Our most recent read for the USV book club was the Immortalists by Chloe Benjamin. The book chronicles the lives of siblings who as adolescents were foretold the dates of their deaths. One of the key questions we talked about when discussing the book was whether or not one would to know such information. While the case in the book is intentionally extreme, we face similar decisions when it comes to our health. For instance, some people do not want their DNA sequenced for fear of discovering a dangerous mutation.

What does an understanding of uncertainty have to tell us about these kinds of questions? If you have been following continuations for some time you may recall that I had my DNA sequenced. I firmly fall into the it is better to know more camp. At the highest level, more information means reduced uncertainty. This is almost tautological. If your uncertainty is not reduced, you have not in fact received information.

Earlier in Uncertainty Wednesday, I worked through the example of a PSA test that potentially indicates prostate cancer. Prior to taking the test you have a certain probability of having prostate cancer (assuming you are male), that largely depends on your age. Once you get the test result there is a new probability distribution with reduced uncertainty. Depending on the result of the test you are now more or less likely to have prostate cancer than the average male of your aged.

If you were to ask most people if they prefer more or less uncertainty, they will say less. But that includes the people who would rather not sequence their DNA or get the results of their PSA test. So what that subset of people is really saying is that they don’t want to receive bad news. They prefer more uncertainty over less, when the information they would receive might point to a bad outcome.

This of course brings us right back to my prior post about Fear and Acceptance. Not wanting to know is quite likely driven by fear. But today I want to take it into a different direction. What should you do once you receive information that increases the possibility of a bad outcome?

Well, one of the key things about living in a world of pervasive uncertainty is that you should not immediately assume the worst. You should be careful not to overreact. That was the whole point of the many prior posts about Bayesian updating. Most information is quite noisy itself and so the adjustment you should make in your believes needs to reflect that.

Strangely we are now finding ourselves is that doctors are telling people not to have a PSA test (I was literally told this at my last physical) because there has been so much overreaction to test results. People immediately went into aggressive treatment instead of maybe just repeating the test. That over reaction led to a lot of bad outcomes, which then in turn resulted in doctors recommending against doing the test.

Instead of not knowing or overreacting, the key is to use the new information to help you make better decisions. Often that starts with simply verifying the information or using it as the impetus to gather even more information.

Now I am curious to hear from readers what kind of information they would like to know or not know and why. I will then write about some of these in upcoming posts. So please let me know in the comments!