system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: Why do we puke when we *see* something disgusting, although there's no sign it has actually entered or interfered with our body?
gpt
We have a very vivid sensory imagination, and it's pretty common that our bodies get their signals crossed a bit and respond in real ways to imaginary stimulus. For some of us, seeing someone get hurt badly can give us 'sympathy pains' in the same body part. For a lot of people, looking at or even *thinking* about a lemon, is enough to make their tongue and salivary glands tingle. It's the same with our disgust reactions.

Neurologically, we don't have a super deep explanation for this, but we know that there are these things called "mirror neurons" in humans and many other animals, which fire both when we do something *and* when we see someone else do the same thing. We seem to have some part of our brain and central nervous system which is basically hard-wired for the purpose of imagining ourselves in someone else's place. There are lots of evolutionary reasons why this might be the case.