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Quantifying Sensitivity. Quantifying Sensitivity. Response bias Two measures of discrimination Accuracy : how often is the judge correct? Sensitivity : how well does the judge distinguish the categories? Quantifying sensitivity Hits Misses False Alarms Correct Rejections

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Quantifying sensitivity1
Quantifying Sensitivity

  • Response bias

  • Two measures of discrimination

    • Accuracy: how often is the judge correct?

    • Sensitivity: how well does the judge distinguish the categories?

  • Quantifying sensitivity

    • Hits MissesFalse Alarms Correct Rejections

    • Compare p(H) against p(FA)


Quantifying sensitivity2
Quantifying Sensitivity

  • Is one of these more impressive?

    • p(H) = 0.75, p(FA) = 0.25

    • p(H) = 0.99, p(FA) = 0.49

  • A measure that amplifies small percentage differences at extremesz-scores


Normal distribution

Dispersionaround mean

Mean (µ)

√( )

∑(x - µ)2

n

Normal Distribution

Standard Deviation

A measure of dispersionaround the mean.


The empirical rule
The Empirical Rule

1 s.d. from mean: 68% of data

2 s.d. from mean: 95% of data

3 s.d. from mean: 99.7% of data


Quantifying sensitivity3
Quantifying Sensitivity

  • A z-score is a reexpression of a data point in units of standard deviations.(Sometimes also known as standard score)

  • In z-score data, µ = 0,  = 1

  • Sensitivity score d’ = z(H) - z(FA)


See excel worksheet sensitivity xls

See Excel worksheetsensitivity.xls



(Näätänen et al. 1997)

(Aoshima et al. 2004)

(Maye et al. 2002)


Normal distribution1

Dispersionaround mean

Mean (µ)

√( )

∑(x - µ)2

n

Normal Distribution

Standard Deviation

A measure of dispersionaround the mean.


The empirical rule1
The Empirical Rule

1 s.d. from mean: 68% of data

2 s.d. from mean: 95% of data

3 s.d. from mean: 99.7% of data


Normal distribution2
Normal Distribution

Standard deviation

 = 2.5 inches

Heights of American

Females, aged 18-24

Mean (µ)

65.5 inches



  • If we observe 2 people, how likely is it that they is at least 2 s.d. from the mean?both fall 2 s.d. or more from the mean?

  • …and if we observe 10 people, how likely is it that their mean score is 2 s.d. from the group mean?

  • If we do find such a group, they’re probably from a different population


  • Standard Error is at least 2 s.d. from the mean?is the Standard Deviation of sample means.



Development of speech perception in infancy

Development of Speech Perception in Infancy mean by 2 s.e., how likely is it that this group was drawn from the same population?


Voice onset time vot
Voice Onset Time (VOT) mean by 2 s.e., how likely is it that this group was drawn from the same population?

60 msec


Perceiving vot
Perceiving VOT mean by 2 s.e., how likely is it that this group was drawn from the same population?

‘Categorical Perception’


Discrimination
Discrimination mean by 2 s.e., how likely is it that this group was drawn from the same population?

A More Systematic Test

Same/Different

D

D

0ms 60ms

0ms

20ms

D

T

20ms

40ms

Same/Different

0ms 10ms

T

T

40ms

60ms

Same/Different

Within-Category Discrimination is Hard

40ms 40ms


Abstraction
Abstraction mean by 2 s.e., how likely is it that this group was drawn from the same population?

  • Representations

    • Sound encodings - clearly non-symbolic, but otherwise unclear

    • Phonetic categories

    • Memorized symbols: /k/ /æ/ /t/

  • Behaviors

    • Successful discrimination

    • Unsuccessful discrimination

    • ‘Step-like’ identification functions

    • Grouping different sounds


Three classics

Three Classics mean by 2 s.e., how likely is it that this group was drawn from the same population?


Development of speech perception
Development of Speech Perception mean by 2 s.e., how likely is it that this group was drawn from the same population?

  • Unusually well described in past 30 years

  • Learning theories exist, and can be tested…

  • Jakobson’s suggestion: children add feature contrasts to their phonological inventory during development

Roman Jakobson, 1896-1982Kindersprache, Aphasie und allgemeine Lautgesetze, 1941


Developmental differentiation
Developmental Differentiation mean by 2 s.e., how likely is it that this group was drawn from the same population?

UniversalPhonetics

Native Lg.Phonology

Native Lg.Phonetics

0 months

6 months

12 months

18 months


1 infant categorical perception

#1 - Infant Categorical Perception mean by 2 s.e., how likely is it that this group was drawn from the same population?

Eimas, Siqueland, Jusczyk & Vigorito, 1971


Discrimination1
Discrimination mean by 2 s.e., how likely is it that this group was drawn from the same population?

