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The study of human intelligence

edition 70 | interview with Russell Warne

Russell Warne is a psychology researcher with the U.S. Army and formerly a professor of psychology at Utah Valley University.

His book is In The Know: Debunking 35 Myths About Human Intelligence1.

We spoke in May 2024.

Ryan: How would you define little g general intelligence?

Russell: g is a statistical result, identified with a procedure called factor analysis. It is the shared variance across a bunch of different scores.

The scores are sub-tests on an intelligence battery. What does that mean? Why do we care? That shared variance seems to be measuring this general cognitive capacity to do a bunch of different tasks, whether it’s memorize a short list of words and then repeat it later, or solve a visual problem, whatever those different tasks have in common, that’s identified with g.

What’s causing that variance is the common problem solving ability that people use for every one of those tasks. What is that problem solving ability? Well, I call it intelligence.

Ryan: Do you think about creativity as uniquely human? Do you think there’s something like that in other animals?

Russell: I don’t think there’s a global creativity the way that there’s a global intelligence. Creativity is very discipline-bound.

A creative novelist like Stephen King is not creative in physics. The more similar two disciplines are, the more transfer there can be. But if you're talking about idea generation, if you’re talking about innovative ways to problem solve, I think that other animals can find those solutions.

The question then is, can those solutions be culturally transmitted? In some primates and some birds the answer might be yes, or in some species definitely is yes. To be creative is not just solving a problem or creating an original product. It also has to be valued by your community.

That requires a species to be coherent enough and have a common enough culture and communication base that one can say, "Hey, this organism is doing X. That’s good and I can imitate and do X also." If your community doesn’t recognize the value of what you’re doing, then it’s not going to be seen as a contribution that goes above and beyond what they were already doing.

If you’re very generous, yes for some species for some tasks, but I don’t see elephants sitting around and sculpting. Innovative ideas and solutions are a lot more difficult for other species because we’ve evolved a lot of cognitive flexibility that other species haven’t.

Ryan: Cognitive flexibility and complex language perhaps?

Russell: For humans, yes. Not for other animals necessarily. There is cultural transmission without language.

Ryan: Monkey see monkey do?

Russell: Yes actually, literally monkey see monkey do. Different populations of monkeys have different ways of grooming one another, and those seem to be culturally transmitted by literally monkey see monkey do.

And other animals adopt human behaviors. We see that some birds adopt human objects for decorating nests and that will spread among other birds. So we even have some sort of cross-species cultural transmission through objects, but humans seem to be the only ones that do it through language.

Ryan: If you think about your earliest memories, they probably came after language. What is your earliest memory in life, and do you think it is a coincidence of development that we get language and then persistent memory, or is there maybe a connection?

Russell: My earliest memory is being roughly three years old, and playing a game in the church nursery. And it's an image, by the way. I can verbalize and describe it, but I remember it as an image.

Most babies start to understand simple commands and their name at about five to eight months. Then most children speak their first word at about 11 to 13 months.

Most people don't have a memory before three years. I don't know how much of it is just the fact that the lasting memory almost always comes after language, and I don't know if language creates memory.

I'm not sure we can answer it. In humans, language precedes permanent memories by a couple years.

Ryan: Technology is changing our ability to have high resolution information about timing and where stuff is happening in the brain. Is there anything in that field that you’re excited about for the future?

Russell: The leaps and bounds in brain imaging are amazing. I'm really liking this thing that plots white matter.

I think white matter has been understudied compared to gray matter in the brain.

This technology that’s become more widespread in the past 10 or 15 years maps out white matter tracts that connect one area of the brain to another. It’s not my area of expertise, but I still think it’s cool.

Ryan: What can we learn about intelligence from memory experts and savants?

Russell: Savants are really interesting. You can’t always generalize about an unusual organism to the rest of the species. The boundaries between what savants can and can't do is very illuminating and tells us a lot about a typically developing person’s abilities.

Some savants can do really amazing things, but they’re not good at creativity. They're not good at doing new things.

The gentleman that Rain Man was based on passed away several years ago. He lived in Salt Lake City, and I lived in Utah before I recently moved. His name was Kim Peak. He was a local celebrity in Utah.

Mr. Peak had an extraordinary memory. He could memorize a phone book by reading it once. He could tell you the phone number of anyone in the book.

He could tell you what happened on historical dates. He was very good at memorizing, but he never used this knowledge to, for example, write a history of the world.

I'm not criticizing Mr. Peak. But understanding his limitations tells us innovation requires more than just memory; creativity requires more than just just knowledge.

You see this with art savants and music savants. They can imitate a concerto on the piano. They can imitate a drawing. But if you tell them to compose something original, or create an interpretation of some historical event, they can't do it.

Ryan: Your book gets into the effects of pollution on cognitive performance. How bad is lead poisoning for IQ? And should municipal water be supplemented with iodine?

Russell: We know that lead poisoning can lower intelligence, lower IQ. And we know that iodine deficiency does the same thing.

