LECTURE 3 BOOK

Introduction

• Standard dictionary definition of language: “the particular form of speech of a group of people.”
• Cognitive neuroscience definition: “a symbolic system used to communicate concrete or abstract meanings, irrespective of the sensory modality employed or the particular means of expression.”
  • Includes spoken, written, and sign language.
• Speech and language are intensively studied due to their importance in human societies.
• Languages vary widely (6000-7000 in use), but include:
  • Vocabulary
  • Grammar
  • Syntax rules
• Written forms exist for ~200 languages.
• Animal communication systems are studied to understand language origins.

Speech

Producing Speech

• Human vocal tract: larynx to lips (Figure 12.1A).
• Air from lungs passes through the glottis (opening between vocal cords).
• Airstream acceleration causes decreased pressure, vibrating the vocal cords (Bernoulli’s principle).
• Vibration frequency determined by vocal cord tension (100-400 Hz).
• Fundamental frequency varies based on the gender and size of the speaker.
• Vocal tract shapes and filters sound, like a guitar body.
• Speech formants: peaks of power produced by source-filter mechanism (Figure 12.1B).
• Vocal tract shape is changed by muscles of the pharynx, tongue, and lips, producing different speech sounds and formant frequencies.
• Relative formant frequencies create voiced speech sounds.
• Source-filter model of speech:
  • Lungs: air reservoir
  • Diaphragm and chest muscles: motive force
  • Vocal cords: periodic vibration for voiced sounds
  • Pharynx, oral/nasal cavities: filter

Comprehending Speech

• Phones: basic speech sound stimuli.
• Phonemes: perception of phones.
• Syllables: made up of one or more phones.
• Words: syllables make up words.
• Sentences: words make up sentences.
• ~200 phones exist, with 30-100 used per language.
• Difficulty learning new languages arises from unfamiliar phones.
• Accents persist if a second language is learned after age 8 due to entrenched phoneme production/perception.
• Phones are divided into vowels and consonants.
• English has ~40 phones, nearly equally divided between vowels and consonants.
• Vowel sounds:
  • Voiced elements, generated by vocal cord oscillations.
  • Tonal qualities, eliciting pitch perception.
  • Majority of acoustic power in speech.
• Consonant sounds:
  • Begin and/or end syllables.
  • Briefer, with rapid energy changes.
  • Categorized by place/manner of articulation.
  • Click languages use double consonants made by tongue movements.
• Consonants carry the main information in speech.

Interpreting Speech Sounds

• Speech doesn't have discrete breaks between syllables or words.
• Neural processing proceeds holistically.
• Speech percepts are actively created, not just neural translations of physical stimuli.
• Eye movements during reading don't follow syllabic or word boundaries.
• Syllables and words are not natural units of speech processing.
• Alvin Liberman proposed that we perceive underlying “vocal gestures,” corresponding to vocal tract movements.
• Coarticulation: vocal-tract changes overlap in time and influence each other.
• Acoustic characteristics of phones overlap between speakers.
• Speech perception relates more to vocal intention and meaning than physical sound.

Sentences, Grammar, and Syntax

• Sentences: word sequences expressing a complete thought.
• Grammar: rules by which words are formed and combined.
• Syntax: rules describing combinations of grammatically correct words/phrases.
• Grammar and syntax change over time and vary among languages.
• English uses subject-verb-object order, but other arrangements exist.

The Importance of Context

• Phone, syllable, word, phrase, and sentence meanings are ambiguous.
• Homonyms: words with same spelling/sound but multiple meanings (e.g., bank).
• Homophones: words with same sound but different meanings/spellings (e.g., kernel/colonel).
• Understanding depends on context and experience.
• William Bagley's work showed correct syllable identification depends on immediate surroundings.
• Words are easier to recognize in sentences.
• Recognition increases with usage frequency.
• McGurk effect: what we see influences what we hear.
  • Speech sounds are influenced by seen lip/tongue movements.
  • Integration occurs in the superior temporal sulcus region.
• Speech perception is based on the empirical significance of speech sounds within a broader context.

Acquiring Speech and Language

Learning A Vocabulary

• Learning languages is a remarkable feat.
• Requires knowing word meanings (vocabulary acquisition).
• The Oxford English Dictionary includes ~500,000 words.
• Vocabulary is in constant flux, with words being lost and added.
• A highly verbal person knows ~50,000 words, but ~10,000 are used in ordinary discourse.
• Learning involves grammar/syntax, complicated by context.
• Learned through trial and error in infancy/childhood.

The Shaping of Phonemes and Phones

• Infant's perception/production of speech is shaped by heard sounds from early postnatal life.
• Languages use different subsets of ~200 phones.
• Infants can initially perceive/discriminate among all speech sounds.
• This ability diminishes, causing difficulties for older children/adults in perceiving/uttering unfamiliar phones.
• Native Japanese speakers can't reliably distinguish /r/ and /l/ in English.
• 4-month-old Japanese infants can make this discrimination.
• Infants show preferences for native language phonemes by 6 months.
• By the end of the first year, they no longer respond to non-native phonetic elements.
• “Baby talk” (motherese) emphasizes phonetic distinctions, helping infants learn.
• Losing acoustic discrimination is specific to speech sounds; adults can discriminate non-speech sounds with similar characteristics.

A Critical Period For Language Acquisition

• Ability to learn another language fluently persists for some years.
• Learning requires experience relatively early in life.
• Neural circuitry is especially susceptible to modification during early development.
• Malleability diminishes with maturation.
• The critical (sensitive) period is the window for extensive neural modification.
• Jacqueline Johnson and Elissa Newport's studies:
  • Second language acquisition in Asian Americans.
  • Learning before age 7 results in native-speaker performance.
• Effects on language skills are more marked when deafness occurs early in life.
• Brain activation differences in children/adults indicate pertinent neural regions.
• Normal acquisition is subject to a decade-long critical period.
• Some ability to learn persists into adulthood, but at a reduced level.
• Early experience is important for cognitive abilities.

Mechanisms of Language Learning

• Extensive exposure and practice are the most obvious aspects.
• Proficiency requires repeated activation of relevant neural circuits.
• Exposure/practice strengthen language-relevant circuits.
• Absence of exposure weakens connections representing non-native sounds.
• Used circuitry is retained, unused circuits weaken.
• Changes arise from neural activity influencing synaptic connections.
• Paul Bloom suggests children can