Genetic and environmental influences on individual differences in printed word recognition

The genetic and environmental etiologies of individual differences in printed word recognition and related skills were explored in 440 identical and fraternal twin pairs between 8 and 18 years of age. A theoretically driven measurement model identified five latent variables: IQ, phoneme awareness, word recognition, phonological decoding, and orthographic coding. Cholesky decomposition models on these five latent constructs revealed the existence of both common and independent genetic effects, as well as non-shared environmental influences. There was evidence for moderate genetic influences common between IQ, phoneme awareness, and word-reading skills, and for stronger IQ-independent genetic influences that were common between phoneme awareness and word-reading skills, particularly phonological decoding. Phonological and orthographic coding skills in word recognition had both significant common and significant independent genetic influences, with implications for "dual-route" and "connectionist" reading models, subtypes of reading disabilities, and the remediation of reading disabilities.     

Genetic and environmental influences on applied creativity: A reared-apart twin study

Applied creativity involves bringing innovation to real-life activities. The first reared-apart twin study assessing genetic and environmental origins of applied creativity, via Draw-a-House (DAH) and Draw-a-Person (DAP) tasks, is presented. Participants included 69 MZA and 53 DZA twin pairs from the Minnesota Study of Twins Reared Apart. Drawings were evaluated by four artists and four non-artists. Genetic effects were demonstrated for the DAP (.38–.47), but not for the DAH. Creative personality showed genetic effects (.50), and modest, but significant correlations with scores on the two drawings (rs = .17–.26). Both genetic and nonshared environmental influences underlie variance in applied creativity. Individuals concerned with enhancing creativity among students and others may better understand individual differences in performance and training.     

Genetic and environmental effects on stuttering: a twin study from Finland

The present study explored the prevalence of self-reported stuttering in a Finnish twin population and examined the extent to which the variance in liability to stuttering was attributable to genetic and environmental effects. We analyzed data of 1728 Finnish twins, born between 1961 and 1989. The participants were asked to complete a questionnaire on speech, language, and voice. In two of the questions they were asked to report the occurrence of childhood and present stuttering of their own and that of their sibling. According to the results, 2.3% (52) of the participants were reported to have stuttered as children and 28.8% of them (15) were reported to continue to stutter in adulthood. There was no significant gender difference in the prevalence of stuttering in either childhood or adulthood. For childhood stuttering, the tetrachoric correlation was higher for monozygotic pairs (r=.74) than for dizygotic pairs (r=.27). By means of structural equation modeling it was found that 82% of the variance in liability to childhood stuttering was attributable to additive genetic effects, with the remaining 18% due to non-shared environmental effects. In conclusion, the results of the present study confirm findings from prior studies and support a strong genetic and only a moderate non-shared environmental effect on stuttering. Potential small differences in the prevalence of stuttering in different populations are suggested by our data. EDUCATIONAL OBJECTIVES: The reader will be able to recognize the contribution of genetic and environmental effects on stuttering.     

Genetic and environmental influences on antisocial behavior: a meta-analysis of twin and adoption studies

A meta-analysis of 51 twin and adoption studies was conducted to estimate the magnitude of genetic and environmental influences on antisocial behavior. The best fitting model included moderate proportions of variance due to additive genetic influences (.32), nonadditive genetic influences (.09), shared environmental influences (.16), and nonshared environmental influences (.43). The magnitude of familial influences (i.e., both genetic and shared environmental influences) was lower in parent-offspring adoption studies than in both twin studies and sibling adoption studies. Operationalization, assessment method, zygosity determination method, and age were significant moderators of the magnitude of genetic and environmental influences on antisocial behavior, but there were no significant differences in the magnitude of genetic and environmental influences for males and females.     

A century of research on masculinity and femininity: a critical review

The psychological study of masculinity (M) and femininity (F) throughout the twentieth century shows two very different approaches. In the first half of last century, authors try to test the bipolar continuum hypothesis, whereas during the second half, the hypothesis of two orthogonal dimensions predominates. Empirical studies carried out in various countries with the classic M and F scales show that the data do not support: a) the bipolar continuum hypothesis; b) the close relationship between masculinity/men and femininity/women as the single pattern of functional development; and c) the convergence validity of the different assessment instruments. In turn, the empirical results obtained with the new M and F scales show: a) the multidimensionality instead of bi-dimensionality of the different scales; b) that the different M and F scales are not equivalent; and c) that there is no theory capable of guiding the development of new scales to assess these constructs. At the beginning of the 21st century, after the critical evaluation of the studies carried out during about 100 years, we face a critical question: is it worthwhile to continue talking about M and F within the field of science and, more specifically, within the field of psychology?     

