Your pupils give you away, and you cannot stop them
You can rehearse your words and even fake a convincing smile, but your pupils are beyond your control. They widen on their own when something or someone interests you. Much of the body's silent signalling works the same way, running below awareness while people talk.
Body language covers the physical side of communication: facial expressions, posture, gestures, eye movement, touch and how people use space. Despite the name, it is not a language in the linguistic sense. It has no grammar and is interpreted loosely, which sets it apart from sign languages, true languages with complex grammatical systems. Its formal study goes by the name kinesics.
Some researchers argue that most of the information exchanged face to face travels this way, helping set up relationships and steer the flow of an interaction, even though it is often ambiguous. Meanings shift between cultures, and while people within one society broadly agree on what particular gestures signal, whether any of it is universal remains disputed. It matters in practical settings too; how a doctor carries themselves affects how openly patients speak.
The roots run deep. Gesture, expression and posture were among the oldest ways primates communicated. Chimpanzees and bonobos inherit some gestures and learn others socially, through a process called ontogenetic ritualization, and people do something similar, as when a raised arm becomes an invitation to a wrestling game. Humans tend to load such signals with richer emotional meaning, while other primates use them more for immediate reactions.
Faces carry a great deal. Scientists once thought a genuine, eye-crinkling Duchenne smile was almost impossible to produce on demand, but a study at Northeastern University found people could fake one convincingly without feeling especially happy. Eyes normally blink around 20 times a minute, a rate that can quicken when looking at someone attractive. Head position adds nuance: tilted up it may suggest pride or contempt, tilted down shame or respect, though context and intensity can reverse such readings.
Source: Body language
