Abstract
This study investigated the hypothesis of selective impairment on form and meaning in language processing on individuals with Williams Syndrome. It has been known that individuals with WS have spared grammatical knowledge even with mental retardation (average IQ of 55 or below) and poor cognition. Past research also showed that individuals with WS preserved normal verbal working memory and such intact verbal ability was thought to be responsible for their relatively good language performance (Wang & Bellugi, 1994; Jerrold, Baddely, & Hewes, 1999; Vicari, Brizzolara, Carlesimo, Pezzini, & Volterra, 1996; Vicari, Carlesimo, Brizzolara, and Pezzini, 1996; Karmiloff-Smith, Grant, Berthoud, Davies, Howlin, & Udwin, 1997; Robinson, Mervis, & Robinson, 2003; Laing, E., Grant, J., Thomas, M. S .C. & Karmiloff-Smith, A., in press). With a good verbal memory but deficit cognitive ability, individuals with WS are hypothesized to rely heavily on memory abilities in learning their language. This may explain the finding that grammatical knowledge of WS individuals is strong while their semantic understanding might be weak (Zukowski, 2001; Grant, Valian, & Karmiloff-Smith, 2002). In other words, individuals with WS might have selective impairment on form and meaning in their linguistic ability. In order to examine this issue, three projects were involved. The first was studying on counterfactual conditions with negation in Chinese. Counterfactuals, which are mismatched in form expression and meaning understanding, served as the ideal probes to test this hypothesis. The second project was still on counterfactuals, but with a clearer conditional marker yaobushi in sentence initial position. In doing so, it was claimed that the unambiguous reading of counterfactuals might cause more efficient process in individuals with WS. The third project was about proposition integration in semantics. It was interested to investigate the relationship between form and meaning in memory of individuals with WS. Are they more sensitive to grammatical forms than sentence meaning? A general issue of developmental delay or deviant is also raised whenever populations with mental retardation are studied. The supporters of developmental delay argued that individuals with intellectual disabilities would show similar pattern on neuropsychological profiles to their mental age matches. They are just slow in development (Zigler & Balla, 1982; Zigler, 1969). On the other hand, the supporters of developmental deviant claimed that individuals with intellectual disabilities would show a dissimilar pattern to their mental age matches. They are different in development (Ellis & Cavalier, 1982; Ellis, 1969). In this set of studies, this general issue was also under investigation. In the study of counterfactuals with negation, the constituent comparison model in sentence verification was employed (Clark and Chase, 1972; Carpenter and Just, 1975). According to this model, the number of mental operations could be calculated. We hypothesized that people might form various possible representations mentally of a complicated sentence like counterfactuals. In this case, three representations are possibly formed in mind. Two of them were form-based representations and the other was meaning-based one. Different SOA were manipulated in sentence presentation: 0-SOA (i.e. simultaneous task) and 5-sec-SOA (i.e. delayed task). Three groups in different ages were recruited for each task from the sixth graders to college students. As for individuals with WS, the SOA was unlimited. We hypothesized that under time limitation, a form-based representation was easier to be induced. The results showed that all the three age groups were highly consistent in the performance of counterfactuals. They all formed a meaning-based representation at both SOA. However, the sixth graders showed a slightly different pattern from other two groups. Meanwhile, a clear age effect was observed. The sixth graders had slowest response latency among three groups and also erred most. Individuals with WS showed a meaning-based representation as their chronological age matches of college students and mental age matches of the sixth graders. In the study of counterfactual conditionals with yaobushi, the design and procedure were parallel to the study of counterfactual conditionals with negation. Different participants in three age groups were recruited in each task. Meanwhile, two new individuals with WS participated in this study with unlimited SOA. The results showed that all three age groups were highly consistent in forming a meaning-based representation of counterfactuals at both SOA. A clear age effect and task effect were also observed. Meanwhile, the response latency in this study was faster than the one in the study of counterfactual conditional with negation in all age groups, suggesting an unambiguous reading of counterfactuals with yaobushi were processed more efficiently and successfully. As for the individuals with WS, they also formed a meaning-based representation as their chronological age controls and mental age controls. In the study of proposition integration in semantics, the basic rationale was based on proposition entailment. A Bransford and Franks’ (1971) paradigm in memory recognition was conducted. There were different superset sentences broken down into sub-sentences with different number of propositions and presented auditorily to college students and individuals with WS. Half of the sentences were presented in the training section and the other half were presented in the recognition section. Participants were asked to make judgment of each sentence and assigned a confidence rating value to each judgment. The results showed that individuals with WS showed similar patterns as their normal controls in false positive rates. However, their means of confidence ratings were significantly higher than controls. In order to argue against the possible confound of yes-bias tendency, scrambled sentences were lumped together in recognition with the other half sentences from supersets. The results showed that individuals with WS recognized the scrambled sentences as they had never heard before and assigned very negative values as their normal controls. In conclusion, individuals with WS are developmental delay, but not deviant in nature. In these three projects, they showed similar patterns as their chronological age matches in proposition integration and also in counterfactual conditionals with yaobushi. Further, they showed a similar pattern as their mental age matches in counterfactual conditionals with negation. These results indicated that they have spared logical reasoning ability and spontaneous proposition integration in their mental model. Thus, it is concluded that individuals with WS do not have selective impairment on form and meaning in their linguistic ability.