Genetic and environmental influences on sexual orientation and its correlates in an Australian twin sample

We recruited twins systematically from the Australian Twin Registry and assessed their sexual orientation and 2 related traits: childhood gender nonconformity and continuous gender identity. Men and women differed in their distributions of sexual orientation, with women more likely to have slight-to-moderate degrees of homosexual attraction, and men more likely to have high degrees of homosexual attraction. Twin concordances for nonheterosexual orientation were lower than in prior studies. Univariate analyses showed that familial factors were important for all traits, but were less successful in distinguishing genetic from shared environmental influences. Only childhood gender nonconformity was significantly heritable for both men and women. Multivariate analyses suggested that the causal architecture differed between men and women, and, for women, provided significant evidence for the importance of genetic factors to the traits' covariation.     

Genetic and environmental bases of childhood antisocial behavior: a multi-informant twin study

Genetic and environmental influences on childhood antisocial and aggressive behavior (ASB) during childhood were examined in 9- to 10-year-old twins, using a multi-informant approach. The sample (605 families of twins or triplets) was socioeconomically and ethnically diverse, representative of the culturally diverse urban population in Southern California. Measures of ASB included symptom counts for conduct disorder, ratings of aggression, delinquency, and psychopathic traits obtained through child self-reports, teacher, and caregiver ratings. Multivariate analysis revealed a common ASB factor across informants that was strongly heritable (heritability was .96), highlighting the importance of a broad, general measure obtained from multiple sources as a plausible construct for future investigations of specific genetic mechanisms in ASB. The best fitting multivariate model required informant-specific genetic, environmental, and rater effects for variation in observed ASB measures. The results suggest that parents, children, and teachers have only a partly "shared view" and that the additional factors that influence the "rater-specific" view of the child's antisocial behavior vary for different informants. This is the first study to demonstrate strong heritable effects on ASB in ethnically and economically diverse samples.     

Multidimensional self-concepts,masculinity, and femininity as a function of women's involvement in athletics

Measures of multidimensional self-concepts, masculinity (M), and femininity (F) were completed by high-school women athletes and nonathletes, and by young-adult women athletes and nonathletes. Women athletes in both age groups had substantially higher scores in M and in self-concept of physical ability, but did not differ substantially from nonathletes in F and in other areas of self-concept. Women athletes in both groups also judged their self-concept of physical ability to be more important to them than did nonathletes, but the two groups did not differ in the perceived importance of other areas of self-concept. These findings support the androgyny contention that MF should not be considered a bipolar construct and suggest that women can be more M without being less F. The specificity of the relation between athletic involvement and the multiple dimensions of self-concept also provide further support for the construct validity of the self-concept dimensions.The authors would like to acknowledge Lindsay McCaughan for his assistance in the design of the study, the staff and students at Pymble Ladies College, and the group of female powerlifters.     

Age, gender, and individual differences in memory failure appraisal

Young adults (22 men and 24 women) and older adults (24 men and 24 women) rated 12 gender-neutral vignettes describing short-term, long-term, and very-long-term memory failures. Vignette target persons were young (21-32) or older (65-75) men or women. Subjects of both age and gender groups used a double standard: Failures of older targets of both genders were rated as signifying greater mental difficulty than failures of young targets; failures of young targets were attributed to lack of effort and attention. Young subjects judged very-long-term failures more harshly than did older subjects. Subjects' objective memory performance, self-rated memory failure frequency, memory failure discomfort, and depression made little difference in their target person ratings.     

