Lecture 17: Introduction to Speech Perception

Question 1

Why is speech perception challenging?

Answer 1

• Speech lacks clear gaps between words.
• Pronunciation varies due to co-articulation, accents, gender, and speaking rate.

Question 2

What is the “Now-or-Never Bottleneck”?

Answer 2

• Speech processing is constrained by its fleeting nature, requiring rapid interpretation.

Study: Christiansen & Chater (2016).
Methodology: Theoretical framework from Behavioral and Brain Sciences.

Question 3

What are phonemes?

Answer 3

• Phonemes are the smallest units of sound that convey meaning.

Example: /p/ in “pin” vs. /b/ in “bin.”

Question 4

How do phonemes differ from letters?

Answer 4

Phonemes represent sounds, not spellings (e.g., /k/ in “cat” and “kite”).

Question 5

What are the two components of the source-filter theory?

Answer 5

1. Source: Vocal cords produce sound waves (pitch and intonation).
2. Filter: Vocal tract shapes the sound into speech.

Question 6

How are speech sounds visualized in a spectrogram?

Answer 6

• Spectrograms display amplitude across time and frequency.

Formants: Bands of energy shaped by the vocal tract, critical for understanding vowels and consonants.

Question 7

What do F1 and F2 formants indicate?

Answer 7

• F1: Increases for low vowels (e.g., “hod”).
• F2: Decreases for back vowels (e.g., “heed” vs. “had”).

Study Reference: Ladefoged & Johnson (2015), A Course in Phonetics.

Question 8

What is categorical perception?

Answer 8

Gradual sensory changes are perceived as discrete categories (e.g., /ba/ vs. /da/).

Question 9

What are the hallmarks of categorical perception?

Answer 9

• Abrupt change at phoneme boundaries.
• Discrimination peaks at the boundary.
• Sounds in the same category are harder to distinguish.

Question 10

How is categorical perception studied?

Answer 10

• Identification Task: Participants label sounds (e.g., /ba/ or /da/).
• Discrimination Task: Participants indicate if two sounds differ.

Methodology: Experiments using a continuum of sounds between two phonemes.

Question 11

What real-world phenomenon illustrates categorical perception?

Answer 11

The “Yanny or Laurel” auditory illusion demonstrates categorical perception.

Question 12

What is the McGurk Effect?

Answer 12

• Visual speech (e.g., lip movements) alters auditory perception.

Example: Hearing /da/ when audio says /ba/ but lips say /ga/.

Study: McGurk & MacDonald (1976).
Methodology: Behavioral experiment using conflicting audio and visual inputs.

Question 13

What is the Ganong Effect?

Answer 13

• Lexical knowledge biases perception of ambiguous phonemes (e.g., “gift” vs. “kift”).

Study: Ganong (1980).
Methodology: Tested ambiguous phoneme boundaries with lexical context influence.

Question 14

How does auditory context affect perception?

Answer 14

Perception of ambiguous sounds (e.g., “green needle” vs. “brainstorm”) changes based on prior auditory or visual cues.

Question 15

What does the source-filter theory explain?

Answer 15

Speech production involves a sound source (vocal cords) and a filter (vocal tract), each shaping perception.

Question 16

How do categorical perception and context influence speech understanding?

Answer 16

Speech sounds are perceived categorically, and visual, lexical, and auditory contexts shape perception.

Question 17

Why is variability in pronunciation a challenge for speech perception?

Answer 17

Co-articulation, accents, speaking rate, and gender introduce variability, making consistent speech processing difficult.

Question 18

What is the role of consonant transitions in speech perception?

Answer 18

• Formant transitions, particularly F2 and F3, help identify consonants like /b/, /d/, and /g/.

Study Reference: Ladefoged & Johnson (2015), A Course in Phonetics.

Question 19

Why does discrimination peak at phoneme boundaries?

Answer 19

• Listeners are better at distinguishing sounds when they belong to different categories, even if acoustically similar.

Methodology: Identification and discrimination tasks using phoneme continua.

Question 20

How do contextual cues support speech perception in noisy environments?

Answer 20

Contextual cues (visual, lexical, or auditory) compensate for degraded or missing auditory signals, aiding comprehension.