How many pure Japanese-Americans are there? I would think a whole bunch of them mixed with other Americans by now. They do tend to be highly mixed among the ygunoer cohorts, but I'd assume they tend to marry those of equivalent SES. So their kids are not going to be any less intelligent. Similar to how Jews intermarry, but their kids come out smart becuase they marry smart gentiles. The bigger point is that Japanese are not radically overrepresented the way other Asian groups tend to be.