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Human language is qualitatively and quantitatively different from the communication systems of all other species of animals. Linguists have long tried to create a working definition that distinguishes it from non-human communication systems. Linguist Charles Hockett’s solution was to create a hierarchical list of what he called design features, or descriptive characteristics, of the communication systems of all species, including that of humans.2 Those features of human language not shared with any other species illustrate exactly how it differs from all other species.

Hockett’s Design Features

The communication systems of all species share the following features:

  1.  A mode of communication by which messages are transmitted through a system of signs, using one or more sensory systems to transmit and interpret, such as vocal-auditory, visual, tactile, or kinesic;
  2. Semanticity: the signs carry meaning for the users, and
  3. Pragmatic function: all signs serve a useful purpose in the life of the users, from survival functions to influencing others’ behavior.

Some communication systems (including humans) also exhibit the following features:

  1. Interchangeability: the ability of individuals within a species to both send and receive messages. One species that lacks this feature is the honeybee. Only a female “worker bee” can perform the dance that conveys to her hive-mates the location of a newly discovered food source. Another example is the mockingbird whose songs are performed only by the males to attract a mate and mark his territory.
  2. Cultural transmission: the need for some aspects of the system to be learned through interaction with others, rather than being 100 percent innate or genetically programmed. The mockingbird learns its songs from other birds, or even from other sounds in its environment that appeal to it.
  3. Arbitrariness: the form of a sign is not inherently or logically related to its meaning; signs are symbols. It could be said that the movements in the honeybees’ dance are arbitrary since anyone who is not a honeybee could not interpret their meaning.

Only true human language also has the following characteristics:

  1. Discreteness: every human language is made up of a small number of meaningless discrete sounds. That is, the sounds can be isolated from each other, for purposes of study by linguists, or to be represented in a writing system.
  2. Duality of patterning (two levels of combination): at the first level of patterning, these meaningless discrete sounds, called phonemes, are combined to form words and parts of words that carry meaning, or morphemes. In the second level of patterning, morphemes are recombined to form an infinite possible number of longer messages such as phrases and sentences according to a set of rules called syntax. It is this level of combination that is entirely lacking in the communication abilities of all other animals and makes human language an open system while all other animal systems are closed.
  3. Displacement: the ability to communicate about things that are outside of the here and now made possible by the features of discreteness and duality of patterning. While other species are limited to communicating about their immediate time and place, we can talk about any time in the future or past, about any place in the universe, or even fictional places.
  4. Productivity/creativity: the ability to produce and understand messages that have never been expressed before or to express new ideas. People do not speak according to prepared scripts, as if they were in a movie or a play; they create their utterances spontaneously, according to the rules of their language. It also makes possible the creation of new words and even the ability to lie.

A number of great apes, including gorillas, chimpanzees, bonobos and orangutans, have been taught human sign languages with all of the human design features. In each case, the apes have been able to communicate as humans do to an extent, but their linguistic abilities are reduced by the limited cognitive abilities that accompany their smaller brains.


Languages we do not speak or understand may sound like meaningless babble to us, but all the human languages that have ever been studied by linguists are amazingly similar. They all share a number of characteristics, which linguists call language universals. These language universals can be considered properties of the Universal Grammar that Chomsky proposed. Here is a list of some of the major ones.

  1. All human cultures have a human language and use it to communicate.
  2. All human languages change over time, a reflection of the fact that all cultures are also constantly changing.
  3. All languages are systematic, rule driven, and equally complex overall, and equally capable of expressing any idea that the speaker wishes to convey. There are no primitive languages.
  4. All languages are symbolic systems.
  5. All languages have a basic word order of elements, like subject, verb, and object, with variations.
  6. All languages have similar basic grammatical categories such as nouns and verbs.
  7. Every spoken language is made up of discrete sounds that can be categorized as vowels or consonants.
  8. The underlying structure of all languages is characterized by the feature duality of patterning, which permits any speaker to utter any message they need or wish to convey, and any speaker of the same language to understand the message.