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Biomedical subjects

S Hershberger

Publications and source records attributed to S Hershberger.

7 recordsLinked to original sources
PubMed2000

Acquisition of irregular past tense by children with specific language impairment.

In this paper we add to what is known about the tense-marking limitations of children with specific language impairment (SLI) by exploring the acquisition of regular and irregular past tense, encompassing the age range of 2;6 to 8;9 (years;months) and comparing the performance of 21 children with SLI to that of 23 control children of the same age and 20 younger control children of equivalent mean length of utterance (MLU) at the outset. The analysis differentiated between the morphophonological component of past tense marking and the morphosyntactic component (finiteness). In the morphosyntactic component, the performance of the SLI group trails that of the two control groups over 3.5 years, whereas in the morphophonological component, the SLI group's performance is equivalent to that of the younger controls. Models of growth curves for regular past tense and irregular finiteness marking show the same pattern, with linear and quadratic components and the child's MLU at the outset as the only predictor. For morphophonological growth the picture changes, with an interaction of linear trend and MLU and the child's receptive vocabulary emerging as a predictor. The findings support a morphosyntactic model, such as the extended optional infinitive (EOI) model, with regard to the limitations in finiteness marking and for affected children.

Child↗
PubMed1999

Simple and choice reaction time performance in SIV-infected rhesus macaques.

It is well established that HIV infection can lead to motor/cognitive disorders in humans. A number of studies have shown that simian immunodeficiency virus (SIV) infection in rhesus macaques parallels many aspects of HIV disease in humans. The purpose of this study was to define further the SIV-infected rhesus macaque as a model of neuro-AIDS. Our objective was to detect movement-related impairments in behaviorally trained, SIV-infected macaques using both simple and choice reaction time tasks. Reaction times (RTs), movement times (MTs), and error types were examined. Nine monkeys were infected with neurovirulent strains of SIVmac, four of which served initially as controls before their inoculation. Seven of the nine monkeys developed simian AIDS within 4 months of inoculation (rapid progressors), while two monkeys survived for more than 1 year postinoculation (slow progressors). Of the rapid progressors, four exhibited slowed reaction times and six showed movement time slowing. One rapid progressor showed evidence of a strategy shift to overcome impaired motor abilities. Monkeys with rapidly progressing SIV-related disease consistently show behavioral abnormalities reflecting underlying neuronal injury. Although the slow progressors also showed RT and/or MT slowing, a role for nonspecific factors related to late-stage simian AIDS could not be ruled out in these cases. The results demonstrate that motor impairments associated with SIV infection in rhesus macaques can be detected using RT and MT measures, further establishing the SIVmac-infected macaque monkey as a viable model of neuro-AIDS.

Animals↗
PubMed1999

The relation between sexual orientation and penile size.

The relation between sexual orientation and penile dimensions in a large sample of men was studied. Subjects were 5122 men interviewed by the Kinsey Institute for Research in Sex, Gender, and Reproduction from 1938 to 1963. They were dichotomously classified as either homosexual (n = 935) or heterosexual (n = 4187). Penile dimensions were assessed using five measures of penile length and circumference from Kinsey's original protocol. On all five measures, homosexual men reported larger penises than did heterosexual men. Explanations for these differences are discussed, including the possibility that these findings provide additional evidence that variations in prenatal hormonal levels (or other biological mechanisms affecting reproductive structures) affect sexual orientation development.

Adult↗
PubMed1999

Genetic and environmental influences on individual differences in masculinity, femininity, and gender diagnosticity: analyzing data from a classic twin study.

Analyzing data from Loehlin and Nichols's (1976) classic twin study, we computed measures of Masculine Instrumentality (M), Feminine Expressiveness (F), and Gender Diagnosticity (GD). Quantitative genetic modeling analyses of within-sex individual differences in M, F, and GD indicated that: (1) Additive genetic factors contribute significantly to individual differences in M, F, and GD. (2) The environmental effects on M, F, and GD tend to be nonshared. (3) The genetic and environmental components of individual differences in M, F, and GD tend not to show gender differences. Finally, (4) the estimated within-sex heritability of GD (.53) is significantly greater than the estimated within-sex heritabilities of either M (.36) or F (.38).

Adult↗
PubMed1998

Tense over time: the longitudinal course of tense acquisition in children with specific language impairment.

Tense marking in English is relatively late appearing and is especially late for children with Specific Language Impairment (SLI). Little is known about the full course of acquisition for this set of morphemes. Because tense marking is a fundamental property of clause construction, it is central to current theories of morphosyntax and language acquisition. A longitudinal study is reported that encompasses the years of 2;6-8;9 years for typically developing children (N = 43) and 4;6-8;8 years for children with SLI (N = 21). The findings show that a diverse set of morphemes share the property of tense marking; that this set is not mastered until age 4 years in typically developing children and after 7 years for children with SLI; that acquisition shows linear and nonlinear components for both groups, in a typical S-shaped curve; and that nonsyntactic measures are not predictors of growth (including nonverbal intelligence, vocabulary size, and mother's education), whereas initial MLU does predict rate of acquisition. The findings are consistent with a model of Optional Infinitives (OI) for typically developing children (cf. Wexler, 1994, 1996) and Extended Optional Infinitives (EOI) for children with SLI. This model hypothesizes incomplete specification of features of tense that are represented in the grammar.

Child↗