speech perception

Question 1

state challenges of speech perception.

Answer 1

• no clear gaps between words
• single words sound different in different positions of reading a sentence.
• accent, gender and speaking rate
• time constraints

Question 2

describe the speech chain

Answer 2

speaker - motor nerves from brain to vocal muscles … sound waves … listener - ear, sensory nerves to brain.
-linguistic level-physiological level-acoustic level-physicological level-acoustic level.

Question 3

describe how we produce speech.

Answer 3

• lungs push air-up the trachea …
• which vibrates the vocal cords in the larynx…
• sounds from the vocal cords are the shaped by the supra-laryngeal vocal tract.

Question 4

name parts of the vocal tract.

Answer 4

• pharynx
• oral cavity
• nasal cavity

Question 5

define consonants.

Answer 5

consonants are produced with a constriction in the vocal tract, and are classified according to three main features: manner, voicing and place of articulation.

Question 6

define sound waves.

Answer 6

• period displacement of air molecules, creating increases and decreases in air pressure.

Question 7

what does a spectrogram graph show?

Answer 7

• shows how sound amplitude varies as a function of time and frequency.

Question 8

the faster the vibration, the … the pitch.

Answer 8

higher!

Question 9

describe the source+filter model.

Answer 9

• to make speech intelligible, vocal cord sounds need to be filtered (shaped) by the supra-laryngeal vocal tract.
• filtering appears as bands of energy at certain frequencies called ‘formants’.

Question 10

which formant frequencies are the most important for speech intelligibility?

Answer 10

F1, F2, F3.

Question 11

describe stop consonants.

Answer 11

• a stop consonant is characterised by a release burst followed by silence.
• it transitions into a vowel, the formant frequencies shift around.
• formant transitions are one cue to place articulation for stop consonants.

Question 12

what is the voice onset time (VOT)

Answer 12

• duration of silence between release burst and vibration of vocal cords, determines whether consonant perceived as “b” or “p”.

Question 13

which frequency increases when changing from high to low vowels?

Answer 13

• F1

Question 14

which frequency decreases when changing from front to back vowels.

Answer 14

• F2

Question 15

state the steps that allow us to perceive phonemes.

Answer 15

1. set up a continuum of sounds between phonemes.
2. run an identification experiment
3. run a discrimination experiment.

Question 16

define categorical perception.

Answer 16

the tendency to perceive gradual sensory changes in a discrete function.

Question 17

state the three hallmarks of categorical perception.

Answer 17

1. abrupt change in identification at phoneme boundary.
2. discrimination peak at phoneme boundary
3. discrimination predicted from identification

Question 18

describe the ‘lack of variance’ problem.

Answer 18

• categorical perception demonstrates the brains ability to categorise sounds into discrete groups of phonemes, but this is difficult to do as in the real world, the relationship between the acoustic signal and phonemes is messy (overlap).

Question 19

suggest ways of how to solve to ‘lack of variance’ problem.

Answer 19

• phonemes are cued by more than acoustic feature, and so ingratiating information from different ones may enable listeners to detect consistent patterns not possible to detect when considering any one cue alone.

Question 20

state context influences on speech perception.

Answer 20

• lexical context “ganong effect”

- visual context “McGurk effect”

Question 21

true or false: prior knowledge of speech content improves intelligibility of degraded speech.

Answer 21

true - as you know what they are going to say due to prior knowledge.

Question 22

what area of the brain is responsible for speech perception?

Answer 22

the wernickes area - STG.

Question 23

what area of the brain is responsible for speech production?

Answer 23

brocas area - inferior frontal gyrus.

Question 24

describe the role of the venture stream in speech.

Answer 24

mapping speech onto lexical representations, activated in comprehension tasks, bilateral.

Question 25

describe the role of the dorsal stream in speech.

Answer 25

mapping speech onto articulatory representations, activated for tasks focussing on perception of speech sounds, LH dominant.

Question 26

define the cohort model.

Answer 26

• ideal templates of phonemes of words, single syllable activates all words beginning with that syllable, as you go on only one word will become consistent (uniqueness point)

Question 27

give evidence for the cohort model.

Answer 27

shadowing task - listeners recognise words even before they have heard the ends of the words.

Question 28

name and describe the computational model ‘TRACE’.

Answer 28

within-layer - inhibitory connections “competitive selection”
bi-directional - excitatory connections “interactive activation”.

Question 29

name and describe the computational model ‘merge model’.

Answer 29

• argue speech perception is purely bottom-up processing

- lexical context effects are attributed to changes in decisions about phonemes.

Question 30

why is it difficult to test top-down VS bottom-up accounts using behavioural experiments.

Answer 30

as both accounts make the same prediction about listeners behaviour i..e phoneme identification should be influenced by lexical context.

Question 31

what neural area does the ganong localise?

Answer 31

localises to the STG, a region implicated in low-level auditory processing.

Question 32

identify the two components of the motor theory.

Answer 32

1. speech production is the result of a specialised speech module and is uniquely human.
2. objects of speech perception are intended articulatory events rather than acoustic events.

Question 33

give evidence for the motor theory.

Answer 33

• motor and premotor areas used in producing meaningless monosyllables are also activated when listening to them.
• TMS over premotor areas interferes with phoneme discrimination in noise but not colour discrimination.

Question 34

give evidence against motor theory.

Answer 34

• categorical perception can also be demonstrated for non-speech sounds (so not speech specific).
• with training, chinchillas show the same phoneme boundary for a ‘da’-‘ta’ continuum as humans (not unique to humans).