Cognitive development is a field of study in neuroscience and psychology focusing on a child's development in terms of information processing, conceptual resources, perceptual skill, language learning, and other aspects of brain development and cognitive psychology compared to an adult's point of view. In other words, cognitive development is the emergence of the ability to think and understand.[1] A large portion of research has gone into understanding how a child imagines the world. Jean Piaget was a major force in the establishment of this field, forming his "theory of cognitive development". Piaget proposed four stages of cognitive development: the sensorimotor, preoperational, concrete operational and formal operational period.[2] Many of his theoretical claims have since fallen out of favor. However, his description of the more prominent changes in cognition with age (e.g., that it moves from being dependent on actions and perception in infancy to an understanding of the more observable aspects of reality in childhood to capturing the underlying abstract rules and principles in adolescence) is generally still accepted today. Perhaps equally importantly, Piaget identified and described many cognitive changes that must be explained, such as object permanence in infancy and the understanding of logical relations and cause-effect reasoning in school age children. The many phenomena he described still attract the interest of many current researchers.

In recent years, however alternative models have been advanced, including information-processing theory, neo-Piagetian theories of cognitive development, which aim to integrate Piaget's ideas with more recent models and concepts in developmental and cognitive science, theoretical cognitive neuroscience, and social-constructivist approaches.

A major controversy in cognitive development has been "nature and nurture", that is, the question if cognitive development is mainly determined by an individual's innate qualities ("nature"), or by their personal experiences ("nurture"). However, it is now recognized by most experts that this is a false dichotomy: there is overwhelming evidence from biological and behavioral

sciences that from the earliest points in development, gene activity interacts with events and experiences in the environment.[3]

Historical Origins: Piaget’s theory of cognitive development[edit]

Main article: Piaget's theory of cognitive development

Jean Piaget (1896-1980) believed that people move through stages of development that allow them to think in new, more complex ways.

Sensorimotor stage[edit]

The first stage in Piaget’s Stages of Cognitive Development is the sensorimotor stage. This stage lasts from birth to two years old. During this stage, behaviors lack a sense of thought and logic. Behaviors gradually move from acting upon inherited reflexes to interacting with the environment with a goal in mind and being able to represent the external world at the end.

The sensorimotor stage has been broken down into six sub stages that explain the gradual development of infants at this age.

Birth to one month

Each child is born with inherited reflexes that they use to gain knowledge and understanding about their environment. Examples of these reflexes include grasping and sucking.[4]

1–4 months

Children repeat behaviors that happen unexpectedly because of their reflexes.

For example, a child’s finger comes in contact with the mouth and the child starts sucking on it. If the sensation is pleasurable to the child, then the child will attempt to recreate the behavior.[4] Infants use their initial reflexes (grasping and sucking) to explore their environment and create schemes. Schemes are groups of similar actions or thoughts that are used repeatedly in response to the environment.[5] Once a child begins to create schemes they use accommodation and assimilation to become progressively adapted to the world.[6] Assimilation is

when a child responds to a new event in a way that is consistent with an existing schema. For example, an infant may assimilate a new teddy bear into their putting things in their mouth scheme and use their reflexes to make the teddy bear go into their mouth.[5] Accommodation is when a child either modifies an existing scheme or forms an entirely new schema to deal with a new object or event. For example, an infant may have to open his or her mouth wider than usual to accommodate the teddy bear's paw.[5]

5–8 months

Child has an experience with an external stimulus that they find pleasurable, so they try to recreate that experience. For example, a child accidentally hits the mobile above the crib and likes to watch it spin. When it stops the child begins to grab at the object to make it spin again.In this stage habits are formed from general schemes that the infant has created but there is not yet, from the child’s point of view, any differentiation between means and ends.[7] Children cannot also focus on multiple tasks at once, and only focus on the task at hand.[5] The child may create a habit of spinning the mobile in its crib, but they are still trying to find out methods to reach the mobile in order to get it to spin in the way that they find pleasurable. Once there is another distraction (say the parent walks in the room) the baby will no longer focus on the mobile. Toys should be given to infants that respond to a child’s actions to help foster their investigative instincts.[8] For example, a toy plays a song when you push one button, and then a picture pops up if you push another button.

