Determinants of sexual and dating behaviors among adolescents

The study of adolescent sexual development has typically focused on the incidence and age of onset of particular behaviors. Recent developments in the analysis of covariance structures permit more powerful simultaneous tests of the determinants of adolescent sexual behavior. These new methods allow the assessment and evaluation of the interrelatedness between unobserved, latent constructs. Data were obtained from 183 males and 193 females ranging in age from 12 to 18 years old, selected from three birth cohorts using a stratified random sample. Eight latent constructs--Sexual and Dating Involvement, Self-Acceptance, Feminist Sex Role Attitudes, Deviant Social Network, Importance of Dating, Lack of Heterosexual Competence, Sexually Active Social Network, and Stressful Change Events--were hypothesized to explain the variance in 26 observed variables. Several causal models were tested that specified structural relationships among the latent constructs. A theoretically meaningful model was arrived at that linked the eight, error-free factors.     

Attenuation of Hippocampal 11beta-Hydroxysteroid Dehydrogenase Type 1 by Chronic Psychosocial Stress in the Tree Shrew

11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD-1) catalyses the interconversion of active cortisol and corticosterone with inert cortisone and 11-dehydrocorticosterone, thus regulating glucocorticoid access to intracellular receptors. In rats, chronic glucocorticoid excess or stress increases 11beta-HSD-1 in the hippocampus, producing suggestions that it may attenuate the deleterious effects of chronic glucocorticoid excess. However, 11beta-HSD-1 predominantly catalyses 11beta-reduction in the intact liver and hippocampal cells, thus regenerating active glucocorticoids from inert substrate. We studied 11beta-HSD activity in the tissues of male tree shrews following 28 days of sustained psychosocial stress or exogenous administration of cortisol. In the hippocampus, chronic psychosocial stress attenuated 11-HSD-1 activity (69 +/- 9% of control), whereas cortisol alone had no effect. In the liver, both chronic stress and cortisol administration decreased 11beta-HSD-1 activity (47 +/- 11% and 49 +/- 4% fall, resp.). Attenuation of 11beta-HSD-1 within tissues may reflect a homeostatic mechanism designed to minimise the adverse effects of prolonged stress and/or glucocorticoid excess.     

Matrix derivatives with chain rule and rules for simple,Hadamard, and Kronecker products

The differential calculus for scalars is used to develop theorems for a calculus of functions of matrices. No appeal to scalar notation is necessary in the resulting calculus, so that the given chain and matrix product rules have wide applicability to matrix theory and models. The chain and product rules of scalar calculus become a special case of the matrix rules. The methods are illustrated by application to a generalized stochastic process model potentially relevant to long- and short-term memory.     

A longitudinal analysis of personality structure and adolescent substance use

Within the context of a prospective longitudinal research design, the structure of personality and initial levels of drug use were used to predict, multivariately, later drug use among male and female adolescents. The findings indicated that personality and belief measures of nonconventionality provide a significant increment in the prediction of later drug use beyond a level achieved by knowing initial usage rates. In addition, other personality and belief measures yield further increments in the prediction of subsequent drug use. Developmentally, the results revealed a differentiation of drug use patterns across the year's time, with one pattern primarily reflecting alcohol use, and a second pattern primarily reflecting use of marijuana and ‘hard’ drugs. While both patterns were related to measures of nonconventionality, certain personality features distinguished between them. Emergent use of marijuana and ‘hard’ drugs was related to depression, mistrust and attractiveness, while emergent alcohol use was related to generosity, ambition, agility and cheerfulness. These results were cross-validated in two samples of subjects. Implications of the findings for adolescent psychosocial development are discussed.     

Assessment of personality and demographic aspects of cohabitation and marital success

The outcomes of 68 marriages of four-year duration were compared on the basis of whether the partners had or had not cohabited premaritally. Background characteristics and personality data were assessed on those couples when there were newly married, and they were followed-up four years later to determine their current marital status, level of satisfaction, difficulty with various problem areas and the number of children born to them. No reliable differences on marital satisfaction or divorce rates between premarital cohabitors and noncohabitors were found. Cohabitors who divorced did so while reporting less marital distress than noncohabitors who divorced. Premarital cohabitors had significantly fewer children than noncohabitors. Degree of difficulty experienced on various problem areas differed between the groups. Certain personality and background variables predicted marital success differently for the two groups. Using the same selected set of six predictor variables, multiple regression equations were generated for cohabitors and noncohabitors. The cohabitors equation (R2 = .56) predicted marital success significantly more effectively than the noncohabitors equation (R2 = .28), When comparing the tri-weight vectors for these two equations, none of the predictor variables had the same influence in both groups. Theoretical implications of the findings were discussed.     

Tests for stability in linear structural equation systems

Interpretations regarding the effects of exogenous and endogenous variables on endogenous variables in linear structural equation systems depend upon the convergence of a matrix power series. Convergence depends upon the eigenvalues of the structural coefficient matrix. The test for convergence developed by Jöreskog and Sörbom is shown to be only sufficient, not necessary and sufficient.     

Cognitive motivation and drug use: a 9-year longitudinal study.

The predictive precedence of expectancy constructs, operationally defined as cognitive motivations, and drug use was investigated over a 9-year period from adolescence to adulthood. Alternative predictions from three different classes of theories of expectancy-behavior relations, including expectancy theory, a Skinnerian approach, and a reciprocal determinism perspective, were evaluated. The results are most consistent with the notion based in expectancy theory that cognitive motivations are nonspurious and possibly functionally autonomous influences on the use and abuse of drugs. More limited support is found for the view that drug use leads to cognitive motivations, as postulated in other theoretical perspectives. Other findings reveal the presence of expectancy generalization processes consistent with Rotter's (1954) expectancy theory, as well as the unique status of cognitive motivations for alcohol as an independent predictor of problem drug use.     

Restricted multidimensional scaling models for asymmetric proximities

Restricted multidimensional scaling models [Bentler & Weeks, 1978] allowing constraints on parameters, are extended to the case of asymmetric data. Separate functions are used to model the symmetric and antisymmetric parts of the data. The approach is also extended to the case in which data are presumed to be linearly related to squared distances. Examples of several models are provided, using journal citation data. Possible extensions of the models are considered. This research was supported in part by USPHS Grant 0A01070, P. M. Bentler, principal investigator, and NIMH Grant MH-24819, E. J. Anthony and J. Worland, principal investigators. The authors wish to thank E. W. Holman and several anonymous reviewers for their valuable suggestions concerning this research.