Another basic contribution of contemporary research to the problem of linguistic change is the establishment of a relation between the frequency of a linguistic unit and its form, so that a change in frequency may involve a change in its phonic aspect. This, a consequence of the theory of selective information, applies to units of both articulations, to phonemes as well as to monemes. It leads to the conclusion that since the rise in the fequency of a unit is nothing but a rise in the number of times that unit is used, any use of a linguistic unit contributes, even if only in an infinitesimal way, to an increase in its frequency. This automatically entails a lowering of its contribution to information and a tendency to reduce its cost, that is the output of energy it requires for its memorizing and production. Such a reduction is likely to determine changes in the phisical aspect of the unit. This could be summerized by saying that, strange as it may sound, a language changes because it is used. People as a rule are not conscious of any change taking place in their language.
- Martinet (1962), a pag.135-136