One can imagine that when communicating in person your words alone would cover 99% of what you are saying.
The "Secrets of Body Language" documentary turns this notion on its head and shows that a huge part of your mutual understanding with other people is actually communicated through body language and therefore an important skill to master. Not just in eliquating yourself outwards towards other people but to be good at analysing the body language of others. There Are a lot of ways this can be extremely useful because while a person is speaking one thing their body language could be telling you something entirely different. A skill used extensively by the police in situations which can lead to life or death.
To analyse this The Secrets of Langauge documentary looks at examples in real life, the body language of politicians are particularly prevalent in the film as host David Jeremiah breaks down meetings with the likes of Bill Clinton, Yasser Arafat and Richard Nixon. Showing there are many ways to look at human nature other than just with the words that are being spoken.