Body language analysis has long been a theme in popular books, traditional media and now, an increasing number of YouTube channels. While this is all pretty entertaining, it's not scientific: It’s really, really hard to study body language.
To express yourself without words, you mostly use your head and your hands. But many actions of your hands and body are so idiosyncratic that they carry little specific meaning. So, popularly, people prescribing an intention to a movement that, perhaps, had no intention at all.
And therein lies the problem: researchers need to encode and decode your movements to study them. If you do A, it could mean B or C. A lot of research is open to interpretation, but this idea of "intention" can be very subjective – especially when our body language can shift due to our age, culture and gender. We can't study something empirically if we're making guesses at what a movement means, or if it means anything at all.