lcs 11: cognitive science - language acquisition...language acquisition jesse a. harris march 25,...
TRANSCRIPT
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
Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 2
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?
Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 3
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
Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 4
Segmentation problem
(1) Thisisanaverageexampleofaspeechstream.
Segmentation problemThere are rarely deVnitive pauses between words in a speechstream. How can the child learn how to recognize wordboundaries?
Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 5
Segmentation problem
This an average example of a speech stream
Segmentation problem
Time (s)0 2.194
-0.1477
0.2003
0
Segmentation problem
Segmentation problem
(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)
Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 9
Segmentation problem
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.
Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 10
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.
Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 11
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!
Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 12
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?
Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 13
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.
Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 14
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).
Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 15
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
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
Wug test Wug test
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/
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
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
Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 24
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