Language structure: psychological and social constraints

There are around 5.000 spoken languages of the world today, and they are all different. Thus, natural languages are very diverse. However, most linguists share the view that the languages of the world, and the way they are used in different communities, have a lot in common. The properties that all languages have in common are called language universals. Linguists have claimed of many different (kinds of) things that they are language universals. For a simple example of a syntactic universal, it has been claimed that all languages spoken by humans have, and make a distinction between, nouns, verbs, and modifiers. Simple phonological universals have it that all languages have oral vowels, and that no langauge has the three vowel system /i/-/e/-/u/. Some simple semantic universals are that all languages have color words for what we call ‘black’ and ‘white’, and that we don’t have color words for interrupted spaces in the color vector space. Another one says that all languages have simple lexical items to express, for instance, negation, conjunction, and disjunction, mood, universal quantification, simple past, deontic necessity, and the comparative relation. These universals are all rather surfacy, stated in absolute terms, and categorial (not about use). As long as one stays at this superficial level, what is shared by languages is rather limited. There are various ways, however, in which these limitations can be overcome. Language universals can be stated in implicational rather than absolute terms, they can be stated in more abstract terms making use of a hidden structure (like phrase structure trees, and other abstract representational levels), and finally, they can be formulated in terms of tendencies or frequency distributions rather than in categorial terms. Within typological research going back to Greenberg (1963) most universals are rather