8–12 months

Behaviors will be displayed for a reason rather than by chance. They begin to understand that one action can cause a reaction.[4] They also begin to understand object permanence, which is the realization that objects continue to exist when removed form view. For example: The baby wants a rattle but the blanket is in the way. The baby moves the blanket to get the rattle. Now that the infant can understand that they object still exists, they can differentiate between the object, and the experience of the object. According to psychologist David Elkind, “An internal representation of the absent object is the earliest

manifestation of the symbolic function which develops gradually during the second year of life whose activities dominate the next stage of mental growth." [9]

12–18 months

Actions occur deliberately with some variation.For example a baby drums on a pot with a wooden spoon, then drums on the floor, then on the table.[4]

18 - 24 months

Children begin to build mental symbols and start to participate in pretend play. For example, a child is mixing ingredients together but doesn't have a spoon so they pretend to use one or use another object the replace the spoon [4]Symbolic thought is a representation of objects and events as mental entities or symbols which helps foster cognitive development and the formation of imagination.[10] According to Piaget, the infant begins to act upon intelligence rather than habit at this point. The end product is established after the infant has pursued for the appropriate means. The means are formed from the schemes that are known by the child.[7] The child is starting to learn how to use what it has learned in the first two years to develop and further explore their environment.

These six sub-stages represent the approximate growth a child undergoes during Piaget’s sensorimotor stage from birth to age 2. Once the child gains the ability to mentally represent reality, the child begins the transition to the preoperational stage of development.[11]

Preoperational stage[edit]

Lasts from 2 years of age until 6 or 7. It can be characterized in two somewhat different ways. In his early work, before he had developed his structuralist theory of cognition, Piaget described the child’s thought during this period as being governed by principles such as egocentrism, animism and other similar constructs. Egocentrism is when a child can only see a certain situation his or her own way. One can not comprehend that other people have other views and perceptions of scenarios. Animism is when an individual gives a lifeless object

human like qualities. An individual usually believes that this object has human emotions, thoughts and intentions. Once he had proposed his structuralist theory, Piaget characterized the preoperational child as lacking the cognitive structures possessed by the concrete operational child. The absence of these structures explains, in part, the behaviors Piaget had previously described as egocentric and animistic, for example an inability to comprehend that another individual may have different emotional responses to similar experiences.[11][12]

Concrete operational stage[edit]

Lasts from 6 or 7 years until about 12 or 13. During this stage the child’s cognitive structures can be characterized by group therapy. Piaget argues that the same general principles can be discerned in a wide range of behaviors. One of the best-known achievements of this stage is that of conservation. In a typical conservation experiment a child is asked to judge whether or not two quantities are the same – such as two equal quantities of liquid in a short and tall glass. A preoperational child will typically judge the taller, thinner glass to contain more, while a concrete operational child will judge the amounts still to be the same. The ability to reason in this way reflects the development of a principle of conservation.[11]

Criticism[edit]

Many of his claims have fallen out of favor. For example, he claimed that young children cannot conserve number. However, further experiments show that children did not really understand what was being asked of them. When the experiment is done with candies, and the children are asked which set they want rather than tell an adult which is more, they show no confusion about which group has more items.[citation needed]

Other theoretical perspectives on cognitive development[edit]

Speculated core systems of cognition[edit]

Empiricists study how these skills may be learned in such a short time. The debate is over whether these systems are learned by general-purpose learning devices, or domain-specific cognition. Moreover, many modern cognitive developmental psychologists, recognizing that the term "innate" does not square with modern knowledge about epigenesis, neurobiological development, or learning, favor a non-nativist framework. Researchers who discuss "core systems" often speculate about differences in thinking and learning between proposed domains. Researchers who posit a set of so-called "core domains" suggest that children are innate sensitivity to specific kinds of patterns of information. Those commonly cited include:

Number

Infants appear to have two systems for dealing with numbers. One deals with small numbers, often called subitizing. Another deals with larger numbers in an approximate fashion.[13]

Space

Very young children appear to have some skill in navigation. This basic ability to infer the direction and distance of unseen locations develops in ways that are not entirely clear. However, there is some evidence that it involves the development of complex language skills between 3 and 5 years.[14] Also, there is evidence that this skill depends importantly on visual experience, because congenitally blind individuals have been found to have impaired abilities to infer new paths between familiar locations.

