An animate individual has one set of properties which it shares with all members of its species and another set which it only shares with a group or which render it unique. The former are innate. For the latter, the question arises whether or to what extent they are innate or acquired during maturation, thus due either to heritage or to socialization. This alternative applies to language, too. Since it is ideologically laden, it has a name of its own, the nature-nurture dichotomy.

Although this is not actually an either-or issue, but rather one of proportions, both polar positions have had their advocates.

• At one extreme, there is the behaviorist position. It roughly says: A child is born with a neural equipment which enables him to imitate, assimilate, learn and exercise many diverse capacities. The infant applies this endowment to whatever he perceives and is motivated to learn, including language. Thus, although all human beings share the capacity for language, there is no particular mental organ responsible for it. The entire language capacity is acquired by behavioral conditioning in a combination of stimuli and responses (Skinner 1957).
• At the other extreme, there is the generativist position. It roughly says: A child is born with a specific mental organ which enables him to construct an internal representation of any language system if he is exposed to data representing it. This organ is the language acquisition device or, in terms of theory of grammar, universal grammar. It comprises everything which all languages have in common. All the learning child has to do is some parameter settings for the language of his environment; which explains why he can learn it in so short a time and including formal operations which he could not abstract from the data that he is exposed to (Chomsky 1995).

Much research has been done on the basis of both of these extreme positions. Like many other extreme positions, they are equally sterile:

• Against the behaviorist position, it is a proven fact that human brains come with specific capacities for semiosis and semiotic operations which distinguish them from animals and which adapt to the specifics of human language at a very early age.
• Against the generative position, it is a proven fact that normal primary language acquisition is fostered by extensive and dedicated teaching by caretakers and that children differ considerably in their language competence in consequence of the different quality of the input they receive. More on this in the section on primary language acquisition.

Thus, after more than half a century of psycholinguistic research, the question of what exactly is innate about the human language capacity is still subject to empirical research.