Language development

Language development in humans is a process which starts early in life. Infants start without knowing a language, yet by 10 months, babies can distinguish speech sounds and engage in babbling. Some research has shown that the earliest learning begins in utero when the fetus starts to recognize the sounds and speech patterns of its mother's voice and differentiate them from other sounds after birth.

Children develop receptive language abilities before their verbal or expressive language develops. Receptive language (language perception) enables internal processing and understanding of language. For instance, six-month-old infants understand the meaning of basic words (such as banana or hand).

Expressive language (language production) is considered to begin with a stage of pre-verbal communication in which infants use gestures and vocalizations to make their intents known to others. According to a general principle of development, new forms then take over old functions, so that children learn words to express the same communicative functions they had already expressed by proverbial means.

Children learn syntax through imitation, instruction, and reinforcement.

Theoretical frameworks

Language development is thought to proceed by ordinary processes of learning in which children acquire the forms, meanings, and uses of words and utterances from the linguistic input. Children often begin reproducing the words that they are repetitively exposed to. The method in which we develop language skills is universal; however, the major debate is how the rules of syntax are acquired. There are two quite separate major theories of syntactic development: an empiricist account by which children learn all syntactic rules from the linguistic input, and a nativist approach by which some principles of syntax are innate and are transmitted through the human genome.

The nativist theory, proposed by Noam Chomsky, argues that language is a unique human accomplishment, and can be attributed to either "millions of years of evolution" or to "principles of neural organization that may be even more deeply grounded in physical law". Chomsky says that all children have what is called an innate language acquisition device (LAD). Theoretically, the LAD is an area of the brain that has a set of universal syntactic rules for all languages. This device provides children with the ability to make sense of knowledge and construct novel sentences with minimal external input and little experience. Chomsky's claim is based upon the view that what children hear—their linguistic input—is insufficient to explain how they come to learn language. However, because children possess this LAD, they are in fact, able to learn language despite incomplete information from their environment. Their capacity to learn language is also attributed to the theory of universal grammar (UG), which posits that a certain set of structural rules are innate to humans, independent of sensory experience. This view has dominated linguistic theory for over fifty years and remains highly influential, as witnessed by the number of articles in journals and books.

The empiricist theory suggests, contra Chomsky, that there is enough information in the linguistic input children receive and therefore, there is no need to assume an innate language acquisition device exists (see above). Rather than a LAD evolved specifically for language, empiricists believe that general brain processes are sufficient for language acquisition. During this process, it is necessary for the child to actively engage with their environment. For a child to learn language, the parent or caregiver adopts a particular way of appropriately communicating with the child; this is known as child-directed speech (CDS). CDS is used so that children are given the necessary linguistic information needed for their language. Empiricism is a general approach and sometimes goes along with the interactionist approach. Statistical language acquisition, which falls under empiricist theory, suggests that infants acquire language by means of pattern perception.

Other researchers embrace an interactionist perspective, consisting of social-interactionist theories of language development. In such approaches, children learn language in the interactive and communicative context, learning language forms for meaningful moves of communication. These theories focus mainly on the caregiver's attitudes and attentiveness to their children in order to promote productive language habits.

An older empiricist theory, the behaviorist theory proposed by B. F. Skinner suggested that language is learned through operant conditioning, namely, by imitation of stimuli and by reinforcement of correct responses. This perspective has not been widely accepted at any time, but by some accounts, is experiencing a resurgence. New studies use this theory now to treat individuals diagnosed with autism spectrum disorders. Additionally, relational frame theory is growing from the behaviorist theory, which is important for acceptance and commitment therapy. Some empiricist theory accounts today use behaviorist models.

Other relevant theories about language development include Piaget's theory of cognitive development, which considers the development of language as a continuation of general cognitive development and Vygotsky's social theories that attribute the development of language to an individual's social interactions and growth.

Biological preconditions

Evolutionary biologists are skeptical of the claim that syntactic knowledge is transmitted in the human genome. However, many researchers claim that the ability to acquire such a complicated system is unique to the human species. Non-biologists also tend to believe that our ability to learn spoken language may have been developed through the evolutionary process and that the foundation for language may be passed down genetically. The ability to speak and understand human language requires speech production skills and abilities as well as multisensory integration of sensory processing abilities.

