Even if white people are smarter in average than black people, I think just talking with somebody for ten minutes would give me evidence about their intelligence which would nearly completely screen off that from skin colour.
What if verbal ability and quantitative ability are often decoupled?
I wasn't talking about "verbal ability" (which, to the extent that can be found out in ten minutes, correlates more with where someone grew up than with IQ), but about what they say, e.g. their reaction to finding out that I'm a physics student (though for this particular example there are lots of confounding factors), or what kinds of activities they enjoy.
Here's the new thread for posting quotes, with the usual rules: