LCS 11: Cognitive Science Results of evaluations Perception in - - PowerPoint PPT Presentation

Pomona College

LCS 11: Cognitive Science

Language acquisition 2

Jesse A. Harris April 1, 2013

Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 2 1

Agenda

֠ Results of evaluations ֠ Perception in language acquisition

֠ Prosody in womb ֠ Categorical percetion ֠ Loss of perceptual ability

֠ Effects of general context

Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 2 2

Perceptual abilities

Main question for today

How early do perceptual abilities appear in language acquisition?

◮ Attend to rhythmic and language specific properties very

early, even in the womb!

◮ Sucking rate experiments – very early preference for

familiar language

◮ We’re born to learn any possible language, but we quickly

specialize.

Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 2 3

Knowledge of language – sound

Phones

What sounds the language uses in its inventory. E.g., English uses the voiceless dental stop [t] sound but not, say, bilateral fricatives [B].

Phoneme

What sounds are distinctive in a language, i.e., can constitute a meaningful distinction. (1)

• a. pat

(voiceless)

• b. bat

(voiced)

• c. phat

(aspirated)

Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 2 4

Knowledge of language – sound

Prosody

The contour that overlays speech pattern, including rhythm, volume, stress, pitch, duration, emphasis, and contrast. Also can convey an expressive dimension of communication. (1)

• a. You’re gonna eat that?
• b. You’re gonna eat that!

◮ Language learning starts with prosodic – especially

rhythmic – patterns in the womb!

◮ Foetus develops in amniotic fluid protected by layers

skin, fat and muscle. Only limited range of sounds pass through (1000Hz; Altmann 1997)

http://www.youtube.com/watch?v=_JmA2ClUvUY

Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 2 5

Processing prosody in the womb

DeCasper et al 1994: mothers read a short nursery rhyme aloud for 4 weeks during late pregnancy. Heart rate of the foetus decreased when the familiar rhyme was read as compared to a novel one. Z Yet, not enough information to distinguish within language sounds.

Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 2 6

Processing prosody out of the womb

Newborns able to distinguish prosody of parents’ language from other languages (with significantly different prosodic structure).

◮ 4 day old infants from

monolingual French families

◮ Compated filtered French v.

English speech.

◮ Infants sucked faster when

presented with novel prosody, indicating that they recognized the French prosody as familiar.

http://psych.rice.edu/mmtbn/language/sPerception/infantsucking_h.html

Complications

String of pearls model

Assume a one-to-one correspondence between acoustic signal and the phonetic category. Listener maps sound onto a string.

Coarticulation

When a sound takes on the characteristics of another sound due to proximity to it. (2) Pronounce the following naturally: Is the ’n’ the same?

• a. ten
• b. tenth

(3)

• a. lean dog
• b. lean bacon

Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 2 8

Categorical perception

◮ Despite continuous spectrum,

perceive differences as categorical.

◮ Voice onset time: the time

between a stop and the begining of voicing (vibration

• f vocal cord).

◮ Don’t distinguish until

boundary. Experiment on synthetic ba, da, ga

http://www.ling.gu.se/∼anders/KatPer/Applet/index.eng.html

Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 2 9

Categorical perception

Part 1: Identification

Identify which syllable you hear from selection of two

• r three: shift in perception

is abrupt, as you don’t perceive within category differences.

Part 2: Discrimination

Discriminate between sounds well at boundary, but poorly within category.

Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 2 10

Categorical percetion

Development of categories

◮ Categorical perception is learned. ◮ Infants are universal listeners – able to distinguish any

phonetic contrast.

◮ But sensitivity rapidly decreased within first year.

Categorical perception in development

Develop limited sensitivity to phonetic contrasts: perceive irrelevant differences, e.g., /p/ and /ph/ as the same phonemic category in English, or /r/ and /l/ in Japanese and Korean.

Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 2 11

Universal listeners

Conditioned head turn procedure

◮ New phoneme randomly introduced ◮ Infant is rewarded when they detect the change

http://www.youtube.com/watch?v=dAU5CAl1U6M

Rapid decline in sensitivity

◮ Infants 6 –10 mo. able to distinguish two non-native

contrasts, e.g., Hindi /t/ and /T/. Ability vanishes after this (unless excessive training).

http://www.youtube.com/watch?v=Ew5-xbc1HMk

Jesse A. Harris: LCS 11: Cognitive Science, Language acquisition 2 12

◮ Left – decline of

sensitivity to Hindi contrasts

◮ Right – decline

• f sensitivity to

Nthlakapmx contrasts

In a nutshell . . .

Lose perceptual sensitivity when we do not need to maintain it

Effects of context

Adult listeners depend on contextual knowledge as well

• 1. Phonemic restoration

http://www4.uwm.edu/APL/players/TI_SPR.html

Warren and Warren 1970 presented sentences with

• bscured phones; restoration of the syllable depends on

the surrounding context. (7) It was found that the *eel was on the ...

• axle
• shoe
• range
• table
• 2. Non-linguistic context

http://www.youtube.com/watch?v=KiuO_Z2_AD4