Language DevelopmentLecture Notes: 12/2/14How is IQ measured?● Chronical Age = how old the child actually is● Mental age = age at which typically-developing children present with a certain cognitive profile○ E.g., if a child of 6 can answer a question as well as most 8 yr olds, then his/her mental age is 8● The ratio of mental age to chronological age remains constant throughout life○ E.g., 6 yr old; mental age of 8 (8/6 = 1.33)■ Same child at 9; mental age of 12 (12/9 = 1.33)● This constant ratio of mental age divided by chronological age (multiplied by 100) is called the “intelligence quotient”.○ So, if MA is equal to CA, the ratio is 1, and the IQ is 100○ If MA is higher than CA, then the ratio is greater than 1, and the IQ > 100○ If MA is lower than CA, then the ratio is less than 1, and the IQ < 100● Overall intelligence score (or intelligence quotient) is on the scale in the which the mean is 100, and the standard deviation is 15● IQ provides an overall measure of mental functioning, but may not be sufficiently fine-grained to identify all the components of cognitive ability that could underlie language development IQ scores on the Bell-Curve● Mean = 100● SD = 15● 68% of all scores fall in between 85-115Usefulness of IQ tests● Generally, fairly limited● Gold standard in diagnosing a disability (learning, language, reading, etc.)What is Intellectual Disability?● ID = significantly sub-average general intellectual functioning that is accompanied by significant limitations in adaptive functioning● Adaptive functioning = communication, self-care, home living, social skills…Why is it interesting to look at the relationship between general intelligence and language?● Because it can answer questions about modularity of language● I.e., is language just another facet of general cognitive abilities? Then, impairment in intellectual ability should result in impaired language development, and it should do so tothe same degree as the general cognition is impaired● Or, is language separable from general cognitive abilities? If so, then there should be dissociations between intellectual impairment and language developmentDown Syndrome● Chromosomal abnormality● Present in 1 out of 800 newborns● Usually accompanied by moderate to severe intellectual impairment● IQ is usually below 50● Most do not achieve typical linguistic competenceLanguage Development in Children with Down Syndrome● In general, language is more impaired than other cognitive functions● Production deficits exceed comprehension deficits● Onset of babbling and phonological development are delayed○ Phonological processes that are typical of younger children (e.g., cluster reducation) continue into adolescence or adulthood○ Difficulty producing intelligible speech● Lexical development is delayed (first word is produced around 24 months)● Grammar is particularly impaired○ Both production and comprehension of grammar are delayed relative to mental age○ Particularly likely to omit function words and verbs● May take 12 years to do what most children accomplish in 30 months● Early studies; Language development halts at 12 yrs olf (at which point, a child with Down Syndrome has a mental age of 6, and produces speech with grammatical complexity typical of a 2-3 yr old)Language Development in Children with Down Syndrome● Communicative/pragmatic skills are strong● Children with Down Syndrome vocalize and engage in mutual eye-gaze more than do typically-developing infants● But...have difficulty with joint attention● Interested in social interactions, and less interested in objects● Make for competent conversation partners● But...do not do as well on referential What does Down Syndrome tell us about the relationship between language and cognition?● On the one hand, shows the relationship between the two: Cognition is impaired → language is delayed● On the other hand, some aspects of language development are even more delayed thancognitive development● Cognition is not the only relevant factor in language development● Different components of language are affected to different degrees → more than one cognitive ability underlies languageWilliams Syndrome● Very rare genetic disorder (about 1 in 7,500 births)● IQ-wise, children with Williams Syndrome have the same level of ID as children with Down Syndrome (ranges from 40 to 70)Language Development in Children with Williams Syndrome● Early evidence○ Speak in long, grammatical sentences, use rich vocabulary, and can tell long, coherent stories○ They are almost more verbal and conversational than typically developing children○ Grammar is morphologically-correct and syntactically-complex○ Very social■ From infancy, demonstrate extreme sociability○ They spend more time looking at people’s faces than typically developing children○ Good phonological memory skills● Later Evidence○ Language is still not at the level of typically developing children○ Lexical development precedes cognitive development■ E.g., they learn words before pointing, and experience the word spurt before categorization○ Deficits in morphosyntactic knowledge○ Tell complex stories, but cannot answer questions about the stories they tell○ Difficulty with non-literal language○ The course of development and ultimate language attainment is different from typically developing childrenWhat does Williams Syndrome tell us about the relationship between language and cognition?● Striking dissociation between intellectual ability and language development● Language may not be affected by a general intellectual impairment● However, language is not completely spared, either (especially rule-based aspects of language)Definitions of SLI● Developmental language disorder● Diagnosed through exclusion of other diagnoses● I.e., Specific Language Impairment is a language impairment that is not due to○ Hearing impairment○ Cognitive impairment or Neurological dysfunction○ Autism● Accompanied by deficits in morphology and phonological memory (although articulation difficulties are also common)● Estimated to affect 5% to 20% of children● Has genetic component: 20% of family members of children with SLI also have some language impairmentEarly Signs of SLI● “Late talkers” who do not “outgrow” it● Developmental delay in all language areas, including phonology, semantics, syntax,