system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it that when you start hanging out with someone a lot you eventually begin to talk like them, even without realizing it?
gpt
Humans are social animals. Which means, unlike cats for example, we are not born with many neurological instincts on how to behave. From birth, we copy others to learn behavior. It's a crazy thing and we don't even consciously realize we're doing it. Spending a lot of time with someone will often cause is to mimic what they do because it helps us relate to each other and further a social relationship. When you find yourself talking and acting like someone else, chances are they're mimicking you as well.

Fun fact, this can also be used to your advantage. If you just met someone, mimic their movement and speech. They'll be much more open and comfortable with you.