Language is central to human development and it infiltrates all areas of the curriculum.
We can appreciate how complex it is for children to develop language skills if we spend a moment considering the range of elements this requires, including speech production, comprehension and understanding of speech sounds and visual symbols. If those skills are impaired in any way, it is a cause for concern. And there are many ways those impairments can present themselves, from dyslexia and difficulties with grammar acquisition to problems understanding others, such as autism.
On top of that, an expectation is returning to schools that pupils need to master more than one language. And there is an increasing drive to teach modern foreign languages in primary.
So it is perhaps not surprising that neuroscientists have put a considerable amount of research effort into understanding language development, both in terms of the brain areas involved and the processes that activate these regions.
For example, the common idea of language being lateralised to the left hemisphere is upheld by neuroscience research and specific areas -modestly named after the researchers that found them - are implicated in speech production (Broca's area) and speech comprehension (Wernicke's area). A specific visual word area has even been posited, although this is still controversial. Interestingly, these areas of the brain seem to be involved irrespective of the actual language being developed and are also active during use of sign language.
Neuroscientists have also investigated three main aspects of language processing: phonological (sentence melody and speech sounds); lexical-semantic (word forms and meanings) and syntactic processing (grammatical relationships).
A map of development has been devised through scientific research and we now know that, within the first year of life, babies develop language perception and production skills, culminating in word-object associations and production of words. This development continues at a fast rate and, by the time children reach the classroom at the age of 4, their brain will show distinct electrical reactions to syntactically and semantically abnormal sentences, in a similar manner to that seen in the adult brain.
For the majority of children, these developmental milestones will be met and language will develop accordingly. So, rather than focusing entirely on language disorders, research has also investigated the development of a second language. Of course, a key difference between learning a first and second language is that the latter happens later, but what does this actually mean for language development?
In the late 1960s a bleak picture was painted, with the "critical period hypothesis" suggesting that only a language learned before puberty could reach levels of natural proficiency because of limitations in the plasticity - or adaptability - of the motor and auditory systems in the brain.
However, although there is evidence for this limited plasticity, there is also evidence suggesting that there are exceptions to this constraint. For example, context is thought to make a significant difference and, where a multilingual context necessitates language learning, native proficiency can be achieved. Therefore, the negative "critical period" view perhaps paints too static a picture of language development, which in reality is likely to alter with age, context and ability.
Research has also demonstrated that other factors can affect language development. For example, recent research from Italy has shown a relationship between temperament, as assessed by day-care teachers, and different levels of linguistic competence. The researchers found that inattentive and inhibited children showed poorer lexical and morphological abilities and a more immature vocabulary, compared with children who did not have these traits. In another study, scientists showed that poor sleep during the first two years of life may be a risk factor for language learning.
In summary, research from neuroscience has demonstrated that language development begins in the newborn and progresses at an astounding pace - the brain begins to function in a manner similar to that found in adult subjects by the time children reach primary school. In addition, while the early ideas of a critical period may have been overly pessimistic, on the whole, language is best learned when younger. Language development can also be both impaired and supported by a number of factors.
Dr Ellie Dommett is a lecturer at the Open University and co-author of the Learning and the Brain Pocketbook
Dionne, G. et al. "Associations Between Sleep-Wake Consolidation and Language Development in Early Childhood: a longitudinal twin study" (2011). Sleep 34 (8), 987-95
Friederici A.D. "The Neural Basis of Language Development and its Impairment" (2006). Neuron 52 (6), 941-52
Garello, V. Viterbori, P. and Usai, M.C. "Temperamental Profiles and Language Development: a replication and an extension" (2012). Infant Behavior and Development 35 (1), 71-82
Simmonds, A.J. Wise, R.J. and Leech, R. "Two Tongues, One Brain: imaging bilingual speech production" (2011). Frontiers in Psychology 2, 166.