The Paradox of Epistemic Risk


Does your attitude to risk change based on the type of uncertainty you harbour? This is a blog post about epistemic and non-epistemic risk.

Here is a quote from

"Australians [have] an 8.2% chance of being diagnosed with bowel cancer over their lifetime [...] If we assume that a quarter of the Australian population eats 50 grams per day of processed meat, then the lifetime risk for the three-quarters who eat no processed meat would be 7.9% (or about one in 13). For those who eat 50 grams per day, the lifetime risk would be 9.3% (or about one in 11)."

There are at least two ways to interpret the above quote:

Option 1:

  • there is a 9.3% chance of getting bowel cancer for processed meat eaters and a 7.9% chance for non-processed meat eaters; genes don't matter

Option 2:

  • there is a x% chance of having the genes that make you susceptible to bowel cancer
  • if you have the genes that make you susceptible: there is a high chance of getting bowel cancer if you eat meat
  • if you don't have the genes that make you susceptible: it doesn't matter what you do, there is a low chance of getting bowel cancer

In either case, we can assume the marginal probability of getting the illness is the same (i.e., we can adjust the percentages in option 2 to make them the same as option 1). If you're a processed meat eater, look at Option 1 and think to yourself: is never eating bacon or a burger again worth 1.6 percentage points reduction in risk? I'm not sure what my answer is, which means that the choices are fairly balanced for me.

Now look at Option 2. Does your answer change? For a rational agent it should not change. My inner monologue for Option 2 goes as follows: if I have the bad genes, then I'm definitely screwing myself over by eating processed meat, and I want to avoid doing that.

But you don't get to know what genes you have (at least, not yet, that will probably change in the next few years), so the main source of risk is epistemic. That is, you already have the genes that you have (tautological though it is to say), you just don't know which kind you have.

Here's what I think is going on: as we go about our lives we have to "satisfice" which means that we focus on actions that are expected to make big differences and try to avoid fiddling at the margins. Option 1 looks a lot like fiddling at the margins to me. Option 2 instead gives me more control: if I have the bad genes then I'm in much greater control over the risk of a terrible illness. But the greater control is illusionary: as long as I remain uncertain about the state of my genes, the utility of eating or not eating processed meat is the same for both Option 1 and Option 2. I call this the paradox of epistemic risk.