The linguistic variation is inherent to human languages. Be it phonetic, morphological, syntactic, lexical, or prosodic, it is the « fuzzy zone » which allows each individual to express his identity according to, among other factors, his social identity. Within this language variation, the « age variable » which will be reviewed here.
Two preliminary comments must be made. Firstly, the social categories created in our Western societies are typical of these and there is no information on societies which have different age categories ; secondly most of the researches were conducted from the adult age perspective. That is the reason why this stage of life is not treated developementally and why there are only a few cases of research concerning periods of transition into adulthood.
It is in the area of linguistic change that the « age » variable was first used, the differences in the linguistic variables used between two generations being interpreted as an ongoing change. One must remain realistic about the results obtained : first, all changes in speech in a given community do not have the value of a linguistic change, secondly, an ongoing linguistic change can stop, and thirdly, all the linguistic factors identified in synchrony as a linguistic change do not always lead to the expected results in diachrony.
As far as childhood is concerned, most works focus on the acquisition of linguistic norms, or, more generally, on the acquisition of the communicative competence. At this stage, the grammar bases are in conformity with the variety used within the family, and very soon (at 18 months for some linguistic variables) the child uses the social values of language. The peer influence appears around 5 years in the speech of children who, in our societies, are confronted very quickly with school. The sensitivity to social factors is also very precocious, but is not expressed according to adult norms. It is only around 14 years of age that teenagers understand that the linguistic behavior obeys environmental rules.
Teenagers go through a non formal peak before adopting the use of the group that they identify with. From the lexical point of view in particular, the « youth language » is an extremely fertile ground for creation. It changes other aspects of language also, such as syntactical rules. As far as phonology is concerned, it is in the middle of adolescence that the pressure of the linguistic market finally modifies the variants choice of the speakers, to conform them to their profession-to-be. The phonological variants used by teenagers are not chosen according to their parents social status, but reflects the belonging of the teenager to a group who shares the same professional project.
For adults, the linguistic modifications are linked to the various socio-economical conditions and the age of the speaker, the youngest members of the high and upper middle class using the modern variants more frequently. This trend reverses itself in the lower middle class, where the linguistic insecurity leads the oldest members to use the more modern forms. The working class has the same linguistic behavior as the lower middle class, but to a lesser degree. The lowest social category does not take into account the new prestigious forms. Another influential factor is the type of network, those for whom the network is dense and local using more vernacular variants.
There is little research concerning the after retirement period. It seems that the most interesting approach would be one which takes into account the linguistic market change resulting from retirement, and the social category to which the subjects belong. Another approach focuses on accommodation, and the hypothesis of social disengagement gave different results depending on the variable tested.
A longitudinal analysis of the social age effect would allow us to perceive which social variables configuration influences the language of a person at a certain time of his/her life, and, from the opposite direction, to situate our speech on the lifetime continuum. If this configuration is the sole cause of linguistic variations in time then the « age » variable does not exist in itself.