Scientists have conducted extensive research to see if other animal species are capable of learning a complex human language. Several studies have worked with great apes, owing to their close evolutionary relationship to humans. In the documentary Project Nim, for example, researcher Herbert S. Terrace conducted the study to nurture a young chimpanzee with intimate human interaction. The researchers trained the chimp American Sign Language and treated it like a human child. Finally, the chimp was able to learn over 114 signs to communicate his wants to the caregivers. Unlike humans, however, Nim was unable to make use of significant grammar or context. Other attempts to teach great apes language have met with varying degrees of success, and whether the communication the apes achieve can be equated to human language is controversial.

One hotly debated issue is whether the biological contribution includes capacities specific to language acquisition, often referred to as universal grammar. For fifty years, linguist Noam Chomsky has argued for the hypothesis that children have innate, language-specific abilities that facilitate and constrain language learning. In particular, he has proposed that humans are biologically prewired to learn language at a certain time and in a certain way, arguing that children are born with a language acquisition device (LAD). However, since he developed the minimalist program, his latest version of theory of syntactic structure, Chomsky has reduced the elements of universal grammar, which he believes are prewired in humans to just the principle of recursion, thus voiding most of the nativist endeavor.

Researchers who believe that grammar is learned rather than innate, have hypothesized that language learning results from general cognitive abilities and the interaction between learners and their human interactants. Based on studies of the developing visual system by Torsten Wiesel and David Hubel, it has been suggested that the environment guides the development of language networks in the brain by selecting the neurons and their synapses that are most active during the prolonged early development of humans in a socio-linguistic environment. According to this theory, the neural substrate for language results from a combination of the genetically determined complexity of the human brain and the 'functional validation of synapses' during the long period of postnatal maturation that is unique among primates. Further research has indicated the influence of the FOXP2 gene.

Stages

thumb|Relationship between interpersonal communication and the stages of development. The greatest development of language occurs in the stage of infancy. As the child matures, the rate of language development decreases.

0–1 years of age:

:An infant mainly uses non-verbal communication (mostly gestures) to communicate. For a newborn, crying is the only means of communication. Infants 1–5 months old have different tones of crying that indicate their emotions. Infants also begin laughing at this stage. At 6–7 months old, infants begin to respond to their own name, yell and squeal, and distinguish emotions based on the tone of voice of the parent. Between 7 and 10 months the infant starts putting words together, for example "mama" and "dada", but these words lack meaning and significance. Verbal communication begins at approximately 10–12 months, and the child starts to imitate any sounds they hear, for example animal sounds. The non-verbal communication of infants includes the use of gaze, head orientation and body positioning. Gestures are also widely used as an act of communication. All these stages can be delayed if the parents do not communicate with their infant on a daily basis.

:Nonverbal communication begins with the comprehension of parents and how they use it effectively in conversation. Infants are able to break down what adults and others are saying to them and use their comprehension of this communication to produce their own.

1–2 years of age:

:Verbal and nonverbal communication are both used at this stage of development. At 12 months, children start to repeat the words they hear. Adults, especially parents, are used as a point of reference for children in terms of the sound of words and what they mean in context of the conversation. Children learn much of their verbal communication through repetition and observing others. If parents do not speak to their children at this age it can become quite difficult for them to learn the essentials of conversation. The vocabulary of a 1–2-year-old should consist of 50 words and can be up to 500. Gestures that were used earlier on in development begin to be replaced by words and eventually are only used when needed. Verbal communication is chosen over nonverbal as development progresses.

2–3 years of age:

:Children aged 2–3 communicate best in a turn-taking style. This creates a conversational structure that makes it easier for verbal communication to develop. It also teaches patience, kindness, and respect as they learn from the direction of elders that one person should speak at a time. This creates interactional synchrony during their preverbal routines that shapes their interpersonal communication skills early on in their development. Children during this stage in their life also go through a recognition and continuity phase. Children start to see that shared awareness is a factor in communication along with their development of symbolic direction of language. This especially affects the relationship between the child and the caregiver; it is a crucial part of self-discovery for the child when they begin to take ownership over their own actions in a continuous manner. At the beginning of this stage toddlers tend to be missing function words and misunderstand how to use verb tenses. Over time they start including functional words, pronouns, and auxiliary verbs. This is the stage at which most children can pick up on emotional cues of the tone of adults' conversation. If negative feedback is distinguished by the child, this ends with fear and avoidance of the associated verbal and nonverbal cues. Toddlers develop the skills to listen and partially understand what another person is saying and can develop an appropriate response.

