Worth noting in this discussion: Einstein never took an IQ test, at least none that historians know of. Pretty much any time I see a claim about a historical figure's IQ, it turns out to be an invented figure made on the basis of a totally unscientific "estimate." The tendency of pop writers about intelligence to use these invented historical IQs as a measuring stick makes me doubt the whole enterprise (though I'm not singling out Gladwell here, whose books I generally like).