Body language is a form of communication, which consists of body posture, gestures, facial expressions, and eye movements. Humans send and interpret such signals almost entirely subconsciously.
While humans primarily communicate via sounds, between 60% to 70% of interpereted meaning of the sounds are dependant on the communicator's body language. As such body language may provide clues as to the attitude or state of mind of a person. For example, it may indicate aggression, attentiveness, boredom, relaxed state, pleasure, amusement, and intoxication, among many other cues. A person's ability to identify these states depends on their familiarisation with the postures. As such it is theoretically possible to interperet an entire conversation simply by observing a person's body language; if they are familiar with the various postures, and further-more, if they are extremely familiar with the language, they can predict or "read" a person's behaviour, thoughts or intentions as they know what the visual cues and postures are and what they mean.
Physical expressions like waving, pointing, touching and slouching are all forms of nonverbal communication. The study of body movement and expression is known as kinesics. Humans move their bodies when communicating because, as research has shown, it helps "ease the mental effort when communication is difficult." Physical expressions reveal many things about the person using them. For example, gestures can emphasize a point or relay a message, posture can reveal boredom or great interest, and touch can convey encouragement or caution.
One of the most basic and powerful body-language signals is when a person crosses his or her arms across the chest. This can indicate that a person is putting up an unconscious barrier between themselves and others. It can also indicate that the person's arms are cold, which would be clarified by rubbing the arms or huddling. When the overall situation is amicable, it can mean that a person is thinking deeply about what is being discussed. But in a serious or confrontational situation, it can mean that a person is expressing opposition. This is especially so if the person is leaning away from the speaker. A harsh or blank facial expression often indicates outright hostility. A woman crossing her arms or hands over her chest is also a way of drawing attention to her breasts as well as a gesture of sexual anticipation.
Consistent eye contact can indicate that a person is thinking positively of what the speaker is saying. It can also mean that the other person doesn't trust the speaker enough to "take their eyes off" the speaker. Lack of eye contact can indicate negativity. On the other hand, individuals with anxiety disorders are often unable to make eye contact without discomfort. Eye contact can also be a secondary and misleading gesture because cultural norms about it vary widely. If a person is looking at you, but is making the arms-across-chest signal, the eye contact could be indicative that something is bothering the person, and that he wants to talk about it. Or if while making direct eye contact, a person is fiddling with something, even while directly looking at you, it could indicate the attention is elsewhere. Also, there are three standard areas that a person will look which represent different states of being. If the person looks from one eye to the other, then to the forehead, it is a sign that they are taking an authoritative position. If they move from one eye to the other, then to the nose, that signals that they are engaging in what they consider to be a "level conversation" with neither party holding superiority. The last case is from one eye to the other and then down to the lips. This is a strong indication of romantic feelings.
Disbelief is often indicated by averted gaze, or by touching the ear or scratching the chin. When a person is not being convinced by what someone is saying, the attention invariably wanders, and the eyes will stare away for an extended period.
Boredom is indicated by the head tilting to one side, or by the eyes looking straight at the speaker but becoming slightly unfocused. A head tilt may also indicate a sore neck or Amblyopia, and unfocused eyes may indicate ocular problems in the listener.
Interest can be indicated through posture or extended eye contact, such as standing and listening properly.
Deceit or the act of withholding information can sometimes be indicated by touching the face during conversation. *Excessive blinking is a well-known indicator of someone who is lying. Recently, evidence has surfaced that the absence of blinking can also represent lying as a more reliable factor than excessive blinking.
Some people use and understand body language differently, or not at all. Interpreting their gestures and facial expressions (or lack thereof) in the context of normal body language usually leads to misunderstandings and misinterpretations (especially if body language is given priority over spoken language). It should also be stated that people from different cultures can interpret body language in different ways.
Cassandra Cain and her mother, Lady Shiva, use their extreme understanding of body language to read and predict the intentions of their opponents. Enabling them to predict their opponent's next move and form counters against them, however, this ability only works if they are familiar with their opponent's body language.
As she was raised specifically to only communicate through body language, Cassandra can also "read" people outside of battle; her extreme familiarity with the language enabling her to identify people by how they walk or stand; even if they change their physical and mental appearance.
Another form of body language is lip reading ("reading" what a person is saying by watching the shapes their mouths make when they talk). Members of the Bat Family are trained to lip read; enabling them to eaves drop on a conversation even if they can not hear the individuals conversing.