What is a mother tongue?
By definition, the mother tongue is the language that a child learns in earliest childhood without formal instruction. Linguists regard the term 'mother tongue' as imprecise, because it is less about the person of the mother than about a speaker's linguistic and cultural roots. Therefore, experts often use the term 'first language' or the English term 'native language'. What is crucial for the mother tongue is the early and constant contact with the language, through which sounds and grammatical structure become so deeply ingrained that the child masters the language automatically.
Mother tongue vs. first language:
The terms mother tongue and first language are synonymous — although the first language a child learns does not necessarily have to be the language spoken by their mother. The term mother tongue emphasizes the aspect that children's language acquisition begins already in the womb, while the designation first language is more precise — it is the language a child learns first and intuitively. Accordingly, children raised bilingually learn two first languages, provided that they use both languages in everyday life and have a similar level of proficiency in both.
How babies acquire language
Recognizing and selecting sounds: Even newborn babies can perceive a large number of different phonemes (language-characteristic sounds). Immediately after birth, a baby begins to perceive the characteristics of its mother tongue by hearing its parents speak in various everyday situations. In doing so, it filters out the most frequent sound patterns and learns to recognize certain speech rhythms.
'Sound inventory' and speech modulation: By 6-9 months, babies know all the characteristic sounds of their mother tongue. They can also perceive changing pitch and speech rhythm, for example when parents coo to them, speak angrily, or play. Although the baby does not yet know the connection between words and their associated objects, it begins to imitate certain sounds and parts of words.
First words: Around one year, a child begins to grasp the connection between words and objects or states. The first words are often used broadly for several things (e.g., 'ball' for anything that is round).
Object, verb, subject. As soon as a child perceives itself as a person and the environment as objective — for example in the second half of the second year of life — it begins to assign words correctly and to use verbs, sometimes already in two-word sentences. Children often refer to themselves by their given name at this age to express states: 'Lisa hungry' or 'Max ouch'.
Speaking and understanding: By three to four years, a child knows all the basic structures of its mother tongue in terms of grammar, phonetics and speech rhythm. It also articulates long words and uses sentences with subject, predicate and object.
Theories of child language acquisition — does the mother tongue play a role?
Chomsky's theory of universal grammar: A well-known theory of linguist Noam Chomsky states that all languages spoken worldwide share common grammatical principles and that every person internalizes these principles from birth. Thanks to this innate 'universal grammar', children do not have to learn all grammatical rules during language acquisition, but only the specific realizations of their mother tongue.
Cultural theories as a basis for language acquisition: More recent research on language acquisition contradicts the assumption of innate grammatical structures as proposed by Chomsky. Supporting evidence is the finding that the part of the cerebrum responsible for language acquisition is highly developmentally plastic in early childhood. Because children usually receive a great deal of very specific linguistic input from their environment in the first years, they develop an intuitive understanding of the grammatical structures and sound patterns of their mother tongue.
Parental support in learning to speak: The U.S. psychologist Jerome Bruner proposed in the 1980s that the linguistic environment and parental interaction play a decisive role in children's language acquisition. Building on Chomsky's theory of universal grammar, Bruner proposed the idea of a parental language acquisition support system (Language Acquisition Support System, LASS).
