Neural Substrates of Language Acquisition

Patricia Kuhl and Maritza Rivera-Gaxiola

Neuroimaging is being used with infants. "The goal on experiments on infants has been to determine whether the initial state and the learning mechanisms are speech specific and species specific."

"The combination of computational and social abilities may be exclusive to humans (Kuhl 2007)."

"The studies suggest that exposure to language in the first year of life begins to set the neural architecture in a way that vaults the infant forward in the acquisition of language."

EEG/ERP is inexpensive, noiseless, "excellent temporal resolution"

At birth infants are capable of distinguishing between all phonemes that are possible in human languages, but with exposure to the native language, infants learn to "tune out" the phonemes that are not distinguished in their native language.

"By the end of the first year, the infant brain is no longer universally prepared for all languages, but instead primed to acquire the language(s) to which the infant brain has been exposed."

So adults truly cannot learn a second language the same way infants learn their first.

In a study (Kuhl et al 2003), a group of infants exposed to a live person speaking Mandarin were able to distinguish Mandarin sounds, while groups exposed to television and audio Mandarin tested the same as groups that were never exposed to Mandarin at all. So social interaction is very important to infant language acquisition. This could be due to the ways humans learned language for centuries--we could be evolutionary accustomed NOT to learn language from computers.

"A sudden increase in vocabulary typically occurs between 18 and 24 months of age--a "vocabulary explosion" (Granger & Brent 2004, Fernald et al. 2006)--but word learning begins much earlier. Infants show recognition of their own name at four and a half months (Mandel et al. 1995)." p. 520

"new words may be encoded in the same neural regions as previously learned words."

""Newborns tested by Imada et ak showed no activation in motor speech areas for any signals, whereas auditory areas responded robustly to all signals, suggesting that perception-action linkages for speech develop by three months of age as infants produce vowel-like sounds."

"Studies across languages showed that by one year of age infants do not accept mispronunciations of common words, words in stressed syllables, or monosyllabic words, indicating that their representations of these words are well-specified by that age." references omitted

Researchers are "strongly interested" in which comes first: phonemes or words, or if learning is bidirectional.

Data on bilingual infants has conflicting results.

Some believe that it may take bilingual infants longer to accumulate a normal vocabulary in their native languages because of decreased input. There have not been many studies on bilingual infants.