Visual perception

One of the original nativist versus empiricist debates was over depth perception. There is some evidence that children less than 72 hours old can perceive such complex things as biological motion.[15] However, it is unclear how visual experience in the first few days contributes to this perception. There are far more elaborate aspects of visual perception that develop during infancy and beyond. [elaboration of this section is forthcoming!]

Essentialism

Young children seem to be predisposed to think of biological entities (e.g., animals and plants) in an essentialistic way.[16] This means that they expect such entities (as opposed to, e.g., artifacts) to have many traits such as internal properties that are caused by some "essence" (such as, in our modern Western conceptual framework, the genome).

Language acquisition

A major, well-studied process and consequence of cognitive development is language acquisition. The traditional view was that this is the result of deterministic, human-specific genetic structures and processes. Other traditions, however, have emphasized the role of social experience in language learning. However, the relation of gene activity, experience, and language development is now recognized as incredibly complex and difficult to specify. Language development is sometimes separated into learning of phonology, morphology, syntax, semantics, and discourse or pragmatics. However, all of these aspects of language knowledge—which were originally posited by the linguist Noam Chomsky to be autonomous or separate—are now recognized to interact in complex ways.

Whorf's hypothesis[edit]

Main article: Linguistic relativity

Benjamin Whorf (1897 – 1941), while working as a student of Edward Sapir, posited that a person's thinking depends on the structure and content of their social group's language. In other words, it is the belief that language determines our thoughts and perceptions. For example, it used to be thought that Greeks, who wrote left to right, thought differently than Egyptians since the Egyptians wrote right to left. Whorf’s theory was so strict that he believed if a word is absent in a language, then the individual is unaware of the object’s existence.[17] This theory was played out in George Orwell’s book, Animal Farm; the pig leaders slowly eliminated words from the citizen’s vocabulary so that they were incapable of realizing what they were missing.[18] The Whorfian hypothesis failed to

recognize that people can still be aware of the concept or item, even though they lack efficient coding to quickly identify the target information.[17]

Quine's bootstrapping hypothesis[edit]

Willard Van Orman Quine (1908-2000) suggested that there are innate conceptual biases that determine the language meaning that we acquire, and the concepts and beliefs that we acquire, as we develop. Quine's theory relates to other nativist philosophical traditions, such as the European rationalist philosophers. A relevant figure in this nativist tradition for cognitive developmental theory is Immanuel Kant.

Neuroscience[edit]

During development, especially the first few years of life, children show interesting patterns of neural development and a high degree of neuroplasticity. The relation of brain development and cognitive development is extremely complex and, since the 1990s, has been a growing area of research.

Cultural influences[edit]

From cultural psychologists’ view, minds and culture shape each other. In other words, culture can influence brain structures which then influence our interpretation of the culture. These examples reveal cultural variations in neural responses:

Figure-Line Task (Hedden et al., 2008)

Behavioral research has shown that one’s strength in independent or interdependent tasks differ based on their cultural context. In general, East Asian cultures are more interdependent whereas Western cultures are more independent.[clarification needed] Hedden et al. assessed functional magnetic resonance imaging (fMRI) responses of East Asians and Americans while they performed independent (absolute) or interdependent (relative) tasks. The study showed that participants used regions of the brain associated with attentional control when they had to perform culturally incongruent tasks. In other words, different neural paths used for the same task were different for Americans and East Asians (Hedden et al., 2008).[19]

Kobayashi et al., 2007

Kobayashi et al. compared American-English monolingual and Japanese-English bilingual children’s brain responses in understanding others’ intentions through false-belief story and cartoon tasks. They found universal activation of the region bilateral ventromedial prefrontal cortex in Theory of Mind tasks. However, American children showed greater activity in the left inferior frontal gyrus during the tasks whereas Japanese children had greater activity in right inferior frontal gyrus during the Japanese Theory of Mind tasks. In conclusion, these examples suggest that the brain’s neural activities are not universal but are culture dependent

Language development is a process starting early in human life. Infants start without language, yet by 4 months of age, babies can discriminate 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.

