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Biomedical subjects

K Wexler

Publications and source records attributed to K Wexler.

4 recordsLinked to original sources
PubMed1995

Specific language impairment as a period of extended optional infinitive.

English-speaking children with specific language impairment (SLI) are known to have particular difficulty with the acquisition of grammatical morphemes that carry tense and agreement features, such as the past tense -ed and third-person singular present -s. In this study, an Extended Optional Infinitive (EOI) account of SLI is evaluated. In this account, -ed, -s, BE, and DO are regarded as finiteness markers. This model predicts that finiteness markers are omitted for an extended period of time for nonimpaired children, and that this period will be extended for a longer time in children with SLI. At the same time, it predicts that if finiteness markers are present, they will be used correctly. These predictions are tested in this study. Subjects were 18 5-year-old children with SLI with expressive and receptive language deficits and two comparison groups of children developing language normally: 22 CA-equivalent (5N) and 20 younger, MLU-equivalent children (3N). It was found that the children with SLI used nonfinite forms of lexical verbs, or omitted BE and DO, more frequently than children in the 5N and 3N groups. At the same time, like the normally developing children, when the children with SLI marked finiteness, they did so appropriately. Most strikingly, the SLI group was highly accurate in marking agreement on BE and DO forms. The findings are discussed in terms of the predictions of the EOI model, in comparison to other models of the grammatical limitations of children with SLI.

Child↗
PubMed1990

Innateness and maturation in linguistic development.

Language is species-specific, species-wide, and highly structured. Its principles (Universal Grammar) are innate (genetically determined) in the child, although some linguistic capacity is subject to a maturational schedule, examples of which are given. Some particular aspects of language are learned, in a way driven by Universal Grammar. However, empiricist "learning theories" of all types are far too weak to be useful in explaining either the final adult language or the precise timing of developmental processes. The assumption of Universal Grammar is, in fact, crucial in explaining what kind of learning actually takes place.

Child Language↗
PubMed1986

Allele frequency distribution of two highly polymorphic DNA sequences in three ethnic groups and its application to the determination of paternity.

The allele frequency distribution of two highly polymorphic DNA sequences has been determined in three ethnic groups (American blacks, Caucasoids, and Hispanics) from the New York metropolitan area. The two loci examined were D14S1 and the flanking region of HRAS-1. The former was analyzed in EcoRI-digested DNA and the latter in TaqI-digested DNA. Approximately 700 DNA samples from unrelated individuals were digested with each of these enzymes and hybridized with the appropriate recombinant DNA probes. The size range of the DNA fragments detected for the D14S1 polymorphism varied from 14.3 to 32.5 kilobase pairs (kbp). The number of alleles identified under the experimental conditions used in this study was more than 40. For the HRAS-1 polymorphism, we have detected 18 different alleles varying in size from 1.85 to 4.5 kbp. Although the number of alleles observed in the different ethnic groups examined was very similar, the relative frequency of them varied significantly. The results presented here can be used as the basis for the utilization of DNA RFLP for the purpose of identity, such as paternity determinations or the analysis of forensic material. As an example, we have compared the results of paternity cases analyzed by HLA typing with those obtained with these two DNA polymorphisms. The values of paternity index and power of exclusion were similar by both procedures.

Alleles↗