What does the author say about the speech?

Câu hỏi :

 Although speech is the most advanced form of communication, there are many ways of communicating without using speech. Signals, signs, symbols, and gestures may be found in every known culture. The basic function of signal is to impinge upon the environment in such a way that it attracts attention, for example, the dots and dashes of a telegraph circuit. Coded to refer to speech, the potential for communication is really great. Less adaptable to the codification of words, signs also contain meaning in and of themselves. A stop sign or barber pole conveys meaning quickly and conveniently. Symbols are more difficult to describe than either signals or signs because of their intricate relationship with the receiver’s cultural perceptions. In some culture, applauding in a theater provides performers with an auditory symbol of approval. Gestures such as waving and handshaking also convey certain cultural messages.