Usually, productive language is considered to begin with a stage of preverbal 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 which they had already expressed by preverbal means.[citation needed]

]

Main article: Language acquisition

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.[citation needed] The method in which we develop language skills is universal however, the major debate is how the rules of syntax are acquired.[citation needed] There are two major approaches to 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.[citation needed]

The nativist theory, proposed by Noam Chomsky, argues that language is a unique human accomplishment.[citation needed] 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 construct novel sentences using learned vocabulary. 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.[citation needed] He argues that linguistic input from the environment is limited and full of errors. Therefore, nativists assume that it is impossible for children to learn linguistic information solely from their environment.[citation needed] However, because children possess this LAD, they are in fact, able to learn language despite incomplete information from their environment. 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.[citation needed]

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 which evolved specifically for language, empiricists believe that general brain processes are sufficient enough for language acquisition. During this process, it is necessary for the child to be actively engaged with their environment. In order 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).[citation needed] 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.[citation needed]

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.[1]

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.[2] Some empiricist theory accounts today use behaviorist models.[3]

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[4] and Vygotsky's social theories that attribute the development of language to an individual's social interactions and growth.[5]

Biological preconditions[edit]

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.[citation needed]

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.[citation needed] 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).[6] However, since he developed the Minimalist Program, his latest version of theory of syntactic structure, Chomsky has reduced the elements of universal grammar which are in his opinion to be prewired in humans to just the principle of recursion, thus voiding most of the nativist endeavor.[7]

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. It has also recently been suggested that the relatively slow development of the prefrontal cortex in humans may be one reason that humans are able to learn language, whereas other species are not.[8][9] Further research has indicated the influence of the FOXP2 gene.[10]

Gender Differences[edit]

Children versus adults[edit]

It seems as if during the early years of language development females exhibit an advantage over males of the same age. When infants between the age of 16 to 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.[11] 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.[12]

Lateralization effect on language[edit]

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.[13] However, these results may also be task dependent as well as time dependent.[14]

Environmental Influences[edit]

The environment a child develops in has influences on language development. The environment provides language input for the child to process. Speech by adults to children help provide the child with correct language usage repetitively.[citation needed] 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.[citation needed]

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.[15] 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 research done, 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. 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 is prompting the child to continue communicating which may help a child develop language sooner than children raised in environments where communication is not fostered.[citation needed]

Child-directed speech will concentrate on small core vocabulary, here and now topics, exaggerated facial expressions and gestures, frequent questioning, paralinguistic changes, and verbal rituals.[16] An infant is least likely to produce vocalizations when changed, fed, or rocked. The infant will more likely produce vocalizations when a nonverbal behavior such as touching or smiling is directed at the infant.[citation needed]

Child-directed speech will also catch 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. Data shows that children raised in highly verbal families had higher language scores than those children raised in low verbal families. Continuously hearing complicated sentences throughout language development increases the child's ability to understand these sentences and then to use complicated sentences as they develop. Studies have shown that students enrolled in high language

classrooms have two times the growth in complex sentences usage than students in classrooms where teachers do not frequently use complex sentences.[citation needed]

Adults use strategies other than child-directed speech like recasting, expanding, and labeling: Recasting is rephrasing something the child has said, perhaps turning it into a question or restating the child's immature utterance in the form of a fully grammatical sentence. For example, a child saying "cookie now" a parent may respond with "Would you like a cookie now?"[citation needed] 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."[citation needed] Labeling is identifying the names of objects[6] If a child points to an object such as a couch the mother may say "couch" in response. Labeling can also be characterized as referencing.[16]

Some language development experts have characterized child directed speech in stages. Primarily, the parents will use repetition and also variation to maintain the infant's attention. Secondly, the parent will simplify speech to help in language learning. Third, any modifications in speech will maintain the responsiveness of the child. These modifications develop into a conversation that provides context for the development.[16]

Cultural and Socioeconomic Effects on Language Development[edit]

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.[citation needed] Mothers in the United States use more questions, are more information oriented, and use

more grammatically correct utterances with their 3-month-olds.[citation needed] 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."[16]

Specifically in North American culture, maternal race, education, and socioeconomic class influence parent-child interactions in the early linguistic environment.[citation needed] When speaking to their infants, mothers from middle class "incorporate language goals more frequently in their play with their infants," and in turn, their infants produce twice as many vocalizations as lower class infants.[16] Mothers from higher social classes who are better educated also tend to be more verbal, and have more time to spend engaging with their infants in language. Additionally, lower class infants may receive more language input from their siblings and peers than from their mothers.[citation needed]

Social preconditions[edit]

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.[citation needed]

There are a few different theories as to why and how children develop language. The most popular—and yet heavily debated—explanation is that language is acquired through imitation.[citation needed] The two most accepted theories in language development are psychological and functional.[citation needed] 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.

