C.f. the cited book by Hart & Risley, Meaningful Differences In The Everyday Experiences of Young American Children.
"The more parents talked to their children, the faster the children's vocabularies were growing and the higher children's IQ test scores at age 3 and later. [...] [By age 4], an average child in a professional family would have the accumulated experience with almost 45 million words, an average child in a working-class family would have accumulated experience with 26 million words, and an average child in a welfare family would have accumulated experience with 13 million words. [...] Just to provide an average welfare child with an amount of weekly language experience equal to that of an average working-class child would require 41 hours per week of out-of-home experience as rich in words addressed to the child as that in an average professional home. [...] By the time children are 4 years old, intervention programs come too late and can provide too little experience to make up for the past."
The basic idea is that the best determiner of academic success is the number of words per day spoken to the child (listening to audio/tv doesn't work, and is generally thought to be harmful, especially before age 3.) Essentially by the time kids get to kindergarten, there is already a 2+ year achievement gap between wealthy kids and poor kids, mostly for this reason. In addition to being enormous on its own, this gap then compounds greatly because of tracking, which tends to be introduced in some form or another starting around age six:
"We found that first-grade ability-group placement can have persistent effects on children's achievement in school over a period of several years and may shape the expectations of children's performance held by significant others, such as parents and teachers. Whether these effects are instructional, social, or institutional, they are real, and they have implications for children's future schooling trajectories. [...] Instructional grouping may have the unintended effect of increasing inequalities in educational outcomes, largely by creating inequalities in educational resources and rewards." (I forget the author, but this is quoting in Riordan's book Equality and Achievement in the relevant section.)
Anyway I'd definitely recommend reading Meaningful Differences, in addition to being a great example of how science should be done in terms of robust methodology, it's also one of the most insightful and important scientific findings of the last hundred years.
The one thing I'd add though is that in addition to the total volume of language, which is the most important variable, there are a few other counterintuitive findings worth knowing about. E.g. reading aloud to your kids doesn't actually benefit their language skills, unless you purposely use certain linguistic constructs while reading to them. And there are other linguistic features you can use that are beneficial, that you wouldn't necessarily think to use without knowing the research, but I'll stop there though so as not to spoil it.
How did the researchers determine causation? What if there is simply a gene for strong language which is responsible both for the parents' financial success and the child's academic success, and the extra words were simply a by product?
> How did the researchers determine causation? What if there is simply a gene for strong language which is responsible both for the parents' financial success and the child's academic success, and the extra words were simply a by product?
Yes, it might well be the classic confusion of cause and effect, but your argument will have no effect on the OP, who is a psychologist.
For reasons that may or may not be obvious, as part of their training, psychologists are made blind to the possibility that they might confuse cause and effect.
Sure, just read their professional literature -- it's a treasure trove of examples that confuse cause and effect. To a degree greater than any other field with scientific pretensions, psychologists ignore the possibility that they're reporting something that either has no objective reality, or is a case of correlation mining.
Quote: "In their exhaustive final report about the fraud affair that rocked social psychology last year, three investigative panels today collectively find fault with the field itself. They paint an image of a "sloppy" research culture in which some scientists don't understand the essentials of statistics, journal-selected article reviewers encourage researchers to leave unwelcome data out of their papers, and even the most prestigious journals print results that are obviously too good to be true."
lutusp has strong anti-psychology sentiments. Conversations about it tend to be, uh, unproductive.
EDIT: It's a shame, because a lot of what he says about psychology and the flaws in the science is useful and interesting. Psychology has a lousy history of weak science. And any modern researcher could be making mistakes while striving for good science. So it's nice to hear from someone who does understand the importance of rigour.
> lutusp has strong anti-psychology sentiments. Conversations about it tend to be, uh, unproductive.
You know, you could address the topic, not the participants. To fail at this is the very definition of counterproductive.
> Psychology has a lousy history of weak science.
Yep. People have asked me why I focus on psychology, since all fields have embarrassing episodes in which the principles of science are ignored. The answer is that, although psychologists have clinics, they don't have enough science to justify their existence.
Sociologists are equally unscientific, but they don't have clinics.
Doctors also have clinics, but they're much more scientific.
This makes psychology a conspicuous gap in the system meant to protect the public from charlatans. But the gap is closing -- the director of the NIMH, the highest-ranking psychiatrist in the country, recently decided to pull the plug on the DSM and, by implication, psychiatry and psychology.
Quote: "While DSM has been described as a “Bible” for the field, it is, at best, a dictionary, creating a set of labels and defining each. The strength of each of the editions of DSM has been “reliability” – each edition has ensured that clinicians use the same terms in the same ways. The weakness is its lack of validity."
