Доклад: Language Acquisition in Infants

Running head: Language Acquisition in Infants

Language Acquisition in Infants

Yelizaveta Mirkovskaya

University of California, Los Angeles

Language Acquisition in Infants

The unknown has always puzzled the human brain. When marvelous scientific

technologies were unavailable to solve the mystery of human intelligence,

scientists made numerous guesses as to which processes might underlie the

smooth and complex functioning of the brain; modern technologies made it

possible to look inside the human scalp and start decoding Nature’s most

complex creation – the human mind. Language is an extremely essential

attribute of human beings, which distinguishes them from the rest of the

animals. However, its mystery started to be unwound only recently.

How humans acquire ability to separate and construct words is one of the

central questions of the modern research in the field of language

acquisition. It has been proposed that to construct words, human infants use

sequential probabilities; that is, they are innate mathematicians and use

simple statistics to perceptually categorize particular sound groups,

calculate their frequency in the ambient stream of sounds, and predict which

group of sound should follow the certain other one. For example, Japanese,

Swedish, and English infants (i.e., representatives of different types of

languages) demonstrate increased sensitivity to the phonemes and prototype

vowels specific to their language, and do not respond as highly when hearing

phonemes and vowels pertaining to languages, other than their native one. The

experiment on eight-months-old infants also showed that when discriminating a

change from a particular syllabus to another one in the string of syllabi

(i.e., “de” to “ti”), infants who succeed the most are the ones who learn a

pattern of syllabi in the sequence (i.e., perceive combinations of certain

syllabi as words) by learning that the sequential probability of a certain

syllabi given a certain other syllable is one; that is, the syllable will

undoubtedly occur. As hypothesized, learning to chunk certain syllabi into

words on the basis of statistical frequency reduced perceptual demands of the

lingual task for the infants, and made it easier for them to fulfill the task

of distinguishing one syllable from another. Another experiment on infants,

based on the fact that infants pay more attention to novel stimuli,

demonstrated that once having heard the two-minute strings of invariantly

repeated syllabi (their order was not changed), infants showed novelty

preference when they heard an unexpected order of syllabi when tested by

listening to three-syllabi chops of the two-minute sequence. Since the pure

statistical frequency of occurrence of all of the three syllabi was the same,

it was the sequential probability of occurrence of a certain syllabus that

made the infants heighten their attention to the crossing-word-boundaries

combinations. In addition, even younger infants are able to discern the

prosodic pattern (trochaic, with the stress on the first syllable of the

word, or iambic, with the stress on the second one) of the native language,

based on the sequential computations.

Sequential probabilities are definitely important to acquisition of language

skills in infants, but they are not the only mechanism of mastering a

language. Rigid neural networks, produced in the first year of life, encode

the patterns of native language and interfere with the ones of foreign

languages. This way, it is easier for the infant to keep learning the native

language as more and more neural paths and connections are created in the

brain; growing number of these native connections interferes with creating

different ones for foreign languages. When adults are subjected to hearing

foreign speech, larger areas of their brains are illuminated for longer times

during magnetoencephalography as compared to when they hear native speech,

which indicates that more effort is required on the part of the adult to

process the speech sounds. Similarly, infants’ language skills at an older

age strongly correlate with their speech discrimination skills later in

development. A longitudinal research on seven- and eleven-months old infants

showed that at the age of seven months, infants still discriminate between

native and non-native consonant combinations, whereas at the age of eleven

months this discrimination is almost absent. This distinction illustrates the

fact that with age, neural networks underlying acquisition of language

strengthen and filter out foreign sound combinations more effectively. If it

were not for neural commitment of neural networks, infants should have

reacted to combinations in each language equally strongly. Neural commitment

is also said to be responsible for the “sensitive period” during language

acquisition, during which, according to the NLNC (Neural Language Neural

Commitment) model, brain networks solidify and become more sensitive to the

patterns of native language. Sensitive period closes, when neural networks

stabilize (i.e., become neurally committed).

As suggested in the article, neural networks stabilize when they stop being

sensitive to speakers’ individual differences in pronunciation of various

speech sounds; that is, when infants’ representations of sound distributions

become stable and rigid. In this regard, bilingual children’s neural networks

should take longer to stabilize since there is simply more of them (at least,

two systems instead of one), and the perceptual load on a bilingual

individual’s brain is much greater. A longitudinal quasi-experiment could be

performed to test this hypothesis. Participants in this experiment -

bilingual and monolingual infants at ages of six, nine, twelve, fifteen,

eighteen, twenty one, and twenty four months – will be subjected to hearing

series of computer-generated sounds, demonstrating different pronunciations

of the same vowel. Each vowel will play for about two or three minutes in

order to give infant enough time to familiarize with the task; about five

vowels will be tested with the order of their appearance counterbalanced, as

to control for the order effects. Some distracter sounds will be played

between the presentations of the vowel, so that the infant does not get used

to the simply presence of a monotonous sound from the source. The dependent

variable in this experiment – the sensitivity of an infant to different

pronunciations of the same vowel – will be tested by observing infants’

instances of behaviors caused by distracting novelty (turning of the head

towards the sound source, interrupting the on-going activity, etc.) while the

sound is playing. The more distracting behaviors observed, the more sensitive

the infant is to the differences in presentation of the same sound. Any

extraneous variables that might interfere with the results will be kept

roughly constant: participant infants will be taken from families of similar

socio-economic status and will be of similar health conditions, sounds played

will be the same throughout the whole experiment, infants will be tested on

the day when they reach the next appropriate age for testing, lab conditions

will be kept constant for all of the infants and throughout the length of the

experiment. The experimenters will make sure that for the bilingual group of

children, they will be exposed to the non-English language equally often as

to the English language throughout the whole experiment; for the monolingual

group of infants, they will not be exposed to any language, other than

English.

The results of this experiment, if consistent with the hypothesis, will show

that more distractive behaviors will be observed in bilingual infants because

of higher perceptual load of two languages on their brain. For the

monolingual group, less distractive behaviors due to novelty stimulation will

be observed. If, for example, for monolingual children, neural networks will

stabilize by the age of one year, then, for bilingual children, the neural

networks will be committed at the age of about fifteen months; that is, later

(these ages are hypothetical).

Language acquisition in human infants is a starting-to-be-resolved mystery to

the mankind; its resolution will help to treat children with linguistic

problems and ameliorate language learning in healthy children.