5–10 years of age:

:Much language development during this time period takes place in a school setting. At the beginning of the school age years, a child's vocabulary expands through exposure to reading, which also helps children to learn more difficult grammatical forms, including plurals and pronouns. They also begin to develop metalinguistic awareness which allows them to reflect and more clearly understand the language they use. They therefore start to understand jokes and riddles. Reading is a gateway for learning new vernacular and having confidence in complex word choices while talking with adults. This is an important developmental stage socially and physiologically for the child. School-aged children can easily be influenced through communication and gestures. They often use colloquial speech (slang), however, which can increase confusion and misunderstandings. performed a study in 1986 by having mothers read aloud during the last few weeks of pregnancy. When the infants were born, they were then tested. They were read aloud a story while sucking on a pacifier; the story was either the story read by the mother when the infant was in utero or a new story. The pacifier used was able to determine the rate of sucking that the infant was performing. When the story that the mother had read before was heard, the sucking of the pacifier was modified. This did not occur during the story that the infant had not heard before. The results for this experiment had shown that the infants were able to recognize what they had heard in utero, providing insight that language development had been occurring in the last six weeks of pregnancy.

Throughout the first year of life, infants are unable to communicate with language. Instead, infants communicate with gestures. This phenomenon is known as prelinguistic gestures, which are nonverbal ways that infants communicate that also had a plan backed with the gesture. Examples of these could be pointing at an object, tugging on the shirt of a parent to get the parent's attention, etc. Harding, 1983, devised the major criteria that come along with the behavior of prelinguistic gestures and their intent to communicate. There are three major criteria that go along with a prelinguistic gesture: waiting, persistence, and ultimately, development of alternative plans. This process usually occurs around 8 months of age, where an appropriate scenario may be of a child tugging on the shirt of a parent to wait for the attention of the parent who would then notice the infant, which causes the infant to point to something they desire. This would describe the first two criteria. The development of alternative plans may arise if the parent does not acknowledge what the infant wants, the infant may entertain itself to satisfy the previous desire. The way the parent responds to their child in this situation of "needing" and "wanting" will also result in the kind of attachment style their child will have.

When children reach about 15–18 months of age, language acquisition flourishes. There is a surge in word production resulting from the growth of the cortex. Infants begin to learn the words that form a sentence and within the sentence, the word endings can be interpreted. Elissa Newport and colleagues (1999) found that humans learn first about the sounds of a language, and then move on to how to speak the language. This shows how infants learn the end of a word and know that a new word is being spoken. From this step, infants are then able to determine the structure of a language and word.

It appears that during the early years of language development females exhibit an advantage over males of the same age. When infants between the age of 16 and 22 months were observed interacting with their mothers, a female advantage was obvious. The females in this age range showed more spontaneous speech production than the males and this finding was not due to mothers speaking more with daughters than sons. In addition, boys between 2 and 6 years as a group did not show higher performance in language development over their girl counterparts on experimental assessments. In studies using adult populations, 18 and over, it seems that the female advantage may be task dependent. Depending on the task provided, a female advantage may or may not be present. Similarly, one study found that out of the 5.5% of American children with language impairments, 7.2% are male, and 3.8% are female. There are many different suggested explanations for this gender gap in language impairment prevalence.

Lateralization effect on language

It is currently believed that in regards to brain lateralization males are left-lateralized, while females are bilateralized. Studies on patients with unilateral lesions have provided evidence that females are in fact more bilateralized with their verbal abilities. It seems that when a female has experienced a lesion to the left hemisphere, she is better able to compensate for this damage than a male can. If a male has a lesion in the left hemisphere, his verbal abilities are greatly impaired in comparison to a control male of the same age without that damage. However, these results may also be task-dependent as well as time-dependent.

