There are forms of verbal communication along with sign language and speech language. Facial expression, manual gesture, vocal gesture, and other forms are equally powerful in conveying communication.
Body language consists of posture, facial expression, gesture, and eye contact. Psychologists say that a person's impact depends 7% on what is said, 38% on how it is said and 55% on body language. That is, social anthropologist Edward T. Hall claims that 60 percent of all communication is non-verbal.
More than often, when you observe anyone who speaks, notice how their manual and vocal gestures reveal something "between the lines". When observing, virtually everyone talks with manual gesture, consciously or unconciously. Hearing Italians, Brazilians, and some Latin Americans are more fluent in manual gesture than some of other groups. As these people are expressive in manual gesture in conversation, more than often, deaf people find that communication with these people is relatively easy.
A meaning of a particular gesture can be either abstract (e.g. spontaneous) or semiotic (conventionalized). Manual gestures vary from culture to culture and individual to individual. As a result of the globalization, cultural gestures may be evolved, altered, or traditional that people might be more aware of cultural differences.
David Armstrong, William C. Stokoe, and Sharman E. Wilcox (ASW for short). Gesture and the Nature of Language.
Axtell, Roger E. Gestures: The Do's and Taboos of Body Language Around the World. John Wiley & Sons, 1991.
McNeill, David. Hand and Mind: What Gestures Reveal about Thought. The University of Chicago Press, 1992.
Morris, Desmond et al. Gestures: their origins and distribution. London, 1979.
O'Carroll, Eoin. Foreign gestures aren't what they seem, November 5, 2001.