JH

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