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Biomedical subjects

H Z Ho

Publications and source records attributed to H Z Ho.

10 recordsLinked to original sources
PubMed1991

The genetic correlation between intelligence and speed of information processing.

This study examined the contributions of genetic and environmental factors to the observed correlation between intelligence test scores and speed of information processing, based on data for same-sex adult twin pairs (age, 15-57). Verbal and performance IQ scores from the Multidimensional Abilities Battery, as well as 11 reaction-time measures derived from a battery of information-processing tasks, were available for 50 monozygotic and 32 dizygotic pairs of twins. Multivariate biometrical analyses were used to estimate genetic and environmental parameters underlying observed variances and covariances among intelligence test scores and a general speed of information-processing factor (based on a linear composite of the 11 reaction-time scores). A common-factor model with loadings on general speed of processing, verbal IQ, and performance IQ fit the data well. The common factor was influenced primarily by additive genetic effects, such that the observed relationships among the speed and IQ measures are mediated entirely by hereditary factors. There was additional specific genetic variance for Verbal IQ and specific shared-twin environmental variance for Performance IQ. However, twin similarity for general speed of processing was explained entirely by genetic factors related to intelligence. The results emphasize the importance of common, heritable, biological mechanisms underlying the speed-IQ association.

Adolescent↗
PubMed1990

Sex chromosomal abnormalities. Etiology, phenotypic expression, and the role of lyonization.

Individuals with sex chromosomal abnormalities have significantly better chances of leading normal lives than individuals with autosomal abnormalities. This is due, in part, to the role of lyonization in the genetic inactivation of X chromosomes. In contrast to earlier studies contaminated with subject ascertainment bias, prospective studies of individuals with SCA generally indicate a relatively normal profile with respect to overall intellectual capacity and psychopathology. Although some SCAs affect neuromotor, speech, language, cognitive and emotional development to some degree, it is noteworthy that none of the effects necessarily occurs and that some of the deficits are amenable to corrective intervention. Results from prospective studies also indicate significant genotype-environment interactions that can have important implications for intervention.

Dosage Compensation, Genetic↗
PubMed1988

A twin study of Bannatyne's "genetic dyslexic" subtype.

Bannatyne's proposed "genetic dyslexic" subtype of reading disability (RD) was evaluated using data obtained from 60 (30 monozygotic and 30 dizygotic) pairs of affected twins (in which at least one member of each pair has a reading disorder) and 60 pairs of control twins. The predicted spatial greater than conceptual greater than sequential pattern of means was found to be reliable and specific to the RD sample. While this study does not provide conclusive evidence on the genetic etiology of the proposed subtype, our results do indicate that individuals with this particular profile may constitute a specific subtype of reading disability.

Adolescent↗
PubMed1988

Cognitive resemblance in reading-disabled twins.

This study examined the cognitive abilities of 60 pairs of reading-disabled twins aged between eight and 18 years (at least one member of each twin pair had been diagnosed as having a reading disability). Principal component analysis of nine cognitive tests yielded three readily interpretable composites of cognitive abilities--reading, symbol-processing speed and sequential memory. Scores on these three cognitive composites were significantly lower for the disabled readers than for normal readers. Individual differences in these cognitive composites within the reading-disabled twin sample were found to be due to genetic differences. Furthermore, deficits in the reading composite for the reading-disabled sample appear to be heritable.

Adolescent↗
PubMed1988

The fragile-X syndrome.

The variability in behavioral manifestations of the fragile-X syndrome and the lack of a well-defined psychological profile require the attention of behavioral geneticists and other behavioral scientists. The association with autism suggests that the fra(X) may be responsible for a genetic subtype of autism. While the fragile-X syndrome is considered an X-linked disorder, several aspects of observed transmission patterns do not follow those of classical X-linked inheritance. In particular, the finding of genetic transmission via intellectually normal males is surprising and has important implications for genetic counseling, as well as for genetic models of the fragile-X syndrome. Reports on folic acid treatment are encouraging, but not conclusive. The mechanisms involved in the association between the fra(X) chromosome and its particular phenotype are still unknown. Current investigations applying advanced techniques in molecular biology are likely to provide insight into this unique genetic disorder.

Fragile X Syndrome↗
PubMed1986

Effects of menstrual cycle on spatial information-processes.

The present study examined effects of menstrual cycle (i.e., ovulatory vs menstrual phase) on performance on spatial information-processes. Participants included 20 spontaneously cycling women (with regular 28- to 30-day menstrual cycles) who were tested on a reaction-time task developed to assess specific spatial information-processes and the Spatial Relations subtest of the PMA battery. For the spatial information-processing task, women responded faster and applied relatively less stringent criteria in the decision process during the ovulatory phase. No effects of cycle changes were found for accuracy of performance on either of the spatial tasks. It is suggested that studies examining effects of menstrual cycle on spatial ability consider an information-processing approach in measuring spatial performance and an application of signal-detection theory to separate components (strategy vs aptitude) of problem solving.

Achievement↗
PubMedDate not supplied

Genotype-environment correlations for language-related abilities: implications for typical and atypical learners.

Recent behavioral genetic research has shown that genetic propensities are associated with individual differences in experiences, and thus, what may appear to be environmental effects can reflect genetic influence. This study examines passive genotype-environment correlations (GECs) for language-related abilities by comparing environment-child language associations in adoptive and nonadoptive families. The results provide evidence for the genetic mediation of the association between home environmental variables, such as the provision of toys and games, maternal involvement, and degree of intellectual/cultural orientation with children's language-related abilities. Developmental changes in passive GECs are considered, and the implications for typical and atypical learners are discussed.

Adoption↗