 This e-lecture discusses the driving forces of language development. In fact, various enabling factors for language acquisition have been proposed. They concern positive evidence that is supporting our children during the language acquisition process, the question whether children imitate adult speech and the importance of reinforcing children's utterances. Further questions to be dealt with concern the role of the language we use to address our children, child directed speech, and the debate between nativism and more empirical views of language acquisition. Let us look at the driving factors first. Children definitely have to be exposed to a language in order to acquire it. They need the opportunity to hear and understand words, phrases and sentences within meaningful contexts first before they themselves can begin to produce language meaningfully. Comprehension thus necessarily precedes production in language acquisition. However, the exposure does not have to be direct, that is while it certainly facilitates acquisition, if adults talk to children as they do in most cultures, it is not an absolute requirement. In some cultures, adults do not speak to children at all until the children are using at least some words in a meaningful manner. Could it perhaps be that language acquisition is some sort of imitation of adult language? Well, this would be a very simple explanation of how children learn their language. From this point of view, children just reproduce what they hear. While imitation plays an important role in learning how to pronounce speech sounds and words, this is not true of the larger part of language development. Let us look at some counter-arguments. First of all, children make mistakes that adults wouldn't produce. Here are two examples. A child says something like, mama is a boy, here a girl, or daddy went at home, utterances that we wouldn't produce in this form. Children are creative, they produce novel utterances that were not contained in the adult speech directed to them. And last but not least, children often have imitation problems. That is, they cannot imitate adult utterances if they do not already have heard these in the speech directed to them. So he's going out, the child would still say he go out, cannot imitate this utterance because the child hasn't mastered the combination of an auxiliary and a main verb here. Or when an adult says, say what I say, where can I put them and the answer is where I can put them, then clearly the child hasn't mastered the strategies of question formation. Reinforcement is an important issue in our driving forces. This proposal suggests that language acquisition is basically a process of strengthening and shaping particular behaviors. And these behaviors concern the child's utterances. In fact, there are two types of reinforcement. Positive reinforcement occurs when adults simply support correct utterances. So if the child says that's a dog and this is certainly right, adults would respond with yes to positively reinforce their child. The opposite is negative reinforcement. So as soon as children come up with something that is not in line with adult speech such as the utterance here, she hold it the baby rabbit. No, an adult could respond. She held the baby rabbit. This would be called negative reinforcement. Although this proposal has an appealing simplicity, there is much evidence against the position that reinforcement is a central part of language development. So for example, often adults correct the meaning and not the form. Here is an example where the child uses the term animal farmhouse instead of lighthouse. The next problem is the problem of early comprehension. Some utterances are understood before they are produced, so reinforcement doesn't apply here. And here is another problem, the occurrence problems. Only utterances that have been produced can be reinforced. Thus there is no account for why utterances should occur in the first place. And finally, children start producing the correct forms. Here we have the correct form went. For the past tense, as an example, then they come up with a form that doesn't occur in adult speech. So they replace the originally correct irregular form by a regular form which they think might be the possibility. And later they come up with the final form without being reinforced. Since correct forms are reinforced, the internal stage is not what should happen. Well, in summary, the driving forces discussed do play a role in the acquisition process. In fact, they often interact as shown by this little animation from the virtual linguistics campus. However, they do not constitute the basis for the acquisition process. Could it perhaps be that the way we address our children is the key for language acquisition? Well, parents and those who bring up children all over the world modify their speech when talking to their children. The special way of talking was originally called motherese or alternatively even baby talk. But it is now called child directed speech in short CDS because it is not restricted to mothers. Here are some of the essential properties of child directed speech. First of all, and we all know that child directed speech is phonetically different. It starts with something that you might want to call secondary articulation feature, for example, labialization. As soon as we address young children, we start rounding our lips to address our sweeties. It is phonetically different. It is slower and shorter. It is to a high extent simplified. We use fewer affixes. That is, the inflection is simplified. The vocabulary is restricted. We use baby words such as moo moo. And we clearly segment the utterances to make them audible in a much better way for the children to who we talk. And often it is more exaggerated in intonation. It is higher pitched. We often use a high pitch in order to make things more expressive. And sometimes it's just strange, isn't it? Why don't we use pronouns to address ourselves? Why do we say things such as daddy will be with you soon, my dear? Well, furthermore, many parents also expand their child's incomplete utterances into appropriate full sentences or paraphrase a given utterance. Some sort of reinforcement, if you wish. Generally, it has not been shown that children whose parents use child directed speech pass through the milestones of language development any faster. But having said that, children certainly benefit from their parents speaking slowly, clearly and succinctly to them. The final issue we have to discuss is the question about innateness. A major issue in the study of language development concerns the extent to which our language abilities are innate. Well, the main claim is that language capacity is present from birth that we use some sort of special purpose language acquisition device, universal grammar, and that language acquisition is just the setting of some central parameters. The controversy centered on this issue is known as the nature versus nurture debate. Whereas the nativist approach believes that language acquisition is based on some innate mechanisms, the empiricist view favors an approach whereby language, like many other aspects of knowledge, derives from experience. So these are then the two extremes, nativism versus empiricism. More recently, a third position emerged which is between these two extremes. It acknowledges that there are certain innate abilities that make language development possible. But in contrast to the nativist view, it argues that these abilities are not specific to language, so it's somewhere in the middle. Well, after three e-lectures on language acquisition, we should have got some basic understanding of the enormous complexity of this field. Yet there are further issues we have to solve. How do we know about the child's linguistic competence especially at an early stage of language development? What are the main strategies involved in the language acquisition process? These and some other questions constitute the starting point of our e-lecture Language Acquisition 4.