Understanding the Covariation Among Childhood Externalizing Symptoms: Genetic and Environmental Influences on Conduct Disorder,Attention Deficit Hyperactivity Disorder,and Oppositional Defiant Disorder Symptoms

Conduct disorder (CD), attention deficit hyperactivity disorder (ADHD), and oppositional defiant disorder (ODD) are common childhood externalizing disorders that frequently co-occur. However, the causes of their comorbidity are not well understood. To address that question, we analyzed data from > 600 Finnish twin pairs, who completed standardized interviews at age 14. Behavior genetic methods were used to examine how genetic/environmental factors contribute to each disorders symptoms and to their covariation. We found significant genetic effects on each disorder with only modest evidence of shared environmental influences. Our data suggest the comorbidity among CD, ADHD, and ODD is primarily explained by shared genetic influences; however, each disorder was also under unique genetic influence, supporting the distinction of each disorder.     

Influence of Sexually Degrading Music on Men's Perceptions of Women's Dating‐Relevant Cues

This study examined the influence of manipulated and naturalistic exposure to sexually degrading music on young men's perceptions of women's dating‐relevant affective cues. Three hundred ninety‐seven undergraduate heterosexual men completed an affect‐identification task in which they judged whether women communicated sexual interest, friendliness, sadness, or rejection. Either sexually degrading popular music, non‐sexually degrading popular music, or no music played on headphones. Participants completed questionnaires assessing music‐listening habits and rape‐supportive attitudes. Manipulated exposure to degrading music did not affect men's sensitivities to or biases for women's cues. In contrast, men who reported greater naturalistic exposure to rap and hip‐hop music and who endorsed more rape‐supportive attitudes were more likely to perceive women's positive affect as sexual interest, if the women were provocatively dressed. On balance, these findings are largely inconsistent with theoretical expectations regarding the deleterious effects of sexually degrading music on attitudes and concurrent social perception. Copyright © 2014 John Wiley & Sons, Ltd.     

Sex differences in genetic and environmental effects on aggression

The aim of the present study was to investigate the genetic and environmental factors influencing teacher and parental rated aggression in boys and girls, asking whether the magnitude of these effects is similar across rater and sex. The study is part of an ongoing nationwide twin‐family study of behavioral development and health habits carried out in Finland. The sample consisted of 1651 twin pairs (264 monozygotic male, 300 monozygotic female, 292 dizygotic male, 278 dizygotic female, and 517 dizygotic opposite‐sex twin pairs), representing subsets of five 11‐ to 12‐year‐old twin cohorts (b. 1983–1987). The data were collected using the teacher and parental rating forms of the Multidimensional Peer Nomination Inventory. Structural equation models of sex‐limitation assessed sex differences in genetic and environmental influences on aggression. The results suggested significant genetic, common environmental, and specific environmental effects on aggression in both boys and girls, but the best fitting model differed depending on the informant. For both ratings, boys showed lower levels of heritability and higher levels of common environment than girls. In addition, the teacher rating data also suggested the presence of either sex‐specific common environmental effects or sex‐specific genetic effects. Support is provided also for sibling contrast effects, either at the behavioral level or as a rater bias. Aggr. Behav. 29:55–68, 2003. © 2003 Wiley‐Liss, Inc.     

Assessing clinically relevant perceptual organization with multidimensional scaling techniques

Multidimensional scaling (MDS) techniques provide a promising measurement strategy for characterizing individual differences in cognitive processing, which many clinical theories associate with the development, maintenance, and treatment of psychopathology. The authors describe the use of deterministic and probabilistic MDS techniques for investigating numerous aspects of perceptual organization, such as dimensional attention, perceptual correlation, within-attribute organization, and perceptual variability. Additionally, they discuss how formal quantitative models can be used, in conjunction with MDS-derived representations of individual differences in perceptual organization, to test theories about the role of cognitive processing in clinically relevant phenomena. They include applied examples from their work in the areas of eating disorders and sexual coercion.     

Pubertal timing and substance use: associations between and within families across late adolescence

In the present study, between-family analyses of data from adolescent twin girls offer new evidence that early menarche is associated with earlier initiation and greater frequency of smoking and drinking. The role of personality factors and peer relationships in that association was investigated, and little support was found for their involvement. Novel within-family analyses replicating associations of substance use with pubertal timing in contrasts of twin sisters selected for extreme discordance for age at menarche are reported. Within-family replications demonstrated that the association of pubertal timing with substance use cannot be explained solely by between-family confounds. Within-family analyses demonstrated contextual modulation of the influence of pubertal timing: Its impact on drinking frequency is apparent only among girls in urban settings. Sibling comparisons illustrate a promising analytic tool for studying diverse developmental outcomes.     

Sexual behavior in young adulthood: a population-based twin study.

OBJECTIVE: With behavior genetic analyses of data from young adult twins, we evaluated theoretical perspectives that differentially emphasize biological dispositions, social/cultural factors, or universal pathways to explain individual differences in sexual behaviors. DESIGN: We fit biometric sex limitation models to three aspects of sexual behavior reported by 4,925 Finnish twins ages 23-27. MAIN OUTCOME MEASURE: From a postal questionnaire, we obtained self-report information on initiation/abstinence of sexual intercourse, onset age, and number of sexual partners. RESULTS: Genetic and non-shared environmental influences were significant for all three measures. There were trends for common environmental influences on initiation and, in females, age at first intercourse. Some differential effects in males and females were found. Results comparing onset age and number of partners among experienced twins from pairs concordant and discordant for initiation found genetic and environmental influences on initiation/abstinence overlapped those found for the other aspects of sexual behavior. CONCLUSIONS: These results document genetic variation in individual differences in sexual behavior of young adults. Incorporating genetic dispositions into integrated models of sexual behavior will facilitate more effective health promotion and risk taking intervention.     

Genetic variation and covariation in the original and restructured clinical scales of the MMPI

The authors investigated genetic variation and covariation among the original Minnesota Multiphasic Personality Inventory clinical and validity scales and the restructured clinical scales. Variation in most of these scales was best explained by a combination of moderate genetic influences and environmental influences not shared by cotwins. Genetic correlations among the standard clinical scales were generally substantial and positive (M = .48), whereas genetic correlations between the clinical scales and the K scale were strong and negative. The restructured clinical scales were strongly correlated with the general Demoralization scale (M = .55), with lower genetic correlations among the remaining scales (M = .39).     

Relationship between shock-induced aggression and other laboratory tests of agonistic behavior in rats

The utility of the shock-induced aggression paradigm has been questioned in recent years. Studies were reviewed that demonstrated similar effects of independent variables on shock-induced, resident-intruder, and home-cage aggressive behavior. Correlations between naturally occurring aggression and shock-induced aggression, studies showing the influence of naturally occurring agonistic experience on shock-induced aggression, and the effects of shock-induced aggressive experience on resident-intruder behavior were also reviewed. It was argued that continued research into shock-induced aggression and its relationship to other laboratory paradigms would be useful, and that abandonment of the paradigm at this time would be premature.