A More Systematic Test

Same/Different

D

D

0ms 60ms

0ms

20ms

D

T

20ms

40ms

Same/Different

0ms 10ms

T

T

40ms

60ms

Same/Different

Within-Category Discrimination is Hard

40ms 40ms


high amplitude sucking mean by 2 s.e., how likely is it that this group was drawn from the same population?

non-nutritive sucking


English vot perception
English VOT Perception mean by 2 s.e., how likely is it that this group was drawn from the same population?

To Test 2-month olds

High Amplitude Sucking

Eimas et al. 1971


General infant abilities
General Infant Abilities mean by 2 s.e., how likely is it that this group was drawn from the same population?

  • Infants’ show Categorical Perception of speech sounds - at 2 months and earlier

  • Discriminate a wide range of speech contrasts (voicing, place, manner, etc.)

  • Discriminate Non-Native speech contrastse.g., Japanese babies discriminate r-le.g., Canadian babies discriminate d-D[these findings based mostly on looking/headturn studies w/ 6 month olds]


Universal listeners
Universal Listeners mean by 2 s.e., how likely is it that this group was drawn from the same population?

  • Infants may be able to discriminate all speech contrasts from the languages of the world!


How can they do this
How can they do this? mean by 2 s.e., how likely is it that this group was drawn from the same population?

  • Innate speech-processing capacity?

  • General properties of auditory system?


What about non humans
What About Non-Humans? mean by 2 s.e., how likely is it that this group was drawn from the same population?

  • Chinchillas show categorical perception of voicing contrasts!

PK Kuhl & JD Miller, Science, 190, 69-72 (1975)


Suitability of Animal Models mean by 2 s.e., how likely is it that this group was drawn from the same population?

More recent findings…

Auditory perceptual abilities in macaque monkeys and humans differ in various ways

Discrimination sensitivity for b-p continua is more fine-grained in (adult) humans (Sinnott & Adams, JASA, 1987)

Sensitivity to cues to r-l distinctions is different, although trading relations are observed in humans and macaques alike (Sinnott & Brown, JASA, 1997)

Some differences in vowel sensitivity…

Joan Sinnott, U. of S. Alabama


2 becoming a native listener

#2 - Becoming a Native Listener mean by 2 s.e., how likely is it that this group was drawn from the same population?

Werker & Tees, 1984


When does change occur
When does Change Occur? mean by 2 s.e., how likely is it that this group was drawn from the same population?

  • About 10 months

Janet Werker

U. of British Columbia

Conditioned Headturn Procedure


When does change occur1
When does Change Occur? mean by 2 s.e., how likely is it that this group was drawn from the same population?

  • Hindi and Salishcontrasts testedon English kids

Janet Werker

U. of British Columbia

Conditioned Headturn Procedure


What do werker s results show
What do Werker’s results show? mean by 2 s.e., how likely is it that this group was drawn from the same population?

  • Is this the beginning of efficient memory representations (phonological categories)?

  • Are the infants learning words?

  • Or something else?


Korean has l r
Korean has mean by 2 s.e., how likely is it that this group was drawn from the same population?[l] & [r]

[rupi] “ruby”

[kiri] “road”

[saram] “person”

[irumi] “name”

[ratio] “radio”

[mul] “water”

[pal] “big”

[s\ul] “Seoul”

[ilkop] “seven”

[ipalsa] “barber”


3 what no minimal pairs

#3 - What, no minimal pairs? mean by 2 s.e., how likely is it that this group was drawn from the same population?

Stager & Werker, 1997


A learning theory
A Learning Theory… mean by 2 s.e., how likely is it that this group was drawn from the same population?

  • How do we find out the contrastive phonemes of a language?

  • Minimal Pairs


Word learning
Word Learning mean by 2 s.e., how likely is it that this group was drawn from the same population?

  • Stager &Werker 1997‘bih’ vs. ‘dih’and‘lif’ vs. ‘neem’


PRETEST mean by 2 s.e., how likely is it that this group was drawn from the same population?


HABITUATION mean by 2 s.e., how likely is it that this group was drawn from the same population?

TEST

SAME

SWITCH


Word learning results
Word learning results mean by 2 s.e., how likely is it that this group was drawn from the same population?

  • Exp 2 vs 4


Why yearlings fail on minimal pairs
Why Yearlings Fail on Minimal Pairs mean by 2 s.e., how likely is it that this group was drawn from the same population?

  • They fail specifically when the task requires word-learning

  • They do know the sounds

  • But they fail to use the detail needed for minimal pairs to store words in memory

  • !!??


One year olds again
One-Year Olds Again mean by 2 s.e., how likely is it that this group was drawn from the same population?

