How malleable is IQ?

I reproduce below an enthusiastic summary of a famous study which reported considerable malleability in children's IQ score. Following that report I will offer some remarks about it.

In 1969, UCLA psychologist Dr. Robert Rosenthal did an IQ experiment.

He met with two grade-school teachers. He gave them a list of names from their new student body (20% of the class). He said that each person on that list had taken a special test and would emerge as highly intelligent within the next 12 months.

In reality, those students were chosen totally at random. As a group, they were of average intelligence.

The incredible finding is that, when they tested those children near the end of the year, each demonstrated significant increases in their IQ scores.

https://medium.com/mind-cafe/a-lie-transformed-childrens-iqs-why-you-need-radical-self-belief-23f3454d5515

The twin studies always point to a large genetic component in IQ -- as high as 80%. That means that IQ is not very malleable. You are stuck with what you are born with.

This is a highly objectionable conclusion to Leftists in particular, who tend to regard people as a blank slate upon whom can be imposed traits desired in some Leftist idea of a good thing. The "new Soviet man" in early Bolshevik thinking is perhaps the best example of that. So various treatments of children have been proposed with the aim of redirecting their growth.

The most decisive test of our ability to change what children become is undoubtedly the long-running American "Head Start" program. It was designed to take children from disadvantaged backgrounds and enrich their early education in various ways. The experiment did give some early hopes of success but the long term conclusion was that the interventions had no lasting effect. "Enriching" the environment did nothing

But what about that 20% which is NOT genetically given? Could that potential be worked on in some useful way? Did the Head Start experiment simply push on the wrong levers?

All the studies so far have not found much that could profitably be changed. Early nutrition is an obvious candidate for change but even in ideal circumstances only about 5% of the variance could be accounted for that way

An interesting possibilty is that people can be made more intelligent by being treated as more intelligent. That unlikely possibilty is in fact the conclusion of the famous Rosenthal study of experimenter expectations above. There are many problems with the study which I will allude to briefly hereunder but what interested me in the study was how large were the differences found. That is not usually mentioned. They were in fact slight.

The results showed that the favoured students' IQ scores (experimental group) had risen significantly higher than the average students (control group), even though these alleged favoured students were chosen at random. They gained an average of two IQ points in verbal ability, seven points in reasoning and four points in overall IQ.

So the effects observed were slight. The two points in verbal ability were especially notable as the verbal ability score is usually the best predictor in an IQ test. So the Rosenthal treatment showed no substantial success in making IQ more malleable.

Wikipedia gives a useful summary of other problems with the Rosenthal study. I reproduce it below:

"The educational psychologist Robert L. Thorndike described the poor quality of the Pygmalion study. The problem with the study was that the instrument used to assess the children's IQ scores was seriously flawed.[6] The average reasoning IQ score for the children in one regular class was in the mentally disabled range, a highly unlikely outcome in a regular class in a garden variety school. In the end, Thorndike concluded that the Pygmalion findings were worthless. It is more likely that the rise in IQ scores from the mentally disabled range was the result of regression toward the mean, not teacher expectations. Moreover, a meta-analysis conducted by Raudenbush[7] showed that when teachers had gotten to know their students for two weeks, the effect of a prior expectancy induction was reduced to virtually zero".

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