UNDERSTANDING THE PERCEPTUAL AND COGNITIVE PRECURSORS TO THE ACQUISITION OF LANGUAGE: AN EXAMINATION OF INFANTS? PERCEPTION AND USE OF MANUAL GESTURES AND SIGNS

Steven S. Robertson Barbara C. Lust Marianella CasasolaSeveral perceptual and cognitive abilities have been argued to guide language development and in particular, early word learning. This dissertation sought to determine whether these abilities extend to a signed language, like American Sign Language (ASL). A series of habituation-dishabituation experiments were conducted examining infants' ability to (1) discriminate between the visual contrasts of ASL signs and (2) form associations between words, gestures, or both paired with objects. Chapter 2 describes an experiment examining ASL-naive 6- and 10-month-olds' abilities to discriminate between the contrasts (i.e., handshape, movement, location, and facial expression) of 2-handed signs. Infants were habituated to a 2-handed sign and tested with additional 2-handed signs that varied in only one parameter. Infants detected location and facial expression changes, but did not demonstrate detection of handshape and movement changes. Similarly, Chapter 3 describes two experiments examining ASL-naive infants' abilities to discriminate between the contrasts of 1-handed ASL signs on the face. In Experiment 1, 6- and 10-month-olds' were habituated to a 1-handed sign and tested with additional 1-handed signs that varied in only one parameter. In Experiment 2, 6-month-olds were also habituated to a 1-handed sign, but were tested with 1-handed signs that varied in one or more parameters. Across both experiments, infants detected handshape and movement changes, but did not demonstrate detection of location changes. Chapter 4 describes two experiments examining 12- and 14-month-olds' ability to form associations between objects and words, gestures, or both. In Experiment 1, infants were habituated to either gesture-object or word-object pairings. In Experiment 2, infants viewed words and gestures simultaneously paired with objects. Infants were tested with a trial that maintained a pairing and a trial that violated a pairing. Fourteen-month-olds only demonstrated the ability to form associations between words and objects. Twelve-month-olds only demonstrated the ability to form associations between words and gestures simultaneously paired with objects. These findings reveal two prevalent themes. First, infants' possess general perceptual sensitivities that they can recruit for early word/sign learning tasks. Second, experience with a particular type of input (e.g., words) fine-tunes these sensitivities and abilities in a more specialized way.Ford Foundation Predoctoral Fellowship - National Academy of Science