I am starting to dip my toes into the Richwine thing. I haven't read his dissertation or the Heritage paper yet. I really despise the big picture: closing the door to the United States because we find immigrants undesirable in some way, etc. Talking about the IQ differentials of different groups just makes me queasy too.
But I'm also concerned about how some people are going into this and making their arguments against Richwine.
Intelligence is a real thing, OK? It does vary across the population. I defer to the psychologists on what to think of any particular metric (paging my own favorite psychologist on this one - commenter Dr. J). But it's a real thing. It's not the only thing we ought to care about, of course, which is why I don't like making policy on the basis of a few qualities we find to be desirable. But it's a real thing.
One thing the IQ of an immigrant population relative to the native population is going to depend on is selection effects: is there negative or positive migrant selection? This is dictated by a lot of things including geopolitics and the specific immigration statutes - but it's also dictated by the comparative advantages of potential migrants.
Let's say Latinos in Central and South America have precisely the same IQ distribution as native Americans. Exactly the same. If there is negative migrant selection, Latino immigrants to the United States will have a lower IQ than natives. There's nothing racist or controversial about it - that's math. The U.S. average IQ will go down and the Central and South American average IQ will go up (because relatively lower IQ residents will migrate to the United States).
If IQ is highly determined by genetics (I defer to the geneticists on this) and marriage is highly determined by ethnic and immigration status (I defer to the sociologists on this), the differences will persist.
If IQ is highly determined by child nutrition (I defer to the child development people on this) and Latino immigrants remain relatively low income, the differences will persist.
This is just a fact of life people.
Now what bothers me about Richwine is I can't imagine what motivates a person to get into these questions. Maybe Latino immigrants are lower IQ. That is entirely plausible to me.
But I really don't care about that and that doesn't really register on my list of things that ought to guide immigration policy.
I guess some people do, but I am suspicious of people who have a deep interest in comparing the IQs of different populations.