

Id: lev8dGnxvdw

Length: 13min 15sec (795 seconds)

Published: Sun Aug 27 2017

Reddit Comments

[u/IWBN]

A good starting question worth considering: Why do some kids learn stuff easily and fast, while others struggle to make sense of new concept? Is it entirely environmental? no. It's genetically predisposed, too. As Robert suggests, ,,Heritability increases from childhood to adolescence: infancy - 20%; childhood adolescence - 40%; adulthood - 60%; later in life - 80%''.

[u/IWBN]

Maybe we are too quick to say that genes play only minor role determining human intelligence. Geneticist Robert Plomin makes a good case in defense of this claim.

[u/InquiringIntrovert]

Very informative video, and worth posting in light of this recent email debacle. I believe many of us have fallen victim to overreactions and side-taking far too early in the game without many of us realizing or admitting that we haven't actually been well informed on this topic. From videos like this, it's clear that the scientific data is widely accepted and well investigated. Yet, none of this data is published to society at large for us to be able to fairly judge the legitimacy of either Sam or Ezra's statements on the topic.

But how strange is that? Intelligence, of all things, is entirely out of bounds with what science is allowed to broadcast to the rest of us as.. science. The reasons are obvious and don't need to be stated, but intelligence is clearly a form of 'forbidden knowledge'.

I just don't understand how anyone could believe heritability plays no role in intelligence, and then claim it does in mostly everything else. It's actually quite understood and stated in real life dialogue, it just seems taboo to further articulate it.

When listening to a highly intelligent person speak, when have you ever thought to yourself 'what an impressive reflection of the incredible environment that gifted him his mental capacities. His superior environmental factors throughout his life propelled him into this level of thinking." If this was the case, we'd be further studying and debating the perfect environments for maximizing intelligence, as it would play such an absurdly high role in advancing society. And yet how many times have you seen someone who clearly just couldn't grasp the same logic, no matter how much information or help they had from their environment.

You grow up knowing who the smart children are in your class, and you don't credit the environment for their giftedness or blame the environment for non giftedness. America simply tests all of the children and places the gifted children in the same classes as they move past elementary school. The same educational environment for hundreds of children only results in a fraction of 'giftedness'. Was that just gifted parenting? Any denial of heritability appears completely incoherent to me. I'm open to hearing opposing arguments or if I've completely missed the point.

[u/creekwise]

Another of his videos that's related: https://www.youtube.com/watch?v=BYGUjIlq5yA

[u/[deleted]]

Why is he saying literally exactly the same words as Murray in the beginning? Freaky

[u/Tylanner]

Race has been used as a natural dividing line for countless unscrupulous programs. While often perfectly aligned with the selfish gene of our human nature, these are something we ought to do without.

Aligning with Darwin...genes are where you start...how far you go is based on your personal ability to adapt.

To present anything less than irrefutable physical evidence that the specific biological make up of an individual person or people is objectively worse than another individual person or people is utterly irresponsible and only roams the foul plane between loose generalization and gross ignorance.

The notion that IQ is anything more than a subjective metric of the degree to which someones mental faculties are preferenced favorably by the modern industrial world is disingenuous.

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Sam Harris Drops the Red Pill on IQ	+12 - Now, consider this: quote from this video: ,,Whatever the average IQ is across groups, you know nothing about a person's intelligence on the basis of his or her skin color. That is just a fact... So besides being unethical and politically imprud...
DNA and Behavioral Genetics - Robert Plomin	+4 - Another of his videos that's related:
Genetics and Intelligence Robert Plomin	+1 - Listen to what he says at 09:18 though - this is the major problem with the inferences Murray makes, based on these conclusions

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[u/omgpop]

IQ is a very poor predictor of societal outcomes. Parental income is better.