acoustic continua and phonetic categories
DESCRIPTION
Acoustic Continua and Phonetic Categories. Frequency - Tones. Frequency - Tones. Frequency - Tones. Frequency - Tones. Frequency - Complex Sounds. Frequency - Complex Sounds. Frequency - Vowels. Vowels combine acoustic energy at a number of different frequencies - PowerPoint PPT PresentationTRANSCRIPT
Acoustic Continua andPhonetic Categories
Frequency - Tones
Frequency - Tones
Frequency - Tones
Frequency - Tones
Frequency - Complex Sounds
Frequency - Complex Sounds
Frequency - Vowels
• Vowels combine acoustic energy at a number of different frequencies
• Different vowels ([a], [i], [u] etc.) contain acoustic energy at different frequencies
• Listeners must perform a ‘frequency analysis’ of vowels in order to identify them(Fourier Analysis)
Frequency - Male Vowels
Frequency - Male Vowels
Frequency - Female Vowels
Frequency - Female Vowels
Synthesized Speech
•Allows for precise control of sounds•Valuable tool for investigating perception
Timing - Voicing
Voice Onset Time (VOT)
60 msec
English VOT production
• Not uniform
• 2 categories
Perceiving VOT
‘Categorical Perception’
Discrimination
Same/Different
Discrimination
Same/Different0ms 60ms
Discrimination
Same/Different0ms 60ms
Same/Different
Discrimination
Same/Different0ms 60ms
Same/Different0ms 10ms
Discrimination
Same/Different0ms 60ms
Same/Different0ms 10ms
Same/Different
Discrimination
Same/Different0ms 60ms
Same/Different0ms 10ms
Same/Different40ms 40ms
Discrimination
Same/Different0ms 60ms
Same/Different0ms 10ms
Same/Different40ms 40ms
Why is this pair difficult?
Discrimination
Same/Different0ms 60ms
Same/Different0ms 10ms
Same/Different40ms 40ms
Why is this pair difficult?
(i) Acoustically similar?
(ii) Same Category?
Discrimination
Same/Different0ms 60ms
Same/Different0ms 10ms
Same/Different40ms 40ms
Why is this pair difficult?
(i) Acoustically similar?
(ii) Same Category?
A More Systematic Test
Discrimination
Same/Different0ms 60ms
Same/Different0ms 10ms
Same/Different40ms 40ms
A More Systematic Test
0ms
20ms
40ms
20ms
40ms
60ms
Discrimination
Same/Different0ms 60ms
Same/Different0ms 10ms
Same/Different40ms 40ms
A More Systematic Test
0ms
20ms
40ms
20ms
40ms
60ms
D T
D
T T
D
Within-Category Discrimination is Hard
Cross-language Differences
R L
Cross-language Differences
R L
R L
Cross-Language Differences
English vs. Japanese R-L
Cross-Language Differences
English vs. Hindi
alveolar [d]
retroflex [D] ?
Russian-40ms
-30ms
-20ms
-10ms
0ms
10ms
Development of Speech Perception3 Classics
Development of Speech Perception
• 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
0 months 6 months 12 months 18 months
UniversalPhonetics
Native Lg.Phonetics
Native Lg.Phonology
#1 - Infant Categorical Perception
Eimas, Siqueland, Jusczyk & Vigorito, 1971
Discrimination
Same/Different0ms 60ms
Same/Different0ms 10ms
Same/Different40ms 40ms
A More Systematic Test
0ms
20ms
40ms
20ms
40ms
60ms
D T
D
T T
D
Within-Category Discrimination is Hard
English VOT Perception
To Test 2-month olds
Not so easy!
High Amplitude Sucking
Eimas et al. 1971
General Infant Abilities
• 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
Universal Listeners
• Infants may be able to discriminate all speech contrasts from the languages of the world!
How can they do this?
• Innate speech-processing capacity?
• General properties of auditory system?
What About Non-Humans?
• Chinchillas show categorical perception of voicing contrasts!
#2 - Becoming a Native Listener
Werker & Tees, 1984
When does Change Occur?
• About 10 months
Janet Werker
U. of British ColumbiaConditioned Headturn Procedure
When does Change Occur?
• Hindi and Salishcontrasts testedon English kids
Janet Werker
U. of British ColumbiaConditioned Headturn Procedure
What do Werker’s results show?
• Is this the beginning of efficient memory representations (phonological categories)?
• Are the infants learning words?
• Or something else?
#3 - What, no minimal pairs?
Stager & Werker, 1997
A Learning Theory…
• How do we find out the contrastive phonemes of a language?
• Minimal Pairs
Word Learning
• Stager &Werker 1997
‘bih’ vs. ‘dih’and‘lif’ vs. ‘neem’
Word learning results
• Exp 2 vs 4
Why Yearlings Fail on Minimal Pairs
• 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 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...
• 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
Connecting Hearing & Speaking
Connecting Hearing & Speaking
Auditory [ba] + Visual [ga] = Perceptual [da]
McGurk Effect
Connecting Hearing & Speaking
Auditory [ba] + Visual [ga] = Perceptual [da]
Evidence for connection
• Infants know connection between visual and auditory speech stimuli
• Mix and match[a] vs. [i]
Questions about Development
6-12 Months: What Changes?
Structure Changing
Patricia KuhlU. of Washington
Structure Adding
• 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
• 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
So how do infants learn…?
• Surface phonetic patterns
So how do infants learn…?
• 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
Learning Sound Patterns
• Phonological learning problem– 1 year olds know distribution of surface categories– They behave as if they know conditioned allophones because the
critical tests involve phonotactic violations– The challenge is to learn relations among surface patterns - implies
some notion of phonological similarity, e.g. t-th are related, or evidence of morphophonological alternations
– Challenge: similarity space is not straightforward, e.g., flap is an allophone of /d,t/ in English, but of /r-l/ in Korean.
– Surface patterns can be learned without knowing meanings, i.e. without a lexicon; meanings shouldn’t be necessary even for learning conditioned allophony
• So what is the connection between lexical learning and phonological encoding?
Learning the Lexicon
• Developmental change in lexical encoding– Prior to ‘vocabulary spurt’ (~50 words), lexical encoding is slow and labored -
fine detail only evident in highly familiar words
– Later, detailed lexical encoding can be handled much more efficiently
• Is this related to the learning of a phonological system?– Early difficulties in encoding could be attributed to the lack of an appropriate
phonological ‘alphabet’ for the native language
– But how can this be reconciled with the surface knowledge of sound patterns in 12-month olds?
• Do children gradually develop more efficient lexical representations as they accrue knowledge of what is predictable?