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.Adger D. (2015). Syntax. Wiley interdisciplinary reviews. Cognitive science, 6(2), 131–147.
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. 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. 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. Similarly, it has 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. Further research has indicated the influence of the FOXP2 gene.
Stages
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: