speech perception Flashcards
(45 cards)
1
Q
challenges of speech perception
A
- no clear gaps between words
- co-articulation: acoustic realisation on speech depends on what you’ve just said and what you are about to say > the same words can come out differently each time
also pronunciation varies from speaker to speaker, accents, etc
2
Q
how do we produce speech
A
- lungs push air up the trachea
- which vibrate the vocal cords in the larynx
- sounds from the vocal cords are then shaped by the supraryngeal vocal tract
3
Q
labial consonants
A
lips used/touch
4
Q
alveolar consonants
A
tongue touches behind teeth
5
Q
velar consonants
A
tongue toches back of mount
6
Q
stop
A
air flow stops completely
7
Q
voice
A
when you say them vocal cords vibrate
8
Q
unvoiced
A
no vibration
9
Q
fricative
A
constriction does not happen completely, friction involved
10
Q
nasal
A
airflow redirected to nasal cavity
11
Q
sound waves
A
- periodic displacement of air molecules, creating increases and decreases in air pressure
- when we plot changes of sound pressure over time
- molecules come closer or further apart - inc and decr pressure
–> forming waveforms
12
Q
spectograms
A
split sound into different frequencies at each moment
amplitude: indicated by colour
- splits info into different frequency channels - depicts info that the brain gets
13
Q
source and filter theory
A
source: the vibrations of the vocal cords
filter: superlaryngeal vocal tract structure that shapes the sound produced by the source
14
Q
source only
A
can maybe interpret whether sound is a question? or a statement.
the gender, happy or sad
15
Q
source AND filter
A
- intelligible speech
- filter (supralaryngeal vocal tract, lips, teeth) important for sounds - PHONEMES
- filtering appears as band of energy at certain frequencies in spectrograms Called FORMANTS
16
Q
lowest three formants
A
F1 F2 F3
these are important cues for identifying vowels
- brain can know which vowel it is hearing by detecting these auditory CUES
17
Q
formants for vowels
A
F1 F2 F3
18
Q
formants for consonants
A
F2 F3
19
Q
CATERGORICAL PERCEPTION
DEMONSTRATION
A
demonstrated:
continuum of sounds ‘ba’
one end: one sound
other end: another sound ‘da’
middle: sound that is ambiguous between the two cues
- task: where they heard each sound
1st signature of categorical perception = PHONEME BOUNDARY - where ps are equally likely to respond ba as da
20
Q
1st signature of categorical perception
A
Phoneme boundary: where participants are equally likely to respond ‘ba’ than ‘da’
21
Q
2nd signature of categorical perception
A
- discrimination peak near the phoning boundary
22
Q
CATEGORICAL PERCEPTION
A
the tendency to perceive gradual sensory changes in a discrete fashion
23
Q
3 hallmarks of categorical perception
A
- abrupt change in identification at phoneme boundary
- discrimination peak at phoneme boundary
- discrimination predicted from identification (only sound ‘different’ if different phoneme
24
Q
context affects
A
- speech perception depends on prior knowledge and contexts
‘McGurk effect’: lipreading with different sound - what we hear is changed by what we see
25
McGurk effect
'McGurk effect': lipreading with different sound - what we hear is changed by what we see
26
Ganong effect
- continuum paradigm
- use the same sound but tell people its 'giss' to 'kiss' or 'gift' to ' kift'
bias to k and g changes for the one that is the real word
27
motor theory of speech perception
LIBERMAN
Component 1
- speech perception = result of specialised speech module that operates separately from the mechanisms involved in perceived non-speech sounds
AND is UNIQUELY HUMAN
EVIDENCE: Speech and not other sounds are perceived categorically e.g. yanny OR laurel - not both
basically be proven wrong
28
motor theory of speech perception
LIBERMAN
Component 2
- The objects of speech perception are intended articulatory events rather than acoustic events
EVIDENCE: speech sounds are highly variable
we are interpreting gestures rather than sounds
may still be right
29
motor theory fMRI evidence FOR
task: listen to meaningless monosyllables
outcome: auditory cortex activated (audio is being processed)
BUT
motor and premotor areas are also activated which is evidence for us interpreting sound gesturally
30
motor theory TMS evidence FOR
- TMS over premotor areas interferes with phoneme discrimination in noise but not colour discrimination
MOTOR AREAS ARE CAUSALLY INVOLVED IN SPEECH PERCEPTION
31
motor theory evidence AGAINST
- categorical perception can also be demonstrated for non-speech sounds (e.g. musical intervals)
> so not a result of a specialised speech module
- with training chinchillas show the same phoneme boundary for da/ta continuum as humans > not uniquely human
32
classic model of brain basis of speech perception
- superior temporal gyrus for speech perception (Wernicke's area)
- inferior frontal gyrus for speech production (Broca's area)
- left hemisphere dominant
33
more up to date model of brain basis of speech perception: dorsal and ventral streams
- 2 streams for speech processing that are engaged in a task dependent manner
dorsal stream: mapping speech sounds onto articulatory representations - activated for tasks focusing on perception of speech sounds - e.g. phoneme perception
ventral stream:
mapping speech sounds onto lexical representations - activated for tasks focussing on comprehension e.g. word recognition
- can explain why some aphasics can't tell apart phonemes but can recognise words and vice versa
34
dorsal stream - brain basis or speech perception
- mapping speech sounds onto articulatory representations
- activated for tasks focusing on perception of speech sounds - e.g. phoneme perception
- left hemisphere dominant
- Broca's area = involved in perception NOT JUST PRODUCTION
35
ventral stream - brain basis or speech perception
- mapping speech sounds onto lexical representations
- activated for tasks focussing on comprehension e.g. word recognition
- bilateral - left AND right hemispheres
36
evidence for ventral stream processing
- anterior temporal damage associated with semantic impairment (ventral)
inferior temporal damage associated with comprehension deficits (ventral)
37
evidence for dorsal stream processing
- listening to syllables activates motor and premotor areas (dorsal)
- TMS over premotor areas interferes with phoneme discrimination in noise but nor colour discrimination (dorsal)
38
process of recognising spoken words: cohort model
- set of word representations in your mind - what words should sound like - lexicum
- if you hear 'c' all words in lexicum that start with the sound 'c'
- as time goes on and you hear more and more of the word - less potential words are activated
until... UNIQUENESS POINT:
time-point in the speech when inly one word become consistent with the speech input > word is recognised at UP even before whole word is produced
39
uniqueness point
time-point in the speech when inly one word become consistent with the speech input > word is recognised at UP even before whole word is produced = optimal efficiency
40
key features of cohort model
- words are activated immediately upon minimal input
- multiple words are activated
- words compete for recognition - lexical competition
41
cohort model: evidence from shadowing task
- average response latency was 250ms
- average duration of words was 375ms
- recognising at uniqueness point
42
limitations of cohort model
- verbal model
- so hard to evaluate
- solution: a computer model
43
TRACE computer model of speech perception
words
phonemes
acoustic features
- connections between levels are bi-directional and excitatory (TOP-DOWN EFFECTS)
- connections within levels are inhibitory producing competition between alternatives
44
TRACE model from eye tracking
- task: take one item and move it to a different location
as more of spoken word of object is revealed, the more they start to look at the object and even rhyming/similar named objects
can put this into a computer - similar results mean human trials are doing a good job at modelling dynamics
45
TRACE and context
for the gift kiss kift giss
- if you hear a sound in context of the rest of the word - you are biased to that because you recognise it thats why if told ist- gist is preferred and i told -iss kiss is preferred
