A framing effect is demonstrated by constructing two transparently equivalent versions of a given problem, which nevertheless yield predictably different choices. The standard example of a framing problem, which was developed quite early, is the 'lives saved, lives lost' question, which offers a choice between two public-health programs proposed to deal with an epidemic that is threatening 600 lives: one program will save 200 lives, the other has a 1/3 chance of saving all 600 lives and a 2/3 chance of saving none. In this version, people prefer the program that will save 200 lives for sure. In the second version, one program will result in 400 deaths, the other has a 2/3 chance of 600 deaths and a 1/3 chance of no deaths. In this formulation most people prefer the gamble. If the same respondents are given the two problems on separate occasions, many give incompatible responses. When confronted with their inconsistency, people are quite embarrassed. They are also quite helpless to resolve the inconsistency, because there are no moral intuitions to guide a choice between different sizes of a surviving population.

"Such irrational reversal in choice preference, however, was eliminated when the same life-death problem was described in a more ecologically valid small-group (6 or 60 people) or family context. That is, the outcome-framing effect disappeared when the sizes of the hypothetical patient groups were in the range of those that would have characterized hunter-gatherer groups."