system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why do our bodies produce tells and signals when we lie?
gpt
Lying is stressful!

Not only are people conditioned by society not to lie, but the situation that you feel requires a lie (whether that be a small lie such as “you look great in that dress” or a big one like “I did not kill that man”) is generally a stressful one. Furthermore, you’re often thinking about what will happen if you’re caught in it.

In other words, they’re not lie signals at all- they’re stress signals. And humans are social creatures for whom stress signals form an important part of social signaling.