lcs 11: cognitive science - language acquisition...language acquisition jesse a. harris march 25,...

Pomona College

LCS 11: Cognitive ScienceLanguage acquisition

Jesse A. Harris

March 25, 2013

Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 1

Agenda

Nature vs. nuture divide

Poverty of the stimulus and reactions Critical period

Replication projects

Class evaluations


Big picture

Three related questions in acquisition research

1. What abilities or skills are required to learn a language?

2. When do these abilities emerge? What speciVc stages arethere in language development?

3. What other cognitive abilities, if any, do these abilitiesdepend on?

Raises the all important questionWhat constitutes a knowledge of language?What kind of knowledge does a native speaker have about his or herlanguage?


Abilities

Just what abilities and skills are required to learn a language?

1. Perceive the appropriate linguistic sounds

2. Distinguish words and other meaningful elements inspeech stream

3. Pair elements in stream with meanings

4. Structure those elements into more complex structures

5. SuXcient interaction with language in use


Segmentation problem

(1) Thisisanaverageexampleofaspeechstream.

Segmentation problemThere are rarely deVnitive pauses between words in a speechstream. How can the child learn how to recognize wordboundaries?



This an average example of a speech stream


Time (s)0 2.194

-0.1477

0.2003

0



(2) a. Two dults (Uttered)b. Two adults (Target)

(3) a. I don’t want to go to your ami (Uttered)b. I don’t want to go to your Miami (Target)

(4) a. I am being have! (Uttered)b. I am behaving! (Target)



Phonological bootstrappingChildren use statistical regularities to determine likely wordboundaries.

I Infants can’t use top-down knowledge to infer wordsI Must make the most of the inputI SaUran et al (1996) proposed that infants use transitional

probability measures to infer boundaries.


Segmentation problemTransitional probabilitiesThe probability of one sound X given another Y:

P(Y|X) = P(XY)P(X)

≈ freq(XY)freq(X)

I Languages regulate what sounds can go together within aword, but not so much at a word boundary.Within word High transitional probabilitiesBetween word Low transitional probabilities

(5) pretty# babypre + ty is high within word; ty + ba is low.


Nature vs. Nuture

NatureChild’s acquisition oflanguage is acheivedprimarily through innateknowledge.

I Universality in grammarI Specialized learning

deviceI Inborn biases and

defaultsI Similiar development

NutureChild’s acquisition oflanguage is acheivedprimarily through exposure.

I Statistical regularitiesI Model learning with

limited memoryI Child directed speech

Plausibly elements of both!


Nuture

B.F. Skinner

The extreme case of behaviorism:

Simple set of reward-based generallearning principles that child uses tolearn language. No previousknowledge or expectations.

QuestionDoes this view seem reasonable?What might be some intuitiveconcerns about such a view?


Nature

Noam Chomsky

Impossible!

1. Too many possible responsesgiven stimuli

2. Ignores complexity andcreativity of language structures

3. Too little exposure to developrich knowledge throughimitation.


Nature

Noam Chomsky

Instead, children acquire language byusing an innate knowledge oflanguage, along with very powerfullanguage speciVc learning biases.

Innate knowledge of language isabstract, and known as UniversalGrammar (UG).


Nature vs. NuturePoverty of the stimulus argumentThe language that children acquire goes beyond the input thatthey receive. Language is unlearnable from exposure alone.

In support

I Limited negativeevidence

I Children seemunresponsive tocorrection

I Grammatical judgmentsfor novel forms

I Relative uniformity indevelopment

Child My teacher holded the rabbits and we pattedthem.

Adult Did you say the teacher held the baby rabbits?

Child Yes.

Adult What did you say she did?

Child She holded the baby rabbits and we patted them.

Adult Did you say she held them tightly?

Child No, she holded them loosely.

Jean Berkohttp://www.onbeing.org/program/unfolding-language-unfolding-life/256


In support





Wug test Wug test

http://www.onbeing.org/program/unfolding-language-unfolding-life/256

Wug test Wug test

I Full Wug test materials:http://childes.psy.cmu.edu/topics/

I Video of Berko Gleasondescribing her work:http://video.pbs.org/video/1608569948/


In support





CounterclaimsI Underestimates negative

evidenceI Children learn language

piecemeal according tocognitive limitations

I Unclear how a rich UGwould be innatelyencoded

Critical period

Developmental limitationsAcquiring a language requires that the child be exposed tosuXcient language input within a developmental timewindow.

I Estimates vary: 5 years – pubertyI Period of neural plasticityI BilingualismI ProfeciencyI Failure to develop languageI Critical period observed in other species


http://childes.psy.cmu.edu/topics/

http://video.pbs.org/video/1608569948/

Critical period

I Severely abused and isolatedI Discovered at age 13 without

having acquired speechI Eventually able to acquire a

limited vocabulary, but never afully complex linguistic system.1. Few grammatical words2. No auxiliaries3. Improper verbal and nominal

inWection4. No passives5. Negation limited

lcs 11: cognitive science - language acquisition...language acquisition jesse a. harris march 25,...

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