Show me that the majority of psychology (and sociology) papers published in reputable journals are unscientific, then publish that in a reputable journal (then just post the link to that article as a response to this comment). As that is what you are claiming. Anything less and you are being hypocritical.
You are making a very big claim, so go and do the work to back it up.
The studies cited in the Slate article come out of education and speech-disorders research. Those fields have problems too, but not all of the same ones as clinical psych.
The studies seem to be confusing causation and correlation. They seem to assuming that there must be an environmental cause for the differences in people's IQs. This may seem like a stupid assumption to make, but a lot of people in the social sciences take this as a given, even though the weight of evidence is strongly against it.
Perhaps I have missed something, but I would expect that, if they did not have ideological blinkers on they would be saying things like:
"We are taking particular care to separate environmental and genetic factors here by including adopted children, [identical] twins reared separately, other children raised by other than biological relatives".
But I see none of this at all here.
You may be interested to read "The Nurture Assumption" for a detailed analysis of the effect of parents on their children. The basic conclusion is that if you do not seriously abuse your children you don't affect them much one way or the other. Steve Pinker's book "The Blank Slate" is also relevant.
Today everyone can and usually does criticize "cause vs effect" whenever a study doesn't fit into his world view.
The discussion usually is omitted in journalistic articles anyway, so it's easy to say for readers that the scientists just "have no clue".
For me it looks like this research is looking for interventions. They are not just trying to understand intellectual development, but what can be done to improve early education. They succeeded at that. They didn't succeed at satisfying romantic and simplistic understandings about a genetic basis for intelligence.
This is the gold-standard for testing genetic association, yes, but it is increasingly considered unethical. And is not perfect - twins are still likely to be placed in similar homes (typically both in foster homes, after all), which likely results in an overestimate of the genetic effect.
Modern statistics is about handling the data that is available: present-day researchers cannot rely on a statistically perfect study which would have to be generational and eugenic in scope.
That's interesting, but I think there are also studies that show childhood IQ tests don't correlate very well to adolescent or adult IQ tests - which, as others studies have shown, are tests that do correlate well to success/happiness/etc. over lifetimes.
This study would be a lot more interesting if it followed its sample into adulthood and compared IQ scores over time - it very well may do that, it's just not clear from the article that there is very much meaning here when put into context with other studies on childhood IQ.
Childhood IQ tests get complicated by the fact that a lot of what you measure is which children hit growth spurts already, which come with attendant intellectual improvements.
But I have had a psychologist who specialized in the field say that the best predictor of adult IQ was receptive vocabulary. Meaning how many words does the child understand? Understanding words, even words you don't know how to use, predicts future intellectual development because it says who has the foundation.
Adult vocabulary is a strong predictor of adult IQ just as child vocabulary is, but I wouldn't recommend studying vocabulary to get smarter. Being "a predictor" says nothing about being a cause; smarter kids know more words because they're smarter, but the "predictor" relationship is established at the point of "smarter kids know more words".
I am informed (by a Chinese teenager, so possibly not perfectly reliably) that vocabulary size isn't considered a concept in China -- there are words that everyone is expected to know, technical vocabulary, and words that no one is expected to know (by way of example, I use the word "vacillate" in my day-to-day casual speech, but that's unusual, and many native english speakers don't know what it means. That situation is not supposed to be possible in China).
For purposes of my point, the truth of the assertion isn't really relevant. Such circumstances, obviously, mean that vocabulary can't be a predictor of IQ after the age at which it's all been learned. Do you imagine that IQ differences would disappear along with the predictive value of vocabulary size?
You missed the point. The psychologist had specialized in child development. His claim was that receptive vocabulary in grade school children was the single best predictor that was known for their IQ and tests scores in high school and presumably beyond.
Studying vocabulary as an adult is probably not going to get you very far. But having been exposed to a lot of vocabulary when you're young seems to be a good thing.
(He was telling this at the same time that he was telling me that my 7 year old son had the receptive vocabulary of an average 13 year old. So I was happy to hear it.)
> His claim was that receptive vocabulary in grade school children was the single best predictor that was known for their IQ and tests scores in high school and presumably beyond.
This isn't true. For example, IQ as a 20 year old is a better predictor of IQ in high school than receptive vocabulary in grade school is. It happens that it's hard to observe the IQ at age 20 of a child who isn't 20 yet, but that doesn't change the strength of the predictor.
> But having been exposed to a lot of vocabulary when you're young seems to be a good thing.
You provide no support for this other than the fact that a large vocabulary at a young age is indicative of a high IQ later. However, a large vocabulary later is also indicative of a high IQ later. Applying the same logic, you should conclude that being exposed to a lot of vocabulary when you're old is just as good (if not better!).