Fine motor development rate

Shriberg, Tomblin, and McSweeny (1999) suggest that the fine motor skills necessary for correct speech may develop more slowly in males. This could explain why some of the language impairments in young males seem to spontaneously improve over time.

Over-diagnosis

It is also suggested that the gender gap in language impairment prevalence could also be explained by the clinical over diagnosis of males. Males tend to be clinically over diagnosed with a variety of disorders. In the research that has been conducted, focus has generally centred on the development of written and spoken language and their connection. Spoken and written skills could be considered linked. Researchers believe that children's spoken language influences their written language. When a child learns to write they need to master letter formation, spelling, punctuation and they also have to gain an understanding of the structure and the organisational patterns involved in written language.

Kroll's theory is one of the most significant on children's writing development. He proposed that children's writing development is split into four phases. Kroll explicitly states that these phases are 'artificial' in the sense that the boundaries between the phases are imprecise and he recognises that each child is different, thus their development is unique. In this phase, the child learns that writing is generally considered more formal than spoken language, which is thought to be casual and conversational. Here, it is believed that children begin to understand that writing serves a purpose. Perera is also aware that it is hard to assign chronological ages to each phase of writing development, because each child is an individual, and also the phases are 'artificial'.

Other than Kroll's theory, there are four principles on early patterns in writing development discussed by Marie Clay in her book What Did I Write?. The four principles are recurring principle, the generative principle, the sign principle, and the inventory principle. The recurring principle involves patterns and shapes in English writing that develop throughout writing development. The generative principle incorporates the idea that a writer can create new meanings by organizing units of writing and letters of the alphabet. The sign principle is understanding that the word print also involves paper arrangement and word boundaries. And lastly, the inventory principle is the fact that children have the urge to list and name items that they are familiar with, and because of this they can practice their own writing skills.

More recent research has also explored writing development. Myhill concentrated on the development of written language skills in adolescents aged 13 to 15. Myhill discovered that the more mature writer was aware of the shaping of text, and used non-finite clauses, which mirrored Perera's results (1984). Environmental influences on language development are explored in the tradition of social interactionist theory by such researchers as Jerome Bruner, Alison Gopnik, Andrew Meltzoff, Anat Ninio, Roy Pea, Catherine Snow, Ernest Moerk and Michael Tomasello. Jerome Bruner who laid the foundations of this approach in the 1970s, emphasized that adult "scaffolding" of the child's attempts to master linguistic communication is an important factor in the developmental process.

One component of the young child's linguistic environment is child-directed speech (also known as baby talk or motherese), which is language spoken in a higher pitch than normal with simple words and sentences. Although the importance of its role in developing language has been debated, many linguists think that it may aid in capturing the infant's attention and maintaining communication. When children begin to communicate with adults, this motherese speech allows the child the ability to discern the patterns in language and to experiment with language.

Throughout existing research, it is concluded that children exposed to extensive vocabulary and complex grammatical structures more quickly develop language and also have a more accurate syntax than children raised in environments without complex grammar exposed to them. This is especially true for children with autism, who may have more difficulty acquiring language, that "rich and responsive" language from an adult gives much more support to the development of language. With motherese, the mother talks to the child and responds back to the child, whether it be a babble the child made or a short sentence. While doing this, the adult prompts the child to continue communicating, which may help a child develop language sooner than children raised in environments where communication is not fostered.

Child-directed speech concentrates on small core vocabulary, here and now topics, exaggerated facial expressions and gestures, frequent questioning, para-linguistic changes, and verbal rituals. An infant is least likely to produce vocalizations when changed, fed, or rocked. The infant is more likely to produce vocalizations in response to a nonverbal behavior such as touching or smiling.

Child-directed speech also catches the child's attention, and in situations where words for new objects are being expressed to the child, this form of speech may help the child recognize the speech cues and the new information provided.

Expanding is restating, in a linguistically sophisticated form, what a child has said. For example, a child may say "car move road" and the parent may respond "A car drives on the road."

