Primates have been able to learn simple language. However, this may not actually be language use and comprehending as they do not use complex grammar (1), lack social-cognitive abilities that allow for language learning (2) and lack a theory of mind (3). Language may have co-evolved with social intelligence.

Language refers to the systematic and conventional use of sounds, signs or written symbols for the intention of communication or self-expression. Human language differs from the communication of other animals in three ways:

• Human language is symbolic (i.e. it represents something independent of the sound)
• Human language is grammatical.
• Human language varies with culture.\

There are seven functions of language:

1. Instrumental (i.e. express needs).
2. Regulatory (i.e. tell others wat to do).
3. Personal (i.e. express feelings, opinions and individual identity).
4. Interactional (i.e. make contact and form relationships).
5. Heuristic (i.e. gain knowledge about the environment).
6. Imaginative (i.e. tell stories and jokes to create an imaginative environment).
7. Representational (i.e. convey facts and information)

Language consists of phonology (1), morphology (2), syntax (3), semantics (4) and pragmatics (5).

Phonology refers to the sounds of a language. There are age-related changes in the tongue, mouth and the larynx which allow for producing sounds. There are several stages of phonological development:

1. Reflexive crying and vegetative sounds (0 to 8 weeks)
2. Cooing and laughter (8 to 20 weeks)
3. Vocal play (16 to 30 weeks) (i.e. uttering single syllables with vowel or consonant sounds)
4. Reduplicated babbling (25 to 50 weeks) (e.g. bababa)
5. Jargon (9 to 18 months)

Babbling consists of many non-repeated consonant-vowel patterns. Jargon babbling refers to strings of sound filled with a variety of intonations and rhythms to sound like meaningful speech. Speech production driven before 6 months of age is driven by internal forces rather than the environment. Babbling may have the function of socially relating to family members and it may reflect infants’ sensitivity to and production of patterns in the linguistic input. Phonemic awareness refers to the knowledge that words consists of separable sounds. This is important in proficient reading and phonemic awareness may improve by learning to read.

Morphology refers to the structure of words and to a system of rules for combining units of meaning into words (e.g. adding ‘ed’ to a word makes it past tense). A morpheme refers to the smallest unit of meaning in a language. Free morphemes can stand alone as words (e.g. fire; run). Bound morphemes cannot stand alone and are attached to free morphemes (e.g. the letter ‘s’). The mean length of utterance refers to the average number of morphemes a child uses in a sentence and is indicative of children’s linguistic development. Many of the morphemes children learn are word endings and they tend to show overregularization (i.e. overusing a rule; ‘s’ for every word that is plural).

The wug test shows children a series of unfamiliar objects or pictures of people performing unfamiliar actions and tie pseudowords to these objects or actions (i.e. ‘this is a wug’). Children then have to extend the word from singular to plural and this will show whether a child knows the morphological rule of the language.  

Syntax refers to a system of rules for creating phrases and sentences out of words. Holophrases refer to one-word sentences (i.e. single words with different intonations to convey different meanings). Children initially only use meaningful words and omit languages that make language easier to understand but are not necessary (e.g. ‘daddy give milk me’). This is called telegraphic speech. Children begin to produce more complicated sentences aged two and children use complex sentences by four years of age.

Children typically learn about negatives at two years of age. Questions develop from adding a raised intonation at the end of declarative sentences to more adultlike forms. The ‘wh’ questions begin during the third year. Children learn about passive sentences around the age of 5 or 6. The basic grammatical structure of school-age children’s sentences varies little from that of adults.

Semantics refer to the meaning of language terms. Vocabulary is one indication of children’s semantic development. Children speak their first words at about 10 to 12 months of age. At 18 months of age, the rate at which they learn new words increases substantially (i.e. word spurt). Most words children learn here are labels for objects. However, some children may experience a more gradual development of vocabulary. Children first rapidly learn words in their receptive vocabulary before they learn it for their productive vocabulary. Fast mapping refers to the ability to learn new words based on very little input and this may underlie the word spurt. The word spurt is associated with a special processing ability (i.e. fast mapping).