  • One-year olds know the surface sound patterns of the language

  • One-year olds do not yet know which sounds are used contrastively in the language…

  • …and which sounds simply reflect allophonic variation

  • One-year olds need to learn contrasts


Maybe not so bad after all
Maybe not so bad after all... mean by 2 s.e., how likely is it that this group was drawn from the same population?

  • Children learn the feature contrasts of their language

  • Children may learn gradually, adding features over the course of development

  • Phonetic knowledge does not entailphonological knowledge

Roman Jakobson, 1896-1982


Werker et al 2002
Werker et al. 2002 mean by 2 s.e., how likely is it that this group was drawn from the same population?

14 months

17 months

20 months

14

17

20

60

300

600

0


Swingley aslin 2002
Swingley & Aslin, 2002 mean by 2 s.e., how likely is it that this group was drawn from the same population?

  • 14-month olds did recognize mispronunciations of familiar words

Dan Swingley, UPenn


Alternatives to reviving jakobson
Alternatives to Reviving Jakobson mean by 2 s.e., how likely is it that this group was drawn from the same population?

  • Word-learning is very hard for younger children, so detail is initially missed when they first learn words

  • Many exposures are needed to learn detailed word forms at early stages of word-learning

  • Success on the Werker/Stager task seems to be related to the vocabulary spurt, rapid growth in vocabulary after ~50 words


Questions about development

Questions about Development mean by 2 s.e., how likely is it that this group was drawn from the same population?


6 12 months what changes
6-12 Months: What Changes? mean by 2 s.e., how likely is it that this group was drawn from the same population?


Structure changing
Structure Changing mean by 2 s.e., how likely is it that this group was drawn from the same population?

Patricia KuhlU. of Washington


Structure adding
Structure Adding mean by 2 s.e., how likely is it that this group was drawn from the same population?

  • Evidence for Structure Adding(i) Some discrimination retained when sounds presented close together (e.g. Hindi d-D contrast)(ii) Discrimination abilities better when people hear sounds as non-speech(iii) Adults do better than 1-year olds on some sound contrasts

  • Evidence for Structure Changing(i) No evidence of preserved non-native category boundaries in vowel perception


Sources of evidence
Sources of Evidence mean by 2 s.e., how likely is it that this group was drawn from the same population?

  • Structure-changing: mostly from vowels

  • Structure-adding: mostly from consonants

  • Conjecture: structure-adding is correct in domains where there are natural articulatory (or acoustic) boundaries [cf. Phillips 2001, Cogn. Sci., 25, 711-731]


So how do infants learn
So how do infants learn…? mean by 2 s.e., how likely is it that this group was drawn from the same population?

  • Surface phonetic patterns

  • Tests of experimentally induced changes…


5 hours’ exposure to Mandarin mean by 2 s.e., how likely is it that this group was drawn from the same population?

± human interaction

Alveo-palatal affricate vs. fricative contrast

[2003, Proceedings of the National Academy of Sciences]


Alveo-palatals mean by 2 s.e., how likely is it that this group was drawn from the same population?

affricate

fricative


Jessica Maye, mean by 2 s.e., how likely is it that this group was drawn from the same population?Northwestern U.


  • Infants at age 6-8 months are still ‘universal listeners’, cf. Pegg & Werker (1997)

  • Infants trained on bi-modal distribution show ‘novelty preference’ for test sequence with fully alternating sequence

  • How could the proposal scale up?


p listeners’, cf. Pegg & Werker (1997)(a) = p(b)

p(a) = 2 x p(b)


1.0 listeners’, cf. Pegg & Werker (1997)

.5

.25

.1


Invariance listeners’, cf. Pegg & Werker (1997)

(Jusczyk 1997)


Training on [g-k] or [d-t], generalization across place of articulation.(Dis-)habituation paradigm.

[Maye & Weiss, 2003]


So how do infants learn1
So how do infants learn…? articulation.

  • Phoneme categories and alternations

    • Perhaps more like a phonologist than like a LING101 student - look directly for systematic relations among phones

    • Gradual articulation of contrastive information encoded in lexical entries

    • Much remains to be understood


Abstraction in infant speech encoding
Abstraction in Infant Speech Encoding articulation.

  • From a very early age infants show great sensitivity to speech sounds, possibly already with some ‘category-like’ structure

  • Although native-like sensitivity develops early (< 1 year), this should be distinguished from adult-like knowledge of the sound system of the language

    • Children still need to learn how to efficiently encode words (phoneme inventory)

    • Children presumably still need to learn how to map stored word forms onto pronunciations (phonological system of the language)

  • Popular distributional approaches to learning the sound system address rather non-abstract encodings of sounds, at best


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