Cultural and socioeconomic effects

While most children throughout the world develop language at similar rates and without difficulty, cultural and socioeconomic differences have been shown to influence development. An example of cultural differences in language development can be seen when comparing the interactions of mothers in the United States with their infants with mothers in Japan. Mothers in the United States use more questions, are more information-oriented, and use more grammatically correct utterances with their 3-month-olds. Mothers in Japan, on the other hand, use more physical contact with their infants, and more emotion-oriented, nonsense, and environmental sounds, as well as baby talk, with their infants. These differences in interaction techniques reflect differences in "each society's assumptions about infants and adult-to-adult cultural styles of talking."

It is crucial that children are allowed to socially interact with other people who can vocalize and respond to questions. For language acquisition to develop successfully, children must be in an environment that allows them to communicate socially in that language. Children who have learnt sound, meaning and grammatical system of language that can produce clear sentence may still not have the ability to use language effectively in various social circumstance. Social interaction is the footing stone of language.

There are a few different theories as to why and how children develop language. One popular, yet heavily debated explanation is that language is acquired through imitation. This theory has been challenged by Lester Butler, who argues that children do not use the grammar that an adult would use. Furthermore, "children's language is highly resistant to alteration by adult intervention", meaning that children do not use the corrections given to them by an adult. R.L Trask also argues in his book Language: The Basics that deaf children acquire, develop and learn sign language in the same way hearing children do, so if a deaf child's parents are fluent sign speakers, and communicate with the baby through sign language, the baby will learn fluent sign language. And if a child's parents aren't fluent, the child will still learn to speak fluent sign language. Trask's theory therefore is that children learn language by acquiring and experimenting with grammatical patterns, the statistical language acquisition theory.

The two most accepted theories in language development are psychological and functional.

Psychological explanations focus on the mental processes involved in childhood language learning. Functional explanations look at the social processes involved in learning the first language.

Aspects

Phonology involves the rules about the structure and sequence of speech sounds.
Semantics consists of vocabulary and how concepts are expressed through words.
Grammar involves two parts.
The first, syntax, is the rules in which words are arranged into sentences.
The second, morphology, is the use of grammatical markers (indicating tense, active or passive voice etc.).
Pragmatics involves the rules for appropriate and effective communication. Pragmatics involves three skills:
using language for greeting, demanding etc.,
changing language for talking differently depending on who it is you are talking to;
following rules such as turn taking, staying on topic.

Each component has its own appropriate developmental periods.

Phonological development

Babies can recognize their mother's voice from as early as few weeks old. It seems like they have a unique system that is designed to recognize speech sound. Furthermore, they can differentiate between certain speech sounds. A significant first milestone in phonetic development is the babbling stage (around the age of six months). This is the baby's way of practicing his control over that apparatus. Babbling is independent from the language. Deaf children for instance, babble the same way as hearing ones.

As the baby grows older, the babbling increases in frequency and starts to sound more like words (around the age of twelve months). Although every child is an individual with different pace of mastering speech, there is a tendency to an order of which speech sounds are mastered:

Vowels before consonants
Stop sounds before any other consonant sounds (for example: 'p','t','b')
Place of articulation – labials, alveolar, velars, alveopalatals, and interdentals in that order by the age of 4. That means that there is some order to the development of the physical system in young children.

Early phonetic processes

As the children's ability to produce sound develops, their ability to perceive the phonetic contrast of their language develops. The better they get in mastering the sound, the more sensitive they become to the changes in those sounds in their language once they get exposed to it. They learn to isolate individual phonemes while speaking which also serves as the basis of reading.

Some processes that occur in early age:

Syllable deletion – stressed syllables are emphasis that may be given to certain syllables in a word. They are more likely to be retained in children's pronunciation than unstressed syllables (less emphasis on the sound) because they are more salient to children in an early language acquisition process. So children may say helikat instead of helicopter or fowe instead of telephone. That way, they don't pronounce the more emphasized sound in the word.
Syllable simplification – another process that happens in order to simplify syllable structure, children delete certain sounds systematically. For example, children might say 'tap' instead of "stop" and completely drop the 's' sound in that word. That is a common process in children's speech development.
Substitution – systematic replacement of one sound by an alternative, easier one to articulate (substitution process – stopping, fronting, gliding). It means that the young toddler may use sounds that are easier to produce instead of the proper sound in a word. We may see that the child replace the 'r' sound with 'l' or 'w', the 'n' with 'd' and so on.
Assimilation – modification of segments of the word influenced by neighboring sounds, due to ease of articulation. In order for the young speaker to produce sounds easier, he or she may replace the sound in a specific word to a different one, which is somewhat similar. For example, the word "pig" may sound as "big" – 'p' and 'b' are close in their sound. (Lightbown, Spada, Ranta & Rand, 2006).