There are several lexical constraints that influence word learning:

1. Whole-object assumption
   This states that children assume that a new word refers to the whole object when they hear it.
2. Taxonomic constraint
   This states that children assume that words refer to things that are similar (i.e. two animals that look like rabbits are rabbits).
3. Mutual exclusivity assumption
   This states that different words refer to different things.
4. Syntactic bootstrapping
   This states that children get an idea of the meaning of a word through its grammatical form.

Joint attention may be an important mechanism which gives rise to word learning. However, children are prepared to learn words.

Overextensions refer to stretching a familiar word beyond its correct meaning (e.g. ‘bird’ for everything that flies). This may be a strategy to get adults to provide them with the correct word. Underextension refers to the phenomenon of having a too strict category for a word (e.g. only one’s cat is a cat and other cats have a different name).

Pragmatics refer to how language is used in a social context (e.g. different tones to a classmate or teacher). Children need to learn that good messages have the right quantity of information (1), is at the proper level of description (2), are truthful (3) and relevant to the present context (4). Another important issue of pragmatics is turn taking. Speech registers refer to different styles of speech (e.g. different style of speech at home and at school). A speech register at home that differs from school (i.e. in the case of dialects) can lead to educational difficulties (e.g. at home: ‘we be vibin’). Children have the ability to make most of their wants and feelings known by age 5 or 6 but their ability to communicate effectively continues to increase with age.

Communicative competence refers to the overall mastery of language (i.e. all separate aspects). Children’s early speech may be egocentric. Collective monologues refer to egocentric exchanges (i.e. speaking with but not necessarily to one another). Children typically have metacognitive deficits. This means that they have a poor understanding of message quality and its role in determining the success or failure of a communication. Children often also find it difficult to monitor their own speech. Assessing children’s self-monitoring abilities can be done by examining the frequency with which they correct their speech (e.g. verbal repairs). The incidence of verbal repairs is low in young children’s speech because of poor self-monitoring skills. Verbal repairs increase during middle childhood and decreases in adolescence as skills such as planning improve.

Children’s speech is not always egocentric and there is greater metacommunicative competence when the messages are embedded in familiar scripts. Communication abilities develop first in highly specific, familiar situations and are easily disrupted. With age, children display their communication skills in increasingly diverse contexts.

Behavioural theories state that children learn language through the principles of classical and operant conditioning. In this model, parents are reinforcers for language. However, this theory is unlikely to account for language learning. Statistical learning refers to a domain-general mechanisms to discern what is a word and what is not a word. In statistical learning, infants keep track of how often different syllables follow one another and use this information to determine whether sound frequencies are meaningful. While there is some evidence for this, it may be a domain-general ability and not specific to language learning.

Nativist theories hold that children are biologically prepared to learn language and do so with innate learning mechanisms. Social interactionist theories state that humans are biologically prepared to acquire language but aspects of the environment (e.g. parents) specifically foster language acquisition.

The deep structure of language refers to the underlying meaning of language. Chomsky states that languages share this deep structure and innate knowledge about this allows a child to learn a language. He proposed the language acquisition device (LAD). Lenneberg states that language is a special huma ability with a strong biological basis because of the following characteristics of language:

• Language is species specific.
• Language is species uniform (i.e. all normal members possess language).
• Language is difficult to retard (i.e. nearly all children are able to learn language).
• Language develops in a regular sequence.
• There are specific anatomical structures for language.
• There are genetically-based language disabilities.

Wernicke’s area, located in the temporal lobe, is associated with comprehending speech. Broca’s area, located in the frontal lobe, is associated with speech production. Recovery of language function is often good when damage occurs in infancy or early childhood compared to when it occurs later in life. There may also be a grammar centre in the brain. Children’s brains are especially sensitive to language. Different areas of the brain are involved when a second language is learned in childhood versus in adolescence or adulthood though there is not necessarily a difference in fluency.