Genetic and environmental influences on pubertal development: longitudinal data from Finnish twins at ages 11 and 14

To study sources of individual differences in pubertal development, the authors fit a sex-limitation common factor model to data reported, at ages 11 and 14 years, by 1,891 twin pairs on items that comprise the Pubertal Development Scale (PDS; A. C. Petersen, L. Crockett, M. Richards, & A. Boxer, 1988). The model divides variation into a general pubertal factor and item-specific variation and, in addition, decomposes it into constituent sources. In both boys and girls, genetic influences made the largest contribution to variance common to PDS items. Genetic and nonshared environmental factors accounted for variation specific to PDS items in boys, whereas for girls, common environmental influences were added for growth spurt and menarcheal status. For both common and item-specific variation, genetic effects were partially sex specific. Subsidiary analyses found accelerated maturation in both boys and girls who at age 14 were reared in father-absent homes.     

Motivational influences on cognitive control: Behavior,brain activation,and individual differences

What changes in brain activity are associated with changes in motivational state? The present study addressed this question by having participants perform a cognitive task (AX variant of the Continuous Performance Test; AX-CPT) under three different blocked motivational conditions (reward-incentive, penalty-incentive, and baseline). Behavioral data showed that the incentive conditions modulated task performance, potentially by altering participants’ cognitive control strategy. Neuroimaging data indicated that the reward condition was associated with a sustained increase in a primarily right-lateralized network that included parietal and prefrontal cortex. Additionally, individual differences were observed, such that activation in both reward-related brain regions and frontopolar cortex was linked to the degree of motivation-induced performance enhancement and to motivation-related personality variables. These results suggest that changes in motivational state may modulate performance through sustained activity in cognitive control regions and that the effect of incentives may be affected by the personalities of the participants.     

Visualizing individual differences in Web navigation: STRATDYN, a tool for analyzing navigation patterns

Navigational behavior on the Web can be analyzed with different methods. Log file data are an important source of behavioral traces of navigation. In this paper, we first discuss existing approaches to the classification and visualization of movement sequences that are important for understanding Web navigation. We then present STRATDYN, a tool that provides meaningful quantitative and qualitative measures from server-generatedlog files, as well as easy-to-follow visualizations of navigational paths of individual users. We demonstrate the usefulness of this new approach by reporting the results of two studies (with 44 students in education and vocational training), which show that navigational effectiveness is positively related to the ability to concentrate and selectivelyfocus attention, as measuredby the D2 Test of Attention and the FWIT, a German version of the Stroop test. Finally, we discuss implications for further research in this area and for the continuing development of the approach presented.     

Remembering talk: individual and gender differences in reported speech

This study examined individual and group differences in the nature and frequency of reports of past speech in the autobiographical memories of young adults. A sample of 108 participants (60 females, 48 males) responded in writing to six memory prompts. They also completed the Five Factor Inventory (Costa & McCrae, 1992) and the Personal Attributes Questionnaire (Spence & Helmreich, 1978). The frequency with which participants used reported speech was correlated with agreeableness, openness, and expressivity; however, regression analyses indicated that narrators' gender alone was the best predictor. Females used more reported speech than did males. The findings suggest that recollections of past speech are an under-appreciated yet important component of autobiographical memory.     

Genetic and environmental covariance structures among WISC-R subtests: A twin study

Genetic and environmental correlations among 11 Wechsler Intelligence Scale for Children-Revised (WISC-R) subtests were estimated from a sample of 143 twin pairs using the methodology of multivariate behavioral genetics. The genetic correlations among subtests varied in magnitude and exhibited a pattern similar to corresponding phenotypic correlations. Correlations due to within-pair environmental influences were generally small, whereas those due to shared environmental influences tended to be intermediate. Several hypotheses regarding the structures of the additive-genetic, common environmental, and within-pair environmental covariance matrices were tested and evidence for differential factor structures was obtained. A model hypothesizing a three-factor structure for the genetic covariance matrix, a single factor for the common environmental matrix, and a single factor plus specifics for the within-pair environmental matrix fit the data well. Thus, the three-factor phenotypic structure typically observed in Wechsler Intelligence Scale for Children (WISC) data may be due largely to genetic influences.     