From shortly after birth to around one year, the baby starts to make speech sounds.

At around two months, the baby engages in cooing, which mostly consists of vowel sounds. At around four to six months, cooing turns into babbling, which is the repetitive consonant-vowel combinations. Babies understand more than they are able to say. In this 0–8 months range, the child is engaged in vocal play of vegetative sounds, laughing, and cooing.

Once the child hits the 8–12-month, range the child engages in canonical babbling, i.e. dada as well as variegated babbling. This jargon babbling with intonational contours the language being learned.

From 12–24 months, babies can recognize the correct pronunciation of familiar words. Babies also use phonological strategies to simplify word pronunciation. Some strategies include repeating the first consonant-vowel in a multisyllable word ('TV' → 'didi') or deleting unstressed syllables in a multisyllable word ('banana' → 'nana'). Within this first year, two-word utterances and two syllable words emerge. This period is often called the holophrastic stage of development, because one word conveys as much meaning as an entire phrase. For instance, the simple word "milk" can imply that the child is requesting milk, noting spilled milk, sees a cat drinking milk, etc. One study found that children at this age were capable of comprehending 2-word sentences, producing 2–3-word sentences, and naming basic colors.

By 24–30 months awareness of rhyme emerges as well as rising intonation. One study concludes that children between the ages of 24 and 30 months typically can produce 3–4-word sentence, create a story when prompted by pictures, and at least 50% of their speech is intelligible. At this age, children have a considerable experience with language and are able to form simple sentences that are 3 words in length.

Semantic development

The average child masters about fifty words by the age of eighteen months. These might include words such as, milk, water, juice and apple (noun-like words). Afterwards they acquire 12 to 16 words a day. By the age of six, they master about 13 to 14 thousand words.

The most frequent words include adjective-like expressions for displeasure and rejection such as 'no'. They also include social interaction words, such as "please" and "bye".

There are three stages for learning the meaning of new words:

Whole object assumption: A new word refers to a whole object. For example, when an eighteen-months old child sees a sheep and his mother points at it and says the word 'sheep', the child infers that the word 'sheep' describes the whole animal and not parts of it (such as color, shape, etc.).
Type assumption: A new word refers to a type of thing, not just to a particular thing. For example, when the child hears the word 'sheep' he infers that it is used for the animal type and not only for that particular sheep that he saw.
Basic level assumption: A new word refers to objects that are alike in basic ways (appearance, behavior, etc.).

In other words, when the child hears the word "sheep" he overgeneralizes it to other animals that look like sheep by the external appearance, such as white, wooly and four-legged animal.

Contextual clues are a major factor in the child's vocabulary development.

The child uses contextual clues to draw inferences about the category and meaning of new words. By doing so, the child distinguishes between names and ordinary nouns.

For example, when an object is presented to the child with the determiner "a" (a cat, a dog, a bottle) he perceives it as an ordinary noun.

However, when the child hears a noun without the determiner, he perceives it as a name, for instance "this is Mary".

Children usually make correct meaning associations with the words that the adults say. However, sometimes they make semantic errors.

There are a few types of semantic errors:

Overextension: When a child says or hears a word, they might associate what they see or hear as more generalized concept than the real meaning of the word. For example, if they say "cat", they might overextend it to other animals with same features.

Underextension: It involves the use of lexical items in an overly restrictive fashion. In other words, the child focuses on core members of a certain category. For example: 'cat' may only refer to the family cat and no other cat, or 'dog' may refer to certain kinds of dogs that the child is exposed to.

Verb meaning: when a pre-school child hears the verb 'fill', he understands it as the action 'pour' rather than the result, which is 'make full'.

