My observations here on LW, thanks to the karma system, lead me to believe there is no threshold effect. People always have great difficulty following the ideas of someone a level above them, regardless of what level they are at. Eliezer's posts are so friggin' long because they are designed to be understood by people a level below him.

I suspect, as I've said repeatedly on LW, that increasing the baseline of intelligence would only lead us to construct a more elaborate society, with more complicated problems, and an even greater chance of catastrophic failure. So the question, if you're interested in decreasing existential risk, is whether we can reduce bias without raising the level of intelligence.

A study reported in Science about a month ago indicated that people in Sweden are more able to be laughed at than people of any other nation, while people in Africa and the Middle East are the least-able to stand being laughed at, and the least-trustful of smiling people. I'm intrigued by the idea that simple social conventions may be as effective in avoiding bad social results, as are better reasoning abilities. It may be better to use your reasoning ability to choose good social conventions, and promote those, than to promote rationality.