In Liu Cixin’s famous science fiction series The Three Body Problem, human beings make first contact with the Trisolarans – an alien civilization incapable of deception or lying because they broadcast their thoughts. This ability creates a deep mistrust of human beings on behalf of the Trisolarans, as our thoughts and agendas are private to our own subjective reality.
Human beings have no foolproof way to know if someone is telling the truth. Sometimes our intuition can give us clues; strange body language, inconsistencies in what people tell us, or their behavior. But apart from this, we are largely left to trust the words of our peers, as we have no way of accessing their own inner world.
This doesn’t mean we haven’t tried. Humans have, and continue to develop techniques that can, in principle, detect when someone is lying.
One of the first known methods to detect lies came ...
