Not everything is political BS. Some things are just common sense. People can read body language and sometimes they can tell if someone is lying, especially if they know the liar well.
I can usually tell when my 3 year old daughter is lying because either her speech is quieter, or she acts excessively generous. It also helps that she always blames one of the dogs, typically a stuffed one.
It's funny the stuff she thinks she needs to sneak. A couple weeks ago I stumbled upon her in the back bedroom, shamefully eating a graham cracker. We celebrate her willingly eating anything that isn't pure sucrose...
“Common sense” is just a modern positive term for folk mythology; and particularly when it comes to reading “body language” to detect lies, much of that popular wisdom is based on fabrications deliberately popularized by the law enforcement community (not unlike polygraphy, and, until the same fell apart, the FBI’s “fiber science”.)
Relying on body language (not independent knowledge of the facts of the claim) to detect lies is at best barely better than a coin flip and tends to rely (like polygraphy, which is also not reliable) on indicators of arousal and the known false assumption that arousal = deception, but with less accuracy in detecting arousal than a polygraph.
