1. Brain Mechanisms in Early Language Acquisition
Kuhl, P.K. (2010)

2. Why does this paper matter?
Personal interests in ESL Education; bilingual acquisition
Baseline for understanding critical factors in language development (eg; linguistic environment)
Professor Aslin’s research (statistical learning)
Your own experiences with infants acquiring language?

3. Also, what does it mean to acquire a language?
“The Critical Period”
Language acquisition past age 7 becomes way more difficult
Has led to consensus about a ‘biological critical period’ for language learning
Infants and young children are so much better at this than we are,
Why? How does this even happen?
Also, what does it mean to acquire a language?
Infants are ridiculously better at ‘language acquisition’ as a whole, but to look at how this works we have to consider what acquisition means? Could simply try to look at it as a level of proficiency… but to be proficient you could say we have to: be able to comprehend complex sentences and produce coherent ones; before that, have to be able to know the words in the sentence, that there is a certain way of ordering them based on their relationships with each other to convey meaning; before knowing even the words, we need to know the SOUNDS that make up the words in our vocabulary. *Aslin does research on how infants segment speech to determine possible word candidates before learning words…but Kuhl’s research is preliminary in looking at how infants discriminate speech sounds (foundational unit)

4. Why are infant’s seemingly able to “crack the speech code”?
Her hypothesis of neural commitment is the idea that infants develop the neural circuitry and mechanisms very very early to allow them to detect certain speech patterns (e.g. like phonetic distributions)
Kuhl’s hypothesis: Native Language Neural Commitment (NLNC)

5. In the context of the paper…
A more specific critical period is discussed in relation to phoneme perception
Infants are able to perceive/distinguish between phoneme categories that apply to all languages
Up until about 9 months (6-12 months as a more general frame)
What’s happening at 9 months?:
“perceptual narrowing”
Eg english vs Japanese infants discrimination between /r/ and /l/ phonemic categories
As they receive culminating linguistic information from their environment, babies kind of tune their perception of speech sounds in a way that’s relevant to their language. So basically- distinct /r/ and /l/ categories as they exist in English don’t exist in Japanese- it’s kind of lumped into one /r/ ish category. So: it doesn’t make sense for Japanese babies to keep representations of these distinct categories when they’re irrelevant so they essentially “unlearn” them.
This is pretty different than other cognitive processes- you kind of imagine that as our brains develop we become more and more able to do eg. math but with language learning it’s the opposite- we are born with the ability to learn sounds from all languages but then kind of determine which ones are important to keep and unlearn the rest.
^interesting question from ted talk: do bilinguals keep track of two separate phonemic systems then and just transition between them?

6. Native vs. Non-native Phonemic Discrimination (with /r/ and /l/)
So how exactly do they perceptually tune -> statistics

7. How do computational processes and social learning interact and influence language processing during development?
Computational processes eg statistical learning vs “the social brain”

8. Computational Processes
*STATISTICAL LEARNING
Rich linguistic environment!
Take statistics: find distributions of formants, classify them into phoneme categories relevant to the language
This is a basic implicit learning mechanism that generalizes to other cognitive processes, but it’s especially helpful in phoneme perception!

9. Distribution of Formants

10. Example: Taiwanese and English native vs nonnative proficiencies
So what happens when we expose babies to a new language during this sensitive period?
Taiwanese and English babies tested on a phoneme category distinction that exists in taiwanese: are at same proficiency before 9 months, taiwanese babies are more proficient after 9 months; eng babies are way worse after 9 months. Then, another part of experiment where 9 month old english babies are exposed to taiwanese linguistic input in a relatively unstructured way for 4-5 weeks….become just as proficient as taiwanese babies who have been exposed for their whole life/10 months. So clearly: babies take statistics on any kind of input they receive and use it to their advantage.
Example: Taiwanese and English native vs nonnative proficiencies

11. Types of Exposure
THEN looked at role of personal interaction: eng babies separated to get taiwanese linguistic exposure through a. television (audio and visual input cues) b. tape recording (audio cues only) -> in both situations, this learning of taiwanese phonemic contrasts did not happen. They performed just as if they had gotten no input at all. That’s super weird- that means it has to be more than just statistical inference?

13. Is there something else playing a role here?

14. “The Social Brain”; Social Gating Hypothesis
Refers to idea of social factors controlling the extent to which computational mechanisms aid language learning *key to note: social learning and computational learning are still thought to be jointly involved

15. Social gating may operate based upon
Social brain as a necessary explanation for acquiring complex/natural language
Social gating may operate based upon
Increased attention and/or arousal*
More information
A sense of a relationship with the provider
Activation of brain mechanisms linking perception and action
Social cues (eye gaze, pointing, face/mouth articulation)
BASICALLY social gating is the idea that the social brain/our innate condition to be social creatures controls the timing of when certain computational processes like statistical learning are used.
The relevance of social cues like eye gaze have been measured using ERP, specifically by looking at mismatch negativity that basically indicates that a large mismatch/neural discrimination of phonemic contrasts is directly related to an increase in gaze shifts between ‘tutor’/provider and newly introduced objects [considering inserting linear graph]

16. How can we relate this all back to the broader critical period and NLNC?
Ideas for this slide: talk briefly about how it has led us to be able to predict overall language proficiency up to 2 years of age …18-30 months. (reinforced not only by behavioral but by mismatch negativity)
NLNC-that there has been a recognition for what we need to learn as relevant, the implicit learning going on here (a combination of statistical learning and social learning) is what shapes the brains neural circuitry- it adapts in a way to make learning easier for the relevant language and ‘decreasing perception’ for input that is then characterized as non-native. Goes back to more general cognitive concepts of attention and inhibition

17. More hypotheses regarding the aid of social contexts?
Mirroring
Sensory-motor learning (perception and action)
Collected from MEG and fMRI- found linkages to Broca’s area, inferior temporal, and motor areas
Sensory motor learning that basically they’ll store a memory representation of that audio signal and then try to approximate towards this representation

18. Goals for Future Research
Relative time frames for critical periods at all levels of language
Their overlaps
Why the may differ
How brain systems are linked and work together early in development
General research on brain rhythms
Increased cognitive abilities (later paper?)
Opening and closing for critical periods for all level of language and how they overlap and why they differ
Brain systems responsible for speech production and perception forge a link early in development and how they respond in different contexts
Brain rhythms
Cognitive effects of speech/language learning- in specifics to bilingualism coming up later?

19. Personal questions
A more solidly defined link between neuroanatomy and the ease of early language acquisition
-NLNC as a starting point -More thorough research regarding sensory motor systems and their role
Bilingualism is only briefly explored

20. Questions and Commentary?