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Lecture 10

Psych 2220A Lecture 10

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Psychology 2220A/B
Scott Mac Dougall- Shackleton

Psych 2220A Lecture 10 • Is it true only humans have language? • Evidence in non-human primates and other animals • Evolution of language • How specialized are our brains for language? • Domain-general and domain-specific mechanisms • Language disorders • Reading • How is language processed in the brain? • Wernicke-Geschwind model • Cognitive neurosciences approachLearning outcomes What is language? • Systematic and conventional use of sounds (or signs or written symbols) for the purpose of communication or self expression • Complex communication system • Intentionality • Arbitrary symbols/reference • Grammar/syntax • Cultural or social transmission •If language is unique to humans, then we are the only ones that should exhibit these behaviours/ abilities Language in non-human primates • Can acquire aspects of language • No syntax or reference • Why can’t chimpanzees acquire language? • Don’t have innate language acquisition device • Vocal limitation • Reference problem • Cultural/social transmission Are humans the only animals that exhibit these behaviours/abilities? • Complex communication system • Honey bee (apis mellifera) • Grammar/syntax andArbitrary symbols/reference in Black-capped chick-a-dee call notes • Cultural transmission: • Predisposed to learn own-species song • Abnormal song regains normal song characteristics over generations • Learned dialects • Many other animals share characteristics that we use to define human language • So what aspect of language is truly unique to humans? • If we are the only ones to exhibit language, how did this ability evolve? Psych 2220A Lecture 10 How did the brain evolve to process language? •Adaptation • New brain areas • Specialized, not shared with non-linguistic ancestors • Descent with modification • Remodeling and reuse of existing rudimentary structures • Share some similarities with non-linguistic ancestors Revising the nature-nurture debate • Language acquisition and use requires both nature and nurture • Domain-general and domain-specific theories of language differ on views of how specialized our innate learning mechanisms are: • Have we evolved specialized brain areas only for learning and processing language? • Or have we found ways to adapt our pre-existing abilities for use with language? Brains for language: specialized or coopted? • Domain-specific mechanisms • Complex cognitive abilities are supported by specialized, evolutionarily adaptive learning devices • Modularity: mind as a bundle of many special-purpose modules • Linguistic theory • Primary role of left hemisphere is language • Domain-general mechanisms • Complex cognitive abilities arise from combinations of general, basic cognitive processes • General capacities support language acquisition and use • Symbolic representation, memory, pattern analysis • Language is a secondary function of these general processes •Analytic-synthetic theory • Motor theory Examples • Domain-specific • Dual-process theory • Rule learning; Rule: past tense, add “ed” visit --> visited • Memory; Memory: irregular forms, go --> went • Domain-general • Neural networks & computational models • Decentralized interconnected network of simple units (neurons) Support for domain-specific mechanisms • Universal grammar • Language invention • Werker & Tees, 1984 Psych 2220A Lecture 10 • Innate language acquisition device • Infants show language processing skills not likely due to experience Support for domain-general mechanisms •“Why, what weekend were you guys gonna be there?” • Statistical learning; Saffran et al 1996 •Areas that are more active during singing than speaking • Singing – humming (speaking) • Shared neural networks between language and music; Besson & Schon, 2006 Language disorders • Language disorders may tell us more about domain specificity of language • Specific language impairment (SLI) • Dyslexia • Aphasia Specific language impairment (SLI) •Abnormal grammar without obvious sensory/motor impairment or IQ deficit • KE family in Birmingham: 16/30 members with severe SLI • Genetic mutation? • FOXP2 is a regulatory gene on chromosome 7 that affects transcription of a variety of other genes • Mutations at FOXP2 affect neural development and communication in other species Dyslexia • Impairment in reading without apparent visual, motor, or intelligence deficits • Developmental dyslexia • Evident when child learns to read • Surface: lexical, cannot pronounce words based on memory • Deep: phonological, cannot spell out words phonetically • Lexical knowledge is equivalent to vocabulary; phonemes are the smallest meaningful units of sounds in a language SLI & Dyslexia • Impaired innate grammar mechanism or impaired information-processing ability? • SLI: deficit in processing of rapid, sequential information, phonological salience? (Jonaisse & Seidenberg, 1998). • Developmental dyslexia may be caused by deficits in phonological awareness (and mapping) • Plasticity • Changes in behaviour can be cause or consequence of dyslexia • Differences in brain activation of beginning vs proficient readers Psych 2220A Lecture 10 Aphasia • Broca’s aphasia •Affects production • Wernicke’s aphasia •Affects comprehension Does Broca and Wernicke’s aphasia support domain-specific mechanisms? • Broca’s aphasics also have difficulty comprehending complex sentences with potential ambiguity • The apple that the boy is eating is red. • The boy that the girl is chasing is tall. • Difficulty primarily in linking disparate parts of sentences • Singing helps speech production in some patients with Broca’s aphasia Reading • Reading and writing are relatively recent inventions. • Improbable that our brains have evolved to read writing. • Visual word form area • Left midfusiform gyrus • More strongly activated when viewing words than other objects - including complex line drawings, digits, and unknown characters (Dehaene & Cohen 2011) • Localized activation reproducible across cultures, reading direction, types of script • But also activated in tasks that do not engage visual word form processing such as naming colours & pictures, repeating auditory words (Price & Devlin 2003) • Cortical recycling hypothesis: VWFAbecomes functionally specialized (but not completely specific) for words because it is competent at recognizing line configurations and junctions (Dehaene & Cohen 2011) • The debate regarding language as domain-specific or domain-general is still ongoing • Existence of disorders specific to language suggests language is special • However, many of the deficits in these disorders can also be explained by general non- language specific impairments (e.g. mapping sounds to letters in dyslexics) • Language is concretely represented in the brain • Language activates certain areas in the brain • Damage to specific language-related brain areas can cause relatively predictable language problems Does our ability for language require specialized brain area/circuits? Language processing in the brain • We will discuss two ideas of how language is processed: • Wernicke-Geschwind model • Cognitive neurosciences approach Psych 2220A Lecture 10 • Can you tell which one takes a domain-specific view and which one takes a domain-general view of language? Wernicke-Geschwind model • Serially-connected brain regions • Localization centers for perception, comprehension, production • Each region performs a specific function, thus damage to specific regions should have predictable effects Joining in on a conversation ReadingAloud Psych 2220A Lecture 10 Problems with the Wernicke-Geschwind model • Proposes localization of language perception, production, and comprehension • What is involved in these abilities? •Attention • Planning • Inhibitory processes • Long-term memory • Short-term memory • Decoding noise (e.g. variations in voice/accents or handwriting) More problems with the Wernicke- Geschwind model • Words do not have to be transformed into pseudo- auditory response • Project to Broca’s without stopping at angular gyrus • Damage or leisons resulting in aphasia are not restricted to Broca’s or Wernicke’s area • Subcortical structures • Cortical plasticity and recovery of function • Comprehension deficits in Broca’s aphasia and production deficits in Wernicke’s aphasia • Individual differences in locations of cortical language areas Mapping language-related areas • Penfield & Roberts 1959 • Electrical stimulation of different brain areas to see which ones affected language • Large individual differences • Not limited to areas in Wernicke-Geschwind model Decentralized language areas • Cognitive neuroscience approach • Small, widespread, individual variation, multiple functions •Attention • Planning • Inhibitory processes • Long-term memory • Short-term memory • Decoding noise Psych 2220A Lecture 10 • Language-like abilities and intelligence in anAfrican Grey Parrot Brain organization • Mammalian brain structure not necessary for complex cognitive processes and behaviours. Localization of function • Both Wernicke-Geschwind and cognitive neuroscience- based theories propose localization of language functions • But they disagree on the degree and specificity of l
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