So, it turns out that the human brain will actively prevent itself from storing information about negative future events.
From the article:


The only people who don't have this "glitch" are those who are clinically depressed. Hmmm, I wonder what that says about ETS members?
This also explains why it is so hard to convince non-believers to prepare. Their brains are blocking acknowledgement that bad stuff could happen.

I explain the original Nature article below. Most of the paper revolved around the statistical analysis of their results. This was done to show why they believe what the test results mean. Their statistical analysis appears sound which strongly supports their interpetation of the results.

What they found (simplified for laymen): the learning centers of the human brain will readily and actively "update" their world-view if their world-view is shown to be less optimistic than reality. However, when the brain's world-view is revealed to be more optimistic than reality, the brain shows a much lower willingness to update its world-view to the less positive view.

How they measured this (again, simplified): It was more than just asking the subjects "how likely is this event?" several months apart. The researchers tracked the Brain Oxygen Level-Dependence (BOLD) during these tests. BOLD is an MRI technique which basically shows what parts of the brain are processing data. As expected, the areas that became active during these tests were the areas generally considered to be the problem solving and memory sections, though they tracked BOLD for the full brain.

Results: When the actual "probability of threat" values were revealed to the subjects their brains responded in one of two ways:
1. If the subject had over-estimated the threat, their brain lit up with activity as it processed this information, with areas associated with analysis and memory becoming highly active.
2. If the subject had under-estimated the threat, their brains showed a much smaller increase in activitely across the board but especially in the memory-storage areas.

This reduced brain activity when assimilating negative information occured in 100% of the test subjects. However, the level of reduction was able to be directly correlated with the subject's overall level of optimism. Those subjects which had the most optimistic view of life had the lowest brain responses to negative information. The two subjects which were clinically depressed had the least amount of difference in brain activity between processing positive and negative information.

Overall, the paper does a really good job of proving (to me, at least) that the human brain does actually ignore negative information. This explains why it's so hard to convince people they should be prepared. Their brains actively suppress the true likelyhood of something bad happening.