 Language acquisition begins very early in the human lifespan. The ascent to adult level competence is a complex process that involves several more or less distinct stages leading from pre-speech sounds to full sentences. These stages have already been discussed in our e-lecture Language Acquisition 1. In this new e-lecture we will describe how the child masters the essential ingredients of his language. In particular we will discuss how the child develops the sound system of the language he or she is exposed to and then we will look at the acquisition of words, that is morphological development. We will outline some central principles of syntactic development and finally we will discuss some stages of the development of the mental lexicon. Let's look at phonological development first. Language development begins with the acquisition of the languages sound pattern. During the first year of life children achieve control of the speech organs, so control of the lungs and the vocal tract. And they develop a sensitivity to the phonetic distinction used in the target language to start out with the innate ability to hear virtually every phonetic contrast used by human languages. For example the difference between voiceless and voiced pairs such as bar versus par. Now with this ability they can later produce almost all sounds of human language, even sounds that play no or a minor role in their target language. Exposure to other language leads to the suppression of non-native speech sounds starting at around the age of 8 to 10 months when most infants show initial signs of word comprehension. So it is this age here. After a period of early vocalization, so this initial period such as crying and cooing, all young children go through a stage of babbling which lasts for about 6 to 9 months, fading out as the first words appear. By producing these speech-like sounds, infants practice their articulatory movements and learn to produce the prosody of their language. There are in fact two types of babbling, reduplicated and non-reduplicating babbling. Now reduplicated babbling examples would be something like bar, where the same syllable is repeated several times and non-reduplicated babbling would be examples of the type ba-da-ga or ba-do-ga and similar syllable combinations. Later on, young children simplify their language and they simplify the words that they produce with a general tendency to produce shorter strings. This simplification occurs in all languages. For example, as far as consonants are concerned, children often omit the final consonant. So instead of using the word ball or bal, they would use something like ba instead. So omission of final consonants or they reduce consonant clusters such as stop and would use something like top instead. As far as syllables are concerned, children often use elements such as mato instead of tomato. So this is a reduction of syllable complexity or they repeat syllables such as da-da and often they substitute more difficult sounds with easier ones. So instead of saying ship, they would say something like sip. So here we have a reduction of the onset of a syllable. Let us look at morphological development next. Morphological development consists of the acquisition of the relevant morphs plus the rules governing their use. That children indeed possess morphological rules has been demonstrated in a classical study in the 1950s which used the so-called wag procedure. Now here it is. The idea was quite simple. Children were instructed like this. Now this is a wag. That was the idea. And then what about this? Here is another one. So you have something like two and then all children answered of course wags. So without having been told that the plural involves the addition of a particular morpheme and here a particular morph they in the vast majority ended up in triggering the correct plural form. Another very important study dealt with the order of acquisition, the order of function words and inflectional morphemes and it has been shown that this is relatively constant across children. For example the present progressive appears first followed by spatial prepositions, by plurals, by possessives, determiners and the past tense in different forms. And this sequence, this order of acquisition was shown to be constant across many children. Let's look at syntactic development next. Now syntactic development starts out with a period of single word speech which may begin as early as 10 months of age. Shortly after the child begins to understand words. At first children's utterances are one word utterances and they do not show any structural properties. They are used to name objects in the environment. Later on during the one word stage children also use single words to articulate complex thoughts involving those objects. So in the one word utterance we have words such as spoon for example in the child's environment or of course words like daddy. And of course here the child already expresses first requests instrumental relationships even on the basis of one word. Around the age of 18 months the holofrastic or one word utterance phase glides gradually into a stage where the child has become aware that adding more words will improve communication and thus starts to produce two word utterances. Here are some examples. So things like want cookie or where daddy are typical examples of this two word utterance stage. At the age of around 20 to 24 months children begin to produce longer and longer utterances that show more complex syntactic patterns. At first these multiple word utterances lack grammatical inflections and function words. This kind of language is then often called telegraphic speech. Here are examples such as cat drink milk or man ride bus. So typical examples of this telegraphic speech phase. From this point onward language development proceeds at a rapid pace. Within only a few months children acquire inflectional morphology and function words. From the age of about two years and six months they produce full sentences of various types and increasing complexity. Before they turn four most children have figured out the salient grammatical patterns of their language. Now what about the semantic development? Well the lexicon as you know from other e-lectures in the field of psycholinguistics is central in human language processing. It provides language users with all the linguistic information they need about a word or to be precise a lexeme including its sound shaped word class valid syntactic contexts and meanings. The lexicon is also central in language acquisition. Words appear first in the acquisition process and knowledge of words provides the basis for the development of sound structure, word structure and syntax. Acquiring a lexicon is an amazing task. It has been estimated that in order to build up an adult size lexicon of about 70,000 entries children have to acquire new words at a rate of something like 10 words per day. Children utter their first recognizable word at around the age of one. The time course of word learning is commonly assumed to involve a vocabulary burst or word spurt roughly six months later. Now we couldn't cover all aspects of language acquisition even in the second e-lecture about language acquisition so there are a number of issues left. For example we will have to discuss what are the driving forces in language development. That is what sort of factors play a role in the acquisition of the child's mother tongue. And how do we know about the child's linguistic competence in other words? How do we collect data? What sort of experiments can we carry out with young children? And finally what are the main strategies involved in the language acquisition process? Well, these and some other issues constitute the backbone of our e-lecture Language Acquisition 3. See you then.