Speech Perception

Question 1

The challenges of speech perception

Answer 1

No clear gaps between words
accent, gender, speaking rate
time constraints - we hear up to 200 words per min

Question 2

The speech chain

Answer 2

Linguistic level - Physiological level - acoustic level - physiological level - linguistic level

Question 3

How do we produce speech?

Answer 3

lungs push air up the trachea
which vibrates the vocal chords in the larynx (voice box)
Sounds from the vocal chords are then shaped by the supralaryngeal vocal tract:
- pharynx
- oral cavity
- nasal cavity

Question 4

Speech as sound waves

Answer 4

• a periodic displacement of air molecules, creating increases and decreases in air pressure

Question 5

Source filter theory

Answer 5

Source: air vibrates vocal chords
Filter: shaped by supralaryngeal vocal tract
makes speech intelligible
Filtering appears as bands of energy at certain frequencies called formants

Question 6

Acoustic cues to consonants

Answer 6

A stop consonant is characterised by a release burst of energy followed by silence.
Voice onset time: duration of silence between release burst and vibration of vocal chords determines whether consonant is perceived as b or p.

Question 7

Acoustic cues to vowels

Answer 7

Changing from high to low vowels - F1 frequency increases. Changing from front to back vowels - F2 frequency decreases

Question 8

How do we perceive phonemes?

Answer 8

Categorical perception: the tendency to perceive gradual sensory changes in discrete fashion
Yanny/Laurel example

Question 9

The lack of invariance problem

Answer 9

the relationship between the acoustic signal and phonemes is messy
integrating information from different cues my increase detection of consistent patterns.

Question 10

Context influences speech perception

Answer 10

Visual context ‘McGurk effect”.

Prior knowledge of speech content improves intelligibility of degraded speech

Question 11

Brain basis of speech perception: classical model

Answer 11

Superior temporal gyrus for speech perception (wernicke’s area)
Inferior frontal gyrus for speech production (broca’s area)
Left hemisphere dominant

Question 12

Ventral and Dorsal Streams

Answer 12

Ventral steam for mapping speech sounds onto lexical representations
- activated for tasks focussing on comprehension
bilateral (left and right hemispheres)

Dorsal stream for mapping speech sounds onto articulatory representations
- activated for tasks focusing on perception of speech sounds
left hemisphere dominant
Broca’s area part of the dorsal stream

Question 13

fMRI- ventral and dorsal streams

Answer 13

evidence from fMRI
Dorsal stream task - repetition of nonsense words
Ventral stream task:
Listening to words

Question 14

Cohort model

Answer 14

Uniqueness point (UP): time point in the speech signal when only one word becomes consistent with the speech unit
Words are activated immediately upon minimal input
Multiple words are activated
Words compete for recognition

Question 15

TRACE model

Answer 15

information processing takes place through excitatory and inhibitory interactions.

Question 16

Ganong effect

Answer 16

Localises to the superior temporal gyrus

Question 17

Motor theory of speech perception

Answer 17

speech perception is the result of a specialised speech module that operates separately from the mechanisms involved in perceiving non-speech sounds and is uniquely human  
the objects of speech perception are intended articulatory events rather than acoustic events
complex mapping between acoustics and phonemes