Thank you for this formal (and fun!) method to guide (and illustrate/document) decision-making. I think writing it out would help me illustrate leaps or assumptions and come to better decisions. For instance, I often (in my head) zero-out possibilities that have extremely low probabilities out of hand unless the costs are a similar order of magnitude.
What if the model is giving you an answer you don’t like? Well, it means your “system 1” and “system 2″ are in conflict! The very first question I asked was which way of making decisions you want to use in this case, and the answer was “system 2”, so you should go back and verify all your assumptions; maybe you forgot to consider some events.
How do you avoid rationalizing (introducing bias in) your decision if you’re heavily scrutinizing the tree only when your system 1 and system 2 disagree?
In defining A and B as equally valuable, I have to equate the two. That said, it’s hard to imagine something that exists that would be as valuable to a non-starving healthy child right now as the meal to the starving child, so if the valuable thing you gave in scenario b were at all marketable, the inefficiency of choosing to use it to help b instead of the x (where x > 1) starving children would make the real psuedo-equation:
utility(a) = utility(b)
cost(a) = x * cost(b)
if x > 1, do a, if x < 1 do b