I'm curious about this one. Personally, I am not persuaded by Reinin dichotomies, but this one piques my interest. The Wikisocion describes it similarly to "optimist" and "pessimist" but based on what I know about twin research, optimism and pessimism are very much learned behaviors. Does positivist and negativist mean something more complicated? Or does it simply describe what we are naturally inclined to fall into, with lack of external stimuli?