The two situations, as described in Parts 1 & 2, are identical.
Were your choices consistent? If you chose A in part 1 and A' in part 2, then your choices were consistent. The Part 1 decision and the Part 2 decision are identical, just worded differently.
Most of the human race would choose inconsistently. Don't be surprised if you are among them.
The expected number of survivors in A and A', B and B' is also the same: 200, and the expected number of deaths is 400 in each case.
A and A' have one possible outcome: 200 live and 400 die. B and B' present two probabilistic outcomes: there is some chance that all of them will live, and a larger chance that all of them will die.
If you chose A and A', then, in effect, you chose for 200 people to live and 400 to die, with certainty.
According to Kahneman "Thinking Fast and Slow" , this is an example of the effect of "framing". Presented with Part 1, which presents in the frame of surviving (surviving is "good"), most people will choose A. The same people, then presented with Part 2, which presents in the frame of dying (dying is "bad"), will choose B' and take the long odds of saving everybody. This tendency holds true for public-health officers, MBA students, cab drivers, everybody. (The response also holds true when separate samples of respondents are asked to decide on Parts 1 and 2.)
Kahneman's explanation is that our minds resolve decisions "between gambles and sure things differently, depending on whether the outcomes are good or bad. Decision makers tend to prefer the sure thing over the gamble (they are risk averse) when the outcomes are good. They tend to reject the sure thing and accept the gamble (they are risk seeking) when both outcomes are negative.
This dismays us. How could people who make even the most important decisions be swayed by such a superficial manipulation? But this is how human minds work.
Our best strategy: remain aware of and accept and cope with this human inconsistency.
Looking for Part 2? Click Here.
Looking for Part 1? Click Here.
Daniel Kahneman presented this thought experiment in his book "Thinking, Fast and Slow" http://smile.amazon.com/dp/0374533555
Photo: San Francisco Department of Public Health http://www.sfcdcp.org