Studying a person's eye movement is often suggested to reveal information relating to his imagination, information recall and dishonesty. For instance, if an individual tended to move his eyes towards the right of his head, this is associated with the notion that his mind is "creating" something; this creation isn't necessarily lying, as in some contexts this can be associated with producing an idea or an imaginative thought. Eye movement has also been used to determine when a person is frustrated, rationalizing behavior, remembering sounds or showing excitement, among others.
As the mouth is fundamentally linked with language and expression, it is often studied by body language interpreters. For example, when a person expresses a tight-lipped smile (noticeable for being straight and not exposing teeth) it indicates that something is being kept secret or unrevealed, often for reasons of not trusting the other people around. Facial movement reveals feelings of self-comfort, tension or frustration, depending on the expression.
Use of the head is often common for widely understood body language, such as shaking to demonstrate disagreement or tilting to one side to express thoughtfulness. Head movements can also suggest confidence (such as when somebody raises his chin slightly) and paying attention (when the head is slowly or timely nodded while another person is talking). However, these movements can be subtle -- while nodding can suggest agreement, fast-paced nodding can be a subtle way of expressing impatience.
Arms are a particularly interesting element of body language, as they're often specifically noticed in relation to a person demonstrating feelings of nervousness or insecurity; only in one notable instance, when arms are held and clasped behind a person's back, do they actively suggest confidence. Defensive arm movements are related to "blocking" the person's body from the other person -- these include folding arms, holding objects in front of the chest and adjusting bracelets or watches, among others.
Hands are perhaps the most studied aspect of body language, as their use for communicating is unparalleled by any other part of the body. In contrast to studying other aspects of body language, movement of the hands is said to suggest a huge range of feelings and states; for example, tugging on the ear can signal indecision, cracking knuckles can signal the desire for attention and open palms can suggest submissiveness or openness.