There are four main components of language:

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[edit]

From shortly after birth to around one year, the baby starts to make speech sounds. At around two months, the baby will engage in cooing, which mostly consists of vowel sounds. At around four 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.[citation needed]

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.[citation needed]

From 12–24 months, babies can recognize the correct pronunciation of familiar words. Babies will 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.[17]

By 24–30 months awareness of rhyme emerges as well as rising intonation.[citation needed]

By 36–60 months, phonological awareness continues to improve as well as pronunciation.[citation needed]

By 6–10 years, children can master syllable stress patterns which helps distinguish slight differences between similar words.[citation needed]

Semantic development[edit]

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.[citation needed]

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]

18–24 months Prevalent relations are expressed such as agent-action, agent-object, action-location[18] Also, there is a vocabulary spurt between 18–24 months, which includes fast mapping. Fast mapping is the babies' ability to learn a lot of new things quickly. The majority of the babies' new vocabulary consists of object words (nouns) and action words (verbs).

30–36 months The child is able to use and understand why question and basic spatial terms such as in, on or under.[citation needed]

36–42 months There is an understanding of basic color words and kinship terms. Also, the child has an understanding of the semantic relationship between adjacent and conjoined sentences, including casual and contrastive.[citation needed]

42–48 months When and how questions are comprehended as well as basic shape words such as circle, square and triangle.[citation needed]

48–60 months Knowledge of letter names and sounds emerges, as well as numbers.

By 3–5 years, children usually have difficulty using words correctly. Children experience many problems such as underextensions, taking a general word and applying it specifically (for example, 'blankie') and overextensions, taking a specific word and applying it too generally (example, 'car' for 'van'). However, children coin words to fill in for words not yet learned (for example, someone is a cooker rather than a chef because a child will not know what a chef is). Children can also understand metaphors.[citation needed]

From 6–10 years, children can understand meanings of words based on their definitions. They also are able to appreciate the multiple meanings of words and use words precisely through metaphors and puns. Fast mapping continues.[citation needed] Within these years, children are now able to acquire new information from written texts and can explain relationships between multiple meaning words. Common idioms are also understood.[citation needed]

Grammatical development[edit]

From 1–2 years, children start using telegraphic speech, which are two word combinations, for example 'wet diaper'. Brown (1973)[19] observed that 75% of children's two-word utterances could be summarised in the existence of 11 semantic relations:

Attributive: 'big house'

Agent-Action: 'Daddy hit'

Action-Object: 'hit ball'

Agent-Object: 'Daddy ball'

Nominative: 'that ball'

Demonstrative: 'there ball'

Recurrence: 'more ball'

non-existence: 'all-gone ball'

Possessive: 'Daddy chair'

Entity + Locative: 'book table'

Action + Locative: 'go store'

Eleven important early semantic relations and examples based on Brown 1973[19]

At around 3 years, children engage in simple sentences, which are 3 word sentences. Simple sentences follow adult rules and get refined gradually. Grammatical morphemes get added as these simple sentences start to emerge.[citation needed]

By 3–5 years, children continue to add grammatical morphemes and gradually produce complex grammatical structures.[citation needed]

By 6–10 years, children refine the complex grammatical structures such as passive voice.[citation needed]

Pragmatics development[edit]

From birth to one year, babies can engage in joint attention (sharing the attention of something with someone else). Babies also can engage in turn taking activities.[citation needed]

By 1–2 years, they can engage in conversational turn taking and topic maintenance.[citation needed]

By ages 3–5, 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.[citation needed]

By age 6-10, shading occurs, which is changing the conversation topic gradually. Children are able to communicate effectively in demanding settings, such as on the telephone.[citation needed]

The Consequences of Bilingualism on Language Development[edit]

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.[20] Another perspective dictates that the second language will just confuse the child and prevent them from mastering their primary language.[21] Studies have shown that American bilingual children have greater cognitive flexibility, better perceptual skills and tend to be divergent thinkers than monolingual children between the ages of five to ten.[20][21] However, studies comparing Swedish-Finnish bilingual children and Swedish monolingual children between the ages of five to seven have also shown that the bilingual children have a smaller vocabulary than monolingual children.[22] 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.[23] 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.