Can technology be used to predict if people are lying? How do you know this?

Actually, yes it can! A polygraph is used by measuring your heart rate, blood pressure, etc - It pretty much reads your vitals I suppose. They ask you a bunch of questions, and if they see any of spikes, they know you're lying. But, you have to be careful not to move - or it can affect your answers.

A way you could say you know this is by saying there are jobs for people that read them (I think they make some GOOD money from it too)  

I hope this somehow helps!

answerdmz;