Speech Perception Flashcards
Give 3 challenges of speech perception
- No clear gaps between words
- Co-articulation
- Accent, gender and speaking rate vary
- Time constraints; ‘now-or-never bottleneck’
What order does air travel in to produce speech?
- Lungs
- Trachea
- Larynx
- Supralaryngeal vocal tract
What is the supralaryngeal vocal tract made up of?
- Pharynx
- Oral cavity (+ lips, tongue, teeth)
- Nasal cavity
What is the purpose of the supralarygeal vocal tract?
To shape sounds from the vocal cords
What does a constriction in the vocal tract produce??
Consonants
What 3 main features are consonants classified according to?
- Manner
- Voicing
- Place of articulation
What are the 3 places of articulation?
- Labial
- Alveolar
- Velar
What are 3 examples of consonants produced from the labial place of articulation?
/b/, /p/, /v/, /f/, /m/
What are 3 examples of consonants produced from the alveolar place of articulation?
/d/, /t/, /z/, /s/, /n/
What are 3 examples of consonants produced from the velar place of articulation?
/g/, /k/, /η/
What are the 3 types of manner in consonant production?
- Stop
- Fricative
- Nasal
Define sound waves
Periodic displacement of air molecules, creating increases and decreases in air pressure
What is amplitude related to?
Loudness
What is period related to?
Inversely related to frequency
What feature of sound waves is an important cue for pitch?
Period (frequency)
What is used to analyse the frequencies of speech?
Spectogram
What is a spectogram?
Graph showing how sound amplitude varies as a function of time and frequency
Why is a spectogram useful?
The ears split sound by frequency, so spectrogram better captures the information available to the brain
What is the ‘source’ in speech production?
The larynx
What is the ‘filter’ in speech production?
Supralarygeal vocal tract
What is the source important for?
Voice pitch and intonation
What is the filter important for?
Producing different phonemes (speech sounds)
Filtering appears as ‘formants’; what are these?
Bands of energy at certain frequencies
Which 3 formants are the most important cues for speech intelligibility?
The three lowest frequencies (F1, F2, F3)
What type of vowel change decreases F2 frequency?
Changing from front to back vowels
What type of vowel change increases F1 frequency?
Changing from high to low vowels
Which 2 formants are important cues for identifying consonants?
F2 and F3
What are the 3 stages of phoneme perception?
- Continuum of sounds between 2 phonemes
- Identification experiment
- Discrimination experiment
Define categorical perception
The tendency to perceive gradual sensory changes in a discrete fashion
What are the 3 hallmarks of categorical pereption?
- Abrupt change in identification at phoneme boundary
- Discrimination peak at phoneme boundary
- Discrimination predicted from identification (they only sound different if they are different phonemes)
What concept is ‘Yanny vs Laurel’ an example of?
Categorical perception
What is the McGurk illusion an example of?
Visual context influencing speech perception
What is the Ganong effect an example of?
Lexical context influencing speech perception
How does source theory describe speech production?
Two separate components with distinct perceptual correlates
Liberman suggested that speech perception is the result of specialised speech module; what evidence did he point to?
Speech, not other sounds, is perceived categorically
Liberman suggested that the objects of speech perception are intended articulatory events; what evidence did he point to?
Speech sounds are more variable than articulations
Wilson et al (2004) found fMRI support for the motor theory of speech perception; what did they find?
Passive listening to meaningless monosyllables activates the auditory cortex, and motor/premotor areas
Meister et al. (2007) found TMS evidence for the motor theory of speech perception; what did they find?
TMS over premotor areas interferes with phoneme discrimination in noise but does not interfere in colour discrimination
How did Burns and Ward (1978) criticise motor theory of speech production? - hint: music
Categorical perception has been demonstrated for non-speech sounds, such as musical intervals
How did Kuhl and Miller (1978) criticise the motor theory of speech production? - hint: chinchillas
When trained, chinchillas showed the same phoneme boundary for /da/-/ta/ continuum as humans
What area is the superior temporal gyrus?
Wernicke’s area
What area is the inferior frontal gyrus?
Broca’s area
What brain hemisphere does the classic model of speech perception propose is dominant?
Left hemisphere
How are are the two streams for speech processing engaged?
In a task-dependent manner
Which stream is involved in mapping speech sounds onto articulatory representations?
Dorsal stream
Which stream is involved in mapping speech sounds onto lexical representations?
Ventral stream
What stream do tasks focusing on the perception of speech (e.g. phoneme discrimination) activate?
Dorsal stream
What stream do tasks focusing on comprehension (e.g. word recognition) activate?
Ventral stream
Which stream is bilateral?
Ventral stream
What did Williams et al (2005) find in support of ventral stream processing?
Anterior temporal damage associated with semantic impairment
What did Bates et al (2003) find in support of ventral stream processing?
Inferior temporal damage associated with comprehension details
What did Wilson et al (2004) find in support of dorsal stream processing?
Listening to syllables activates motor and premotor areas
What did Meister et al (2007) find in support of dorsal stream processing?
TMS over premotor areas interferes with phoneme discrimination but not colour discrimination
What 2 theories of speech perception could Meister et al (2007) be used in support for?
- Motor theory of speech processing
- Dorsal stream processing
What is the ‘uniqueness point’ in the cohort model?
The time-point in the speech signal when only one word becomes consistent with speech input, so is recognised before the entire word is heard
Give 3 key features of the cohort model of speech processing?
- Words activated immediately upon minimal input
- Activation of multiple words
- Lexical competition for recognition
What did Marslen-Wilson and Tyler (1981) find in support of the Cohort model?
Average response latency was shorter than the average word duration
How does the Cohort model suggest learning new words would affect speech processing?
Slow down recognition of new words
What is a limitation of the Cohort model?
It is a verbal model, so difficult to evaluate
What is a strength of the TRACE model?
Explains context effects, e.g. Ganong effect
How does the TRACE model explain the Ganong effect?
Word-level activity feeds back to influence lower-level phoneme activity
What are the 2 components of TRACE theory?
- Within-layer inhibitory connections for lexical competition
- Bi-directional excitatory connections between layers