If you don't think studying vocabulary as an adult will get you very far, why do you think studying it as a child is different?
This isn't true. For example, IQ as a 20 year old is a better predictor of IQ in high school than receptive vocabulary in grade school is. It happens that it's hard to observe the IQ at age 20 of a child who isn't 20 yet, but that doesn't change the strength of the predictor.
A predictor is something that you can measure and make predictions from in advance. Therefore by definition the eventual IQ at age 20 is not a predictor of future IQ for grade school children.
Now can we dispense with the semantic games?
> But having been exposed to a lot of vocabulary when you're young seems to be a good thing.
You provide no support for this other than the fact that a large vocabulary at a young age is indicative of a high IQ later. However, a large vocabulary later is also indicative of a high IQ later. Applying the same logic, you should conclude that being exposed to a lot of vocabulary when you're old is just as good (if not better!).
Not indicative, predictive.
Receptive vocabulary is part of IQ. So of course having a large receptive vocabulary helps your IQ. But children with a large receptive vocabulary when young tend to have future increases in other mental abilities. By contrast children who show high abilities in other areas when young do not show the same improvement.
The theory that I was told is that children who can understand complex verbal things find it easier to learn from our education system. And children can't learn to use complex language without first understanding it.
If you don't think studying vocabulary as an adult will get you very far, why do you think studying it as a child is different?
The research on development that I've encountered indicate that there are specific developmental periods where we are particularly receptive, and where our abilities tend to increase suddenly. Starting with a large receptive vocabulary seems to position you well to make the most of these.
When you're older, studying vocabulary is unlikely to be bad for you. But you don't have the same developmental spurts ahead to try to maximize. Furthermore vocabulary is less likely to be a barrier for adults than children.
For example my son right now loves ants. He is learning things about ants that other children his age would have trouble with because he understands words they don't. But he doesn't have a better vocabulary than most adults. Any literate adult who wants to learn what he is learning about ants can simply pick up material on ants and read it.
The study was primarily looking at language acquisition, not IQ. The researchers themselves did find that language mediated IQ somewhat, but IIRC the effects weren't especially noteworthy. I haven't read the book in a while though, so I can't remember the exact details.
My nephew started speaking early and quite well. He can name and knows lot of things, tens or hundreds of different animals, what he does, wants etc. Some other kids I've seen don't talk at all or they don't know any words.
It seems to me it's because my sister and his husband talk with him all the time, and explain when they're doing something together. I've been trying to do the same and talk normally with him and not talk down to him or some kid nonsense. He talks back and says if he doesn't understand.
"The more parents talked to their children, the faster the children's vocabularies were growing and the higher children's IQ test scores at age 3 and later. [...] [By age 4], an average child in a professional family would have the accumulated experience with almost 45 million words, an average child in a working-class family would have accumulated experience with 26 million words, and an average child in a welfare family would have accumulated experience with 13 million words. [...] Just to provide an average welfare child with an amount of weekly language experience equal to that of an average working-class child would require 41 hours per week of out-of-home experience as rich in words addressed to the child as that in an average professional home. [...] By the time children are 4 years old, intervention programs come too late and can provide too little experience to make up for the past."
The basic idea is that the best determiner of academic success is the number of words per day spoken to the child (listening to audio/tv doesn't work, and is generally thought to be harmful, especially before age 3.) Essentially by the time kids get to kindergarten, there is already a 2+ year achievement gap between wealthy kids and poor kids, mostly for this reason. In addition to being enormous on its own, this gap then compounds greatly because of tracking, which tends to be introduced in some form or another starting around age six:
"We found that first-grade ability-group placement can have persistent effects on children's achievement in school over a period of several years and may shape the expectations of children's performance held by significant others, such as parents and teachers. Whether these effects are instructional, social, or institutional, they are real, and they have implications for children's future schooling trajectories. [...] Instructional grouping may have the unintended effect of increasing inequalities in educational outcomes, largely by creating inequalities in educational resources and rewards." (I forget the author, but this is quoting in Riordan's book Equality and Achievement in the relevant section.)
Anyway I'd definitely recommend reading Meaningful Differences, in addition to being a great example of how science should be done in terms of robust methodology, it's also one of the most insightful and important scientific findings of the last hundred years.
The one thing I'd add though is that in addition to the total volume of language, which is the most important variable, there are a few other counterintuitive findings worth knowing about. E.g. reading aloud to your kids doesn't actually benefit their language skills, unless you purposely use certain linguistic constructs while reading to them. And there are other linguistic features you can use that are beneficial, that you wouldn't necessarily think to use without knowing the research, but I'll stop there though so as not to spoil it.