Under normal conditions the act of communication requires the presence of at least two persons: one who sends and one who receives the communication. In order to communicate thoughts and feelings, there must be a regular system of signs or symbols which mean the same to the sender and the receiver.
The means of sending communications are too numerous and varied for systematic classification; therefore, the analysis must begin with the means of receiving communication. Reception of communication is achieved by our senses. Sight, hearing and touch play the most important roles. Smell and taste play very limited roles, for they cannot receive intellectual expression from fully developed systems of signs and symbols.
Examples of visual communication are gesture and mimicry(模仿). Although both frequently accompany speech, there are systems that rely solely on sight, such as those used by deaf and dumb persons. Another means of communicating visually is by signals of fire, smoke, flags, or flashing lights. Feelings may be simply communicated by touch, such as by handshaking or backslapping, although a highly developed system of hand stroking has enabled blind, deaf, and dumb persons to communicate intelligently. Whistling to someone, applauding in a theater, and other forms of communication by sound rely upon the ear as a receiver. The most fully developed form of sound communication is, of course, the spoken language.
The means of communication mentioned so far have two features in common: they last only a short time, and the persons involved must be relatively close to each other. Therefore, all are restricted in time and space.

正常的交谈行为，是在至少两个人在场的条件下进行。一个是交流信息的发出者，另一个是交流信息的接受者。要想进行思想感情的交流，发出者与接受者之间必须存在一种规律的信号系统。
信息发出的方式是多样的，系统的分辨也是不同的，因此信息的理解必须是基于信息接收的方式。信息的成功接收是通过我们的感官来完成地，视觉、听觉、触觉都起着重要的作用，嗅觉和味觉的作用就非常有限了，因为它们不能运用充分发展的信号系统来接收智力信息。
生动的交流过程都是伴随着手势和模仿的，尽管两人语言流利，还是存在着独立的信号（手势）系统，就像聋哑人的手势一样。另一种的有效交流方法是用火、烟、旗帜、闪光等作为信号。情感可以通过接触而直接交流，比如握手、轻拍对方的后背等，因此一种高度发达的手势得以实现，使得聋哑人能够进行智能化交流。对他人的低语、剧院里的鼓掌，都是基于以耳朵为接收者的声音交流方式。当然了，最充分发达的声音交流方式，就是语言了。
到目前所解释的交流方式有着两个共同的特点：它们持续时间短，且交流的双方要在相对近的距离上。因此，都受到时间和空间上的限制。