Developmental and individual differences in preschoolers' recognition memories: The influences of gender schematization and verbal labeling of information

Eighty-three 37-92-month-old children's gender schematization and recognition memories for gender-typed content were assessed. Verbal labeling of stimuli and age were positively associated with children's memories. Highly gender schematic children displayed better memories for gender-role consistent information and committed more gender transformation errors than less gender schematic children. Interactions between children's gender schematization, age, and labeling condition were observed. Labeling of stimuli facilitated less schematic children's memories for gender-role consistent information. Gender schematization was positively associated with younger children's memories, suggesting younger children's memories are more strongly mediated by gender schematization than older children's. Results support the position that studies of gender schema development require an integrated approach recognizing individual and developmental differences in gender schematic processing.Completion of this project was facilitated by funds received while the author was a National Institute of Mental Health Postdoctoral Fellow at the University of Denver: Grant 5T32 MH 15780-09. This support is gratefully acknowledged. An earlier version of this paper was presented at the Conference on Human Development, Charleston, South Carolina, 1988. The author would like to thank the faculty and staff of the Tiny Tot, Jack & Jill, Little Learners II, Plymouth and Upstate preschools for their assistance and cooperation. The author wishes to recognize James Aber, Rosanne David, Melisa Shack, and Susan Zigelbaum for their exceptional service in conducting the project; and would also like to thank Joan Barth, D. Bruce Carter, Gail S. Goodman, Carol L. Martin, William J. Meyer, Kathy Park, Ralph J. Roberts, Jaipaul L. Roopnarine, Margaret L. Signorella, and the anonymous reviewers for their comments and suggestions on earlier drafts of this article.     

Genetic and environmental influences on the relationships between family connectedness, school connectedness, and adolescent depressed mood: sex differences.

This study investigated (a) genetic and environmental contributions to the relationship between family and school environment and depressed mood and (b) potential sex differences in genetic and environmental contributions to both variation in and covariation between family connectedness, school connectedness, and adolescent depressed mood. Data are from 2,302 adolescent sibling pairs (mean age = 16 years) who were part of the National Longitudinal Study of Adolescent Health. Although genetic factors appeared to be important overall, model-fitting analyses revealed that the best-fitting model was a model that allowed for different parameters for male and female adolescents. Genetic contributions to variation in all 3 variables were greater among female adolescents than male adolescents, especially for depressed mood. Genetic factors also contributed to the correlations between family and school environment and adolescent depressed mood, although, again, these factors were stronger for female than for male adolescents.     

Gender-related traits in gay men, lesbian women, and heterosexual men and women: the virtual identify of homosexual-heterosexual diagnosticity and gender diagnosticity

Three studies investigated the relationship between gender-related traits and sexual orientation. Study 1 showed that gay men and lesbians in an unselected sample of 721 college students differed from same-sex heterosexuals most strongly on gender diagnosticity (GD) measures, which assess male- versus female-typicality of interests (effect sizes of 2.70 for men and .96 for women) and least strongly on measures of instrumentality (I) and expressiveness (E). In Study 2, GD measures showed large differences between 95 gay and 136 heterosexual men (effect sizes of 1.61 and 1.83) and between 46 lesbian and 225 heterosexual women (effect sizes of .98 and 1.28), whereas I and E showed much smaller differences. In Study 3, GD showed large differences between 90 gay and 81 heterosexual men (effect sizes of 1.76 and 1.97) and between 82 lesbians and 108 heterosexual women (effect sizes 1.67 and 1.70). whereas I and E showed much smaller differences. Using data from Studies 2 and 3, "gay-heterosexual diagnosticity" measures were computed for men and "lesbian-heterosexual diagnosticity" measures for women, based on occupational and hobby preferences. These measures correlated very strongly with GD measures.     

An individual differences analysis of ability and strategy influences: age-related differences in associative learning

The relationships among abilities, strategies, and performance on an associative learning task were investigated for young (aged 17 to 34) and older adults (aged 60 to 82). Participants received extensive practice on a noun-pair task in which they could use a visual-scanning strategy or a memory-retrieval strategy. Older adults were more likely to use the scanning strategy. Age differences were reduced when comparisons were made only for participants using a retrieval strategy. Associative memory was predictive of learning on the task, and semantic memory access speed was predictive of practiced performance. Practiced performance on a memory-search task that also required associative learning was predictive of practiced noun-pair performance. Models of ability-performance relationships for skill acquisition are discussed.