Project: Research project

Project Details


DESCRIPTION: In typically-developing children initially slow, one-at-a-time
word learning is followed by an apparent explosion in their lexicon. One
estimate suggests that children are learning up to nine new words a day. By
contrast, for some individuals with severe mental retardation new words
enter the lexicon only through slow and deliberate effort. Yet word
learning is a foundational component of human development, necessary for
advanced linguistic functions and contributing to complex representational
skills (e.g., categorization). To the extent that a cognitive disability
interferes with word learning, progress in these domains will be
correspondingly limited. It is therefore essential to explore in detail the
nature of lexical impairments in severe mental retardation. The existence
of difficulties in lexical acquisition among individuals with severe mental
retardation raises important questions. When rapid vocabulary expansion
occurs, what linguistic cognitive processes support that learning? When it
does not occur, what skills are deficient or absent? A phenomenon called
fast mapping may be of greatest potential relevance for rapid vocabulary
expansion. Fast mapping refers to a quick, initial partial understanding of
a new word's meaning derived from the context of word use. Fast mapping has
been argued to facilitate the vocabulary explosion. This proposed role has
received empirical confirmation in typical youngsters and children with Down
syndrome. Yet evidence from children with atypical cognition/language has
recently challenged the universality of this relation. The Principal
Investigator's studies have added to the preliminary evidence of selective
deficits in fast mapping among individuals with severe mental retardation,
William's syndrome, or specific language impairments. The deficits are most
often observed when individuals attempt to apply the principle for the
purpose of vocabulary expansion. These recent findings oblige a more
systematic analysis of the precise role of the principle in learning
outcomes in mental retardation. Is fast mapping at risk in individuals with
severe mental retardation, potentially limiting their vocabulary expansion?
This application proposes a five-year study of vocabulary expansion and
delay, focusing specifically on rapid expansion of an extant, but limited,
vocabulary. The proposed series of studies will implement methods developed
by the Principal Investigator that will enable the systematic analysis of
unresolved questions of lexical expansion in severe mental retardation. The
project has four specific aims that will be addressed in the course of four
studies: 1) To examine the relation of fast mapping, rapid vocabulary
expansion, and nonverbal processes, in order to explore the nature of
lexical expansion in severe mental retardation; 2) To explore the points of
greatest vulnerability for learning through fast mapping by explicitly
taxing participants' skills and observing the ways in which breakdowns
occur; 3) To extend the analysis from the commonly examined object-word
learning to the acquisition of action-related words, to determine whether
processes of fast mapping are similar for the two types of form/class
categories; 4) To examine the basis underlying children's apparent
assumption that new words should and do map to unnamed objects, and whether
this assumption is intact among individuals with severe mental retardation.
Effective start/end date4/1/983/31/99


  • Eunice Kennedy Shriver National Institute of Child Health and Human Development

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