system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why do we have fear over something even though we know It is not real?
gpt
The older part of your brain doesn't know it's not real.

The part of your brain responsible for fear, the amygdala, is very ancient. It's part of what people often refer to as the "reptile brain," and it evolved to help you avoid things that could hurt you. Even if the conscious part of your brain fully knows something is harmless (like a horror movie you are watching), the response by the amygdala, which is hard-wired, can often be powerful enough to override that.