It is possible that children have universal grammar which refers to innate knowledge about the syntax of language and consists of the basic grammatical rules that typify all languages. Evidence for this comes from the existence of pidgins (i.e. combined ‘language’ of group of people with different native languages) and creoles (i.e. created language within a generation, by children, based on the pidgins). This means that children invented language when necessary and shows some evidence for the existence of universal grammar. There may be a critical period of language development. Children need to be exposed to language early in life if they want to master it. Younger children are better at learning a second language than older children and adults. Grammatical proficiency is related to age of first exposure to sign language and not the number of years one has been using the language.

The less is more hypothesis states that cognitive limitations of infants and young children simplify the body of language they process making the complicated syntactical system of any language easier to learn. Children’s limited information processing abilities reduce the complexity of what they must master and this results in easier initial acquisition.

The social pragmatic view of language acquisition states that while children are biologically prepared for learning language, the environment is important and helps. For example, the content and the presentation of language is adjusted to their abilities. It holds that language is a powerful social-cognitive tool which can be used to manipulate other people’s attention.

It is possible that joint-attention activities between children and caregivers provide the context for effective communication in which language will emerge. Children who engage in joint attention activities early tend to begin talking early. The gesture facilitation hypothesis states that the use of gestures facilitates the acquisition of spoken language (e.g. gestures can be used to get attention to something which is then paired with a verbal component). Gestures could cause parents to say words and sentences that children need to expand their speaking abilities or children who use gestures may have better cognitive skills which allows for easier language learning. Thus, treating other people as intentional beings (e.g. shared attention) is the social-cognitive foundation for language development.

Motherese (i.e. child-directed speech) includes high-pitched tones (1), exaggerated modulations (2), simplified forms of adult words (3), many questions (4) and many repetitions (5). It is possible that adults have a language acquisition support system (LASS) which responds to infants and young children by automatically altering speech to a more understandable form. Infants prefer motherese. When motherese is used, infants can discriminate between words that have very slight differences in sound.

Motherese may teach children about language (i.e. syntactic development) but it may also promote the emotional relationship between the infant and the caregiver. Motherese may be used to regulate the child’s emotions. There are different acoustic patterns in motherese which convey the mother’s approval (1), express prohibition (2), ask for attention (3) and provide comfort to the infant (4). This may help in promoting a secure attachment and this is beneficial in the development of language.

Children receive a highly simplified body of language in the early stages of language development. In combination with the limited information-processing abilities, it is easier for children to learn language. However, motherese may not be necessary for language acquisition though only adult-directed speech without a social component is not sufficient to learn a language.

Bilingualism refers to being fluent in two languages. Simultaneous bilingualism refers to children being exposed from birth to two languages. Sequential bilingualism refers to children who learn a second language after mastering their first. Simultaneous bilinguals often experience rarely any interference between the two languages, bar the occasional mistake, but do have smaller vocabularies in both languages and a slight delay in syntactic development. However, these differences are minimized by the age of 8 or 9. Bilinguals of all ages are slower than monolinguals at retrieving individual words from their long-term memories.

Bilingual children often have greater cultural sensitivity (1), recognize more phonemes (2), have higher levels of metalinguistic awareness (3) and have enhanced executive control (4). Semi-lingualism refers to a lack of mastery in either language.

Caregivers talk more and use more supportive speech with daughters than with sons. The content also differs. Emotion talk is more frequent in young girls. However, it is likely that gender differences in language development exist due to cultural differences. One difference that is found is that girls are more advanced in their narrative production than boys. The greater prenatal exposure to testosterone, the smaller the child’s vocabulary is. Girls may be more vocal in infancy and this may give an advantage in learning a first language though this is not necessarily true.

Language is used to express thought but is not thought itself. The ability to use language may transform a child’s thinking and the use of language in social situations may facilitate this transformation. According to Vygotsky, thought and speech have different roots in development but they merge in development and becoming interdependent. Egocentric speech (i.e. private speech) refers to speaking to oneself. This may help children organize their thoughts as they cannot use language covertly (i.e. in their heads) yet. Private speech serves as a cognitive self-guidance system. Private speech eventually gives way to inner speech. Children rely more heavily on private speech when facing difficult rather than easy tasks.