Speech Perception

Question 1

What is speech perception?

Answer 1

Mental processes that convert sounds into comprehended speech

Question 2

Articulation

Answer 2

A physical event of how we configure our vocal tract to produce sound

Question 3

Articulatory phonology theory

Answer 3

• Based on gestural score: tells articulators (lips, tongue, etc) how to move –> depends on context of the word
• Articulators move semi-independently to control air in the lungs –> contrastive gestures create change in speech patterns
• Articulator movement produces phonemes
  via place, manner, and voicing of articulation
• Phonemes produced via co-articulation (overlap with one another)

Question 4

Sound waves

Answer 4

• Compression and rarefaction of air made up into cycles –> amount of time elapsing during a cycle determines pitch (frequency) of speech & amount of energy in a sound wave determines volume (amplitude of speech
• Sound spectrogram represents pattern of acoustic energy: formants (pitches) changes size and shape of vocal tract –> speech sounds are made up of different formants and formant transitions

Question 5

Challenges in speech perception

Answer 5

• No clean breaks in speech, just a steady stream
• Co-articulation
• Variability in speech

Question 6

Motor Theory

Answer 6

• Perceiving speech = perceiving gestures
• Sound represents the fundamental unit of mental representation in speech –> motor system is recruited for speech perception
• Process of perception: register acoustic signal, determine gesture that produced it, deduce word from gestures
• ADVANTAGE: relationship between gestures and phonemes is CLOSER than the relationship between acoustic signal and phoneme
• Link between speech perception and production

Question 7

Speech perception mechanism (Fodor, 1983)

Answer 7

• Speech model: monitors and reacts strongly to complex speech characteristics; uses pre-emption; prevents spectral analysis (formant transitions perceived as linguistic when embedded in other speech sounds)
• “Chirps” and “squeaks” are perceived as linguistic features when embedded in other speech sounds
• Leads to (1) Duplex Perception and (2) Categorical Perception

Question 8

(1) Duplex Perception

Answer 8

• Perception of both spectral analysis and actual speech at the same time –> perceived as intact normal speech
• Evidence for General Purpose Auditory Processing and Specific Speech Perception Model

Question 9

(2) Categorical Perception

Answer 9

• Despite variation in the speech system, one is “blind” to many physical/acoustic differences which means we still perceive the same sounds
• Poor discrimination for two speech sounds that arise from the same category, good discrimination for two speech sounds that cross the boundary between categories
• Does not properly describe how we experience speech (speech perception is continuous)

Question 10

McGurk effect

Answer 10

non-acoustic information affects speech perception (multimodal: vision, hearing, touch)

Question 11

Mirror neurons

Answer 11

• Frontal and parietal cortex neurons activated both when a monkey performs an action and when they see another monkey perform that action
• Simulation theory (Gallese & Goldman, 1998): simulation of action in the brain is created (perceiving speech sounds causes neurons to fire) –> simulation reminds the brain of its own intentions behind an action and helps infer the intentions of another person
• Mirror neurons form after birth in response to repeated exposure and experience of seeing an action
• Neuroimaging studies show that listening to speech activates motor cortex, but depends on how speech sounds are produced

Question 12

Problems with motor theory

Answer 12

• Infants perceive speech sounds they cannot produce
• Duplex and categorical perception occur in non-speech stimuli
• Aphasia provides evidence for double dissociations between speech production and perception
• Same phonemes result from same gestures

Question 13

General Acoustic Theory/Fuzzy Logic Model

Answer 13

• Perceiving speech ≠ perceiving gestures; does NOT involve motor system
• Multiple sources of information influence speech perception –> domain general learning
• Uses top-down (favors real word over non-word) AND bottom-up (phonemic restoration) processing of continuous information
• Processes: make use of stored information and then compares to current information via (1) evaluation, (2) integration, (3) decision
• Derives from the general properties of the auditory system, looks at speech as a cue-based system that is not species-specific