It's been a while, and to get back into the swing of things, I'm actually going to do a post that's not about empathy at all. Gasp. But it is about psychology, and not entirely tangential to the purposes of this blog.
It's about the "Garcia effect." Although that term can actually be used more broadly, I'm using it in the sense of conditioned taste aversion. It turns out that our sense of taste is particularly good at making us associate stimuli and negative responses.
You've all heard of Pavlov's dogs, one of the earliest studies in "classical conditioning." Normally it takes many trials for dogs to associate the sound of a bell with the arrival of food. But for animals, and even humans, the onset of nausea symptoms causes one to quickly associate the sickness with whatever novel taste stimulus we can easily recall.
That is, if you try sushi for the first time, and then go on a roller coaster that makes you nauseated -- many hours later (I'm told even up to a day later) -- you're likely to become convinced that the sushi made you sick (even if you should know better), and avoid it in the future.
The thing I find fascinating is that it can be conditioned with just one trial, and is strongly resistant to cognitive control. It causes endless problems for chemotherapy patients, who eventually "learn" to associate all sorts of food with sickness, causing nutritional deficits, as if their primary troubles weren't enough.
So the next time you're certain that this or that made you sick, see if you can separate out the feeling of certainty about what caused it. You might not be able to break the feeling that the food certainly caused your sickness, but you should be able to break the certainty itself.