I basically agree that having intuitions similar to those I outlined seems very important and perhaps necessary for getting involved with EA. (I think you can be “interested” without those things, because EA seems shiny and impressive if you read certain things about it, but not having a sense for how you should act based on EA ideas will limit how involved you actually get.) Your explanation about exposure to related concepts almost definitely explains some of the variance you’ve spotted.
I spend a lot of my EA-centric conversations trying to frame things to people in a non-quantitative way (at least if they aren’t especially quantitative themselves).
I’m a huge fan of people doing “basic groundwork” to maximize the efficacy of EA messages. I’d be likely to fund such work if it existed and I thought the quality was reasonably high. However, I’m not aware of many active projects in this domain; ClearerThinking.org and normal marketing by GiveWell et al. are all that come to mind, plus things like big charitable matches that raise awareness of EA charities as a side effect.
Oh, and then there’s this contest, which I’m very excited about and would gladly sponsor more test subjects for if possible. Thanks for reminding me that I should write to Eric Schwitzgebel about this.