I'm going to do my own search when I get to a computer, but thought I'd ask here as I know there are people doing research etc., who might know where the good stuff is. I don't think I can be too much more specific than what I said, as I really just want to explore the area. Like the EQ, for example, I'd be interested to see if there are any Rational Thinking Quotients or similar. Could be any aspect of rationality that could be measured - a broad look at the concept, or something specific like rational decision-making or rational belief generation, anything really. The important thing is that the articles etc. are about measurement, so a survey or something.
I know there are many ideas about what makes someone a rational thinker, so I expect it's a somewhat controversial or debate-laden area of research. I'd love to explore it.