Dimensional terms: the first dimensional adjectives acquired are big and small because they belong to the size category. The size category is the most general one. Later children acquire the single dimension adjectives, such as, tall-short, long-short, high-low. Eventually they acquire the adjectives that describe the secondary dimension, such as thick-thin, wide-narrow and deep-shallow.

From birth to one year, comprehension (the language we understand) develops before production (the language we use). There is about a 5-month lag in between the two. Babies have an innate preference to listen to their mother's voice. Babies can recognize familiar words and use preverbal gestures.

Within the first 12–18 months semantic roles are expressed in one word speech including agent, object, location, possession, nonexistence and denial. Words are understood outside of routine games but the child still needs contextual support for lexical comprehension.

18–24 months Prevalent relations are expressed such as agent-action, agent-object, action-location.

Syntactic development and morphological development

Syntactic development involves the ways that various morphemes are ordered or combined in sentences. Morphemes, which are basic units of meaning in language, get added as children learn to produce simple sentences and become more precise speakers. Morphemes can be whole words (like "happy") or parts of words that change meaning of words ("un"happy). Brown

Stage I: From 15–30 months, children start using telegraphic speech, which are two-word combinations, for example 'wet diaper'. Brown (1973) observed that 75% of children's two-word utterances could be summarized in the existence of 11 semantic relations: on the basis of their sensitivity to social contingency, which can elicit social responses in the babies from very early on. For example, most acquire early sensitivity to the prosodic patterns of social rituals such as peek-a-boo.

By age 0.5–1 years, infants understand that speech sounds can express intentions (such as requests) as opposed to coughs. They also recognize that variability of exchanged signal sequences and turn-taking are prerequisites of communicative information transfer.
By age 1–2 years, they can engage in turn-taking exchanges and understand that turn-taking interactions of observed others can convey goal-relevant, communicative information.
By age 3–5 years, children can master illocutionary intent, knowing what you meant to say even though you might not have said it and turnabout, which is turning the conversation over to another person.
By age 6–10 years, shading occurs, which is changing the conversation topic gradually. Children are able to communicate effectively in demanding settings, such as on the telephone.

Effect of bilingualism

There is a large debate regarding whether or not bilingualism is truly beneficial to children. Parents of children often view learning a second language throughout elementary and high school education beneficial to the child. Another perspective dictates that the second language just confuses the child and prevents them from mastering their primary language. Studies have shown that American bilingual children have greater cognitive flexibility, better perceptual skills and tend to be more divergent thinkers than monolingual children between the ages of five and ten. In addition, bilingual children have a better understanding of universal language concepts, such as grammar, because these concepts are applied in multiple languages. However, studies comparing Swedish-Finnish bilingual children and Swedish monolingual children between the ages of five and seven have also shown that the bilingual children have a smaller vocabulary than monolingual children. In another study throughout America, elementary school English-monolingual children performed better in mathematics and reading activities than their non-English-dominant bilingual and non-English monolingual peers from kindergarten to grade five. Learning two languages simultaneously can be beneficial or a hindrance to a child's language and intellectual development. Further research is necessary to continue to shed light on this debate.

In addition to the study of bilingualism in children, similar research is being conducted in adults. Research findings show that although bilingual benefits are muted in middle adulthood, The increased attentional control, inhibition, and conflict resolution developed from bilingualism may be accountable for the later onset of dementia. A subtopic of bilingualism in the literature is nonstandard varieties of English. While bilingualism and nonstandard varieties of English cannot be considered a true language impairment, they are misrepresented in the population of those receiving language interventions.

Language disorders

A language disorder is the impaired comprehension and or use of a spoken, written, or other symbol system. A disorder may involve problems in the following areas:

The form of language i.e. phonology, morphology, or syntax
The content i.e. semantics
The function of language in communication i.e. pragmatics

Olswang and colleagues have identified a series of behaviors in children in the 18–36-month range that are predictors for the need of language intervention.

These predictors include:

A smaller than average vocabulary
A language comprehension delay of 6 months or a comprehension deficit with a large comprehension production gap
Phonological problems such as restricted babbling or limited vocalizations
Few spontaneous vocal imitations and reliance on direct modeling in imitation tasks
Little combinatorial or symbolic play
Few communicative or symbolic gestures
Behavior problems