Speech information - the smallest sound elements in speech may not be the basis for babies to learn language as previously thought. Instead, babies learn language from rhythmic information - changes in syllable emphasis in speech - which, unlike speech information, is heard in the womb.
Babies don't begin to reliably process speech information until they are seven months old -- too late, researchers believe, to form the basis of language.
Researchers say parents should use sung lyrics, such as nursery rhymes, to talk to their babies as early as possible. This is because babies learn language in their first few months from rhythmic information rather than phonological information.
Rhythmic language and speech information
Phonetic information - the smallest sound elements in speech, often represented by the alphabet - is considered by many linguists to be the basis of language. It is thought that babies learn these small sound elements and add them together to form words. But a new study suggests that speech information is learned too late and too slowly to do this.
In contrast, rhythmic speech can help babies learn language by emphasizing the boundaries of individual words, even in the first few months of life.
Researchers from the University of Cambridge and Trinity College Dublin investigated how well babies process speech information in their first year of life.
Their study, published today (December 1) in the journal Nature Communications, found that speech information is not successfully encoded until babies are 7 months old, and is still sparse by the time babies start speaking their first words at 11 months old.
Professor Usha Goswami, a neuroscientist at the University of Cambridge, said: "Our study shows that although most babies can recognize familiar words such as 'bottle' by around 7 months, individual speech sounds are not reliably processed until around 7 months. From then on, individual speech sounds are still added very slowly - too slowly to form the basis of language."
Researchers recorded the brain electrical activity patterns of 50 4-, 7- and 11-month-old babies while they watched a video of an elementary school teacher singing 18 nursery rhymes to the babies. The low-frequency brain waves "read" the encoded speech information through a special algorithm.
Researchers have found that babies' speech coding gradually emerges in the first year of life, starting with labial sounds (such as d for "daddy") and nasal sounds (such as m for "mom"), and the "read" speech information gradually becomes more like adult speech information.
Lead author Professor Giovanni Di Liberto, a cognitive and computer scientist at Trinity College Dublin and a researcher at the ADAPT Centre, said: "This is the first evidence we have of how brain activity related to speech information responds to continuous speech over time."
Previous studies have mainly compared responses to nonsense syllables, such as "bif" and "bof." New research recommends parents use rhythmic language, such as nursery rhymes, with babies because babies learn language from rhythm, not speech. Research shows that babies process rhythmic speech as early as two months old, affecting language development and potentially having implications for conditions such as dyslexia.
The current study is part of the Baby Rhythms project led by Goswami, which is investigating how language is learned and how this relates to dyslexia and developmental language disorders.
Goswami believes that rhythmic information - the stress or emphasis on different syllables in words and the rise and fall of intonation - is key to language learning. A companion study from the Baby Rhythms project shows that infants as young as two months old can process rhythmic language information, and that individual differences predict later language outcomes. This experiment was also conducted with adults who showed the infants the same rhythm and syllable "reading".
"We believe that language rhythm information is the implicit glue that supports the development of a fully functioning language system," Goswami said. "Infants can use rhythm information as a scaffolding or skeleton on which to add speech information. For example, they may learn that English words generally have a strong-weak rhythm pattern, such as 'daddy' or 'mummy,' with stress on the first syllable. When listening to natural speech, they can use this rhythm pattern to guess where one word ends and another begins."
She added: "Parents should talk and sing to their babies as much as possible, or use infant-guided language such as nursery rhymes, as this will have an impact on language outcomes. Rhythm is a common feature of every language around the world. In all languages that babies are exposed to, there is a strong beat structure, with two strong syllables per second. Biologically, we emphasize this when speaking to babies."
Attempts to explain dyslexia and developmental language disorders in terms of phonological problems have a long history, but the evidence is weak. She believes that individual differences in children's language stem from rhythm.