Unipd research. How a mother’s language shapes the newborn brain
29.11.2023
We know from experience that it is much easier to learn a language as a child than as an adult. The so-called "window of opportunity" demonstrates that the first months and years of development are fundamental for language acquisition. Learning a second language as an adult is much more difficult, furthermore, the acquisition of language begins during the pregnancy as a fetus can hear the sound that propagates - albeit distorted - inside the mother's womb. Children, therefore, hold some exposure to the language spoken by their mothers even before they are born.
The study “Prenatal experience with language shapes the brain” published in Science Advances by researchers from the University of Padua investigates how the brains of newborns are influenced by their previous exposure to language.
Researchers from Unipd explain, “We asked ourselves how the activity of newborns' brains changes after hearing sentences in their own language or in other languages and we hypothesized that these changes are the neural basis of learning the mother tongue. We then moved on to measure the infants' neural activity as they listened to sentences in French, their native language, as well as in Spanish and English, two unfamiliar languages. All this using electroencephalography, a standard technique for measuring neuronal activity. Our study shows that neuronal activity is more complex after exposure to the native language and preserves a memory of neuronal responses given in the past. In fact, these responses become more frequent.”
To measure this form of complexity in the time domain we used a technique called Detrended Fluctuation Analysis (DFA) which helps to understand how well a system remembers what happened before and does so by measuring how similar a process is to itself at different time scales. We can call self-similar a process in which small variations recur in the same way even on longer time scales (as when a melody repeats itself in a recognizable way); on the contrary, completely random processes (such as the numbers generated by rolling dice) do not show any type of regularity, or memory, and therefore have a lower complexity in their temporal structure.>The main result of the DFA is a number α, called the "Hurst exponent": it is this α that holds the key to the "memory" of the neuronal signal. The larger α is for a signal, the more past experiences influence what happens next which corresponds to processes. The larger α is for a signal, the more past experiences influence what happens next which corresponds to more complex neuronal processes.
We found that when a newborn is made to listen to the language they were exposed to in utero their brain activity shows a peak in α, which does not happen when the language is different. This fact – says Judit Gervain of the Department of Developmental and Social Psychology of the University of Padua – indicates that in the brain of newborns, exposure to the mother tongue triggers brain processes of a complex nature, neuronal dynamics which are probably associated with language learning. These processes are much less strong when newborns hear another language, and we can conclude that they were generated and evolved during prenatal development.
In other words, the newborn's brain seems to be structured to remember and respond differently to the language it has heard before birth and this greater response indicates a sort of linguistic "privilege" that shapes the early stages of language learning. This is a revelation – concludes Professor Gervain – which highlights the extraordinary ability of the brain to adapt, especially in relation to the great complexity of human language."