The good news about lead is that, in wealthy countries, the amounts of lead that people have in their bodies is so low that if we were to eliminate it completely, I don't think we would notice the change in IQ.

That was not true 50 years ago. When I was researching that chapter of the book, I was astonished how high some of the lead levels were. And not like, here's a sample of kids living next to a factory that spews out pollutants 24 hours a day.

In the general population, “low” amounts of lead in the 1970s are three or four times the level that today health authorities get concerned about.

Studies would describe children with “low” levels of lead at around 20 micrograms per deciliter. Today we start getting worried when it's five or eight.

Ryan: Those would be people in their seventies now?

Russell: Yeah, people in their fifties, sixties, and early seventies today.

The main source of lead at that time was mostly from leaded gasoline. When I would teach this to my students, they were dumbfounded. Gasoline doesn’t have to have lead in it. It was added to gasoline in the 20s to reduce engine knock and everyone knew it was harmful.

It would send lead out in the air, but they said, “Oh well, it’ll make our cars run slightly quieter.”. The United States got rid of lead in gasoline in the 90s, and other countries followed. That alone has made lead levels plummet. Other things like getting rid of lead paint also helped in the 70s.

Very few people today live in buildings with exposed lead paint, in the United States. If we were to spend the time and money to get rid of lead, I don’t know that there’s much more IQ improvement to do.

With iodine, no, we don't need to add iodine to the water, at least not in the United States. Iodine has been added to table salt for about 100 years, and most Americans get far too much salt in their diet.

There are parts of the world where there's not a lot of iodine in the natural environment, in the water. Central Asia is a good example, parts of Africa, parts of South America. Those places would benefit from iodine supplements, and there are charities where you can donate.

Addressing iodine deficiency to try to prevent mental disability, those are very effective charities. Iodine's cheap. You can iodize a whole package of salt for just a couple pennies. Donating 10 dollars to a charity like that can provide enough iodine tablets to help every child in an entire town and prevent them from having an intellectual disability.

But we don't need that in the U. S..

Ryan: What do you think about the intelligence of American political leaders? What are they uniquely good at?

Russell: I say this as someone who hates both major parties in the United States: the average congressman or senator is uniquely good at exploiting the irrational fears of their colleagues and their constituents.

That’s more Machiavellian than intelligence. It’s common to look at politicians saying something stupid or proposing a bad policy and say, “Oh, what an idiot!”. But I don’t think that there’s a single person in Congress with an IQ lower than 110 or 115.

Same with governors. I would be extraordinarily surprised if you could find one. Because you’ve gotta have a brain in your head, and a pretty good one, to convince thousands of people to vote for you and not for the other guy.

Running a campaign, even if you have a campaign manager, takes some brains. And clearly these people have succeeded in that.

Ryan: Is intelligence research a threat to equality?

Russell: I know a lot of people are concerned about that, but scientific progress is just the matter of uncovering truth. There’s certain types of equality, and I go into this in the book.

There’s moral equality, political equality, equality of outcomes...I fervently believe that, we will be more successful in devising policies that match our social goals if those policies are based on reality and truth and not on incorrect ideas or wishful thinking.

If you want equality of outcomes or some other type of equality, more power to you. Those can be very good social and moral goals. Base them on truth and you’ll be more likely to get there. You can use intelligence research for that. And I give some examples in the book.

Ryan: What research question are you most interested in answering?

Russell: There are a couple. Some of them I don’t have the expertise to be able to answer or even make progress on. I’m relying on colleagues, some much smarter than I am, to find those answers.

As far as ones that I can contribute to, I am extremely interested in, cross-cultural measures of intelligence.

I published an article about five years ago in Psychological Bulletin, where I found archival data from non-western countries, developing nations, and, I did factor analysis. Over 95 percent of the datasets produced a general g factor.

That doesn’t necessarily mean the g we found in Kenya is the same as the g we found in Nepal. But in these countries, which I picked because they were the least likely to have a western style result, because they were economically developing, I still found western-like results, and over 95%.

That tells me that this general cognitive ability is probably universal among humans, and probably in other animals. There is this universal ability, but that does not mean the manifestations are universal.

The way American adults show their intelligence may be very different from the way that children in Zambia do. And that may be very different from the way women in Cambodia show their intelligence.

I'm very interested in finding tasks that work across multiple cultures. So we could explore, is the Cambodian g the same as the American g?

Cross-cultural research is very difficult to do. I wish I had more resources, but I am trying to make progress on that. We'll see.

Ryan: And that might open the door to travel, which would be cool, it sounds like.

Russell: Yeah, it’d be cool to do some traveling. I’ve made progress with archival data, but that’s something that would be interesting for test development.

I have a colleague that wants to work with me in developing a test in his country, so I think we can make some progress.

Ryan: Russell, I appreciate you. Thank you for taking time to talk today. I loved your book. Thank you so much.

Russell: Thanks. Take care.

Russell Warne’s book is In the Know. His website is

Russell Warne
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