I'm a statistician and I think that MULTICOLLINEARITY is an example of what Tom was looking for. It's not something that is against the grain of understanding but I think it's something that hardly anyone is science or research is acutely aware of but is really quite fundamental to the idea of correlation vs. causation. At the same time with a handful of charts, a child could understand why it's something that people should know about. It really should be more well known and more widely understood.,(reply>), If a child could understand it, why is the Wikipedia page all specialized jargon?