On the Origin of Body Language The Origin of Body Language has a lot to do with the emotions. The emotions are a hot topic of

On the Origin of Body Language
   Hello, everybody. Today’s lecture will focus on "the Origin of Body Language", which is related to the emotions of man. The emotions are a hot topic of the 1990s. They are the most conspicuous difference between the software of our brains and that of computer, creating a puzzle for artificial-intelligence theorists of what a computer would gain if it had emotions as well as a rational calculating ability. The emotional centers of the brain can be almost missing in some brain-damaged patients, creating a puzzle for neuropsychiatrists of what is wrong with these superficially normal people. And social relationships are lubricated, glued together and dissolved by the emotions, creating a puzzle for many of us of how to deploy them efficiently. What does Charles Darwin’s 1872 classic The Expression of the Emotions have to offer here?
   One answer is that emotions are expressed not verbally but in body (and particularly facial) language. You can tell someone is angry, for example, from—in Darwin’s words—" the body being held erect", "the brows being heavily contracted" and "the firmly compressed mouth, the distended nostrils, and flashing eyes". This much was known before Darwin, although his description is more complete and accurate than any of his predecessors.  Indeed, it has not been replaced since.
   Darwin, however, excelled as a theorizer, and The Expression of the Emotions is much more than a body-language dictionary. His main interest was the relation between each emotion and the form of its expression. Why do we express anger by an erect posture and direct stare, rather than by, for example, shrugging our shoulders? His answer is contained in three principles governing emotional expression. Some emotions are expressed in a way that is posturally appropriate for the related behavior. If you are angry, for instance, then you may be about to hit someone and the form of the expression is a postural precursor of doing so: before hitting someone, it makes sense to look at them with some concentration, to tense your muscles, to raise your arm. Darwin called these expressions "serviceable associated habits, "and they are the easiest to understand.
   His second principle, antithesis, is a more remarkable insight. Some emotions appear to be expressed by a posture opposite to that of the opposite emotion. As an example, Darwin used a famous pair of pictures of dogs.  One shows a hostile, threatening dog, expressing its emotion by means of the serviceable associated habits. The other picture is of a subordinate, "humble and affectionate" dog, and its posture—relaxed muscles, body, tail and ears all lowered-is the opposite. Darwin interpreted shrugging the shoulders in the same way. It expresses, he says, helplessness or impotence: "It accompanies speeches such as, ’ It was not my fault’; ’ It is impossible for me to grant this favor’; ’ He must follow his own course, I cannot stop him. ’" In a set of four photographs, he shows how shoulder shrugging is posturally antithetical to someone who is in control or command.
   Darwin’s third principle has never found many supporters (not even Darwin himself). He called it the direct action of the nervous system and used it to explain, for instance, trembling as an expression of fear. Saying that trembling is caused by the direct action of the nervous system  may not be all that enlightening, but I don’t know that anyone has yet thought up anything better.
   The general idea that emotional expression is unique to humans was older still. Social and political theorists of the 18’h century, including Adam Smith, supposed that the Creator had installed blushing in humans to check antisocial behavior and make social life possible. A connection between human emotional expression and social life was a standard, if minor, creationist theme in Darwin’s time. Darwin told Alfred Russel Wallace that he began his emotional project to "upset Sir C. Bell" and to demonstrate the continuity of emotional expression between humans and many other species. This purpose can be detected in the book. But as the project grew it took on new dimensions, and Darwin finally wrote his work up. It was structured around his three principles of emotional expression and not the question of evolutionary continuity.  Nevertheless, he may have avoided discussing communication because it was a creationist hot button that he did not want to push. He could make his argument subtly more persuasive by avoiding it.