system
Given the following post, respond as if you're commenting on Reddit:
human
Why do my hands get sweaty when I watch people climb?
gpt
Same reason you can feel someone else's pain when they get hurt, e.g. Guys can feel another guy's pain when he gets kicked in the testes. 
We have mirror neurons in our brain. When you do a certain activity or feel a certain emotion, a network of neurons in your brain fire. Now when you see someone who is doing this activity or going through this emotional experience, a subset of those neurons fire in your brain! 
This probably evolved so that we can feel empathy and relate to what other people are going through, since this is important for living in large societies like humans do.