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The Adolescent Brain Cognitive Development (ABCD) Study®is a 10-year longitudinal study of children recruited at ages 9 and 10. A battery of neuroimaging tasks are administered biennially to track neurodevelopment and identify individual differences in brain function. This study reports activation patterns from functional MRI (fMRI) tasks completed at baseline, which were designed to measure cognitive impulse control with a stop signal task (SST; N= 5,547), reward anticipation and receipt with a monetary incentive delay (MID) task (N= 6,657) and working memory and emotion reactivity with an emotional N-back (EN-back) task (N= 6,009). Further, we report the spatial reproducibility of activation patterns by assessing between-group vertex/voxelwise correlations of blood oxygen level-dependent (BOLD) activation. Analyses reveal robust brain activations that are consistent with the published literature, vary across fMRI tasks/contrasts and slightly correlate with individual behavioral performance on the tasks. These results establish the preadolescent brain function baseline, guide interpretation of cross-sectional analyses and will enable the investigation of longitudinal changes during adolescent development.

The detailed results of a triple test cross using wild rats crossed to partially inbred sublines of the Roman High and Low Avoidance selection strains clearly indicated considerable amounts of additive genetic variation in the wild population for avoidance performance while there is a general absence of nonadditive variation, with the exception of some dominance variation together with duplicate type epistasis. Where present, directional dominance for this phenotype is toward high performance only for later trials, and the effects of any epistasis reinforce this trend. The overall conformity of these results to the predictions from previous laboratory rat studies suggests no reason to reject the representativeness assumption necessary for arguments from genetic architecture in laboratory populations to adaptive significance in contemporary wild populations.

Data from a diallel cross of six lines composing a replicated selection study for open-field behavior in mice are reanalyzed to investigate the generality of the findings. The results support the hypothesis that only additive variation would be found for open-field behavior if additional selection lines were derived from the same foundation population.

Rats from five strains were tested for the ability precognitively to avoid three levels of shock. There were clear effects of shock and strain on the number of observed Random Behaviour Trials, with the Roman High Avoidance strain being the only one to maintain high levels of Random Behavior Trials at high levels of shock. However, there was no evidence for any psi ability in this experiment and this null result was not affected by either the strain of rat tested or the level of shock delivered. There was no interaction among these factors.

We review the conditions under which cross-sectional family data (e.g., data on twin pairs or adoptees and their adoptive and biological relatives) are informative about direction of causation. When two correlated traits have rather different modes of inheritance (e.g., family resemblance is determined largely by family background for one trait and by genetic factors for the other trait), cross-sectional family data will allow tests of strong unidirectional causal hypotheses (A and B are correlated “because of the causal influence of A on B” versus “because of the causal influence of B on A”) and, under some conditions, also of the hypothesis of reciprocal causation. Possible sources of errors of inference are considered. Power analyses are reported which suggest that multiple indicator variables will be needed to ensure adequate power of rejecting false models in the presence of realistic levels of measurement error. These methods may prove useful in cases where conventional methods to establish causality, by intervention, by prospective study, or by measurement of instrumental variables, are infeasible economically, ethically or practically.

A common procedure for assessing children's behavior is to obtain parental ratings of the child. Since the ratings obtained are a function of both parent and child, disentangling the child's phenotype from that of the rater becomes an important methodological problem. For the analysis of genetic and environmental contributions to children's behavior, solutions to this are available when multiple raters, e.g., two parents, rate multiple children, e.g., twins. This paper describes and illustrates simple LISREL models for the analysis of parental ratings of children's behavior. We show how the assumption that mothers and fathers are rating the same behavior in children can be contrasted with the weaker alternative that parents are rating correlated behaviors. Given the stronger assumption, which appears adequate for ratings of children's internalizing behavior problems, the contribution of rater bias and unreliability may be separated from the shared and nonshared environmental components of variation in a behavior genetic analysis.

Young male twins in The Netherlands and England completed the Jenkins Activity Survey (Dutch and English versions, respectively), a measure of Type A behavior. Separate model fitting analysis revealed a similar pattern of variance estimates and associated goodness of fit across the two countries. The data were then analyzed concurrently, with a scalar parameter included to account for differences in variance due to the disparity of the measurement scales. A model including additive genetic and individual environmental effects gave a good explanation to the data. The heritability estimate was 0.28. Models of social interaction and dominance explained the data even better, the former being preferred. The twins' parents were included in the analysis to examine population variation for Type A behavior intergenerationally. There was evidence for individual environmental experiences having a greater influence on Type A behavior in the older generation.

Four inbred strains of mice, DBA/2J, C57BL/10J, BALB/cJ, and SJL/J, were mated in a diallel cross. The cerebella of the F1 generation were examined for the presence (Type I) or absence (Type II) of an intraculminate fissure between vermian lobule IV and vermian lobule V (the ventral and dorsal lobules of the culmen). One strain (DBA/2J) consistently expressed the Type I pattern. Another strain (SJL/J) expressed predominantly the Type II pattern. The other two strains (C57BL/10J and BALB/cJ) and many of the hybrids exhibited variability in their expression of the foliation patterns. The results were analyzed using biometrical genetic procedures and showed significant additive and dominance genetic effects and a maternal effect. Correlations of these cerebellar anatomical variants with the development of behavior are discussed.

The relationship between reproductive success (number of biological children) and personality was explored in 1101 postmenopausal females from the Australian twin registry. The quadratic response surface relating fitness to extraversion (E) and neuroticism (N) showed a saddle point at intermediate levels of E and N. Selection was shown to be stabilizing, i.e.,having an intermediate optimum, along the axis low E, low N-high E, high N and more mildly disruptive, having greater fitness in the extremes, along the axis low N, high E-high N, low E. Neither dimension of personality considered by itself showed a significant linear or quadratic relationship to reproductive success. Sections through the fitness surface, however, show selection tends to favor high neuroticism levels in introverts and low neuroticism levels in extroverts.

Martin and Wilson (1982) describe two forms of sampling bias in twin studies. One is “hard selection,” where individuals above a threshold participate, and those below do not. The second is “soft selection,” where the probability of including a pair of relatives varies over the range of the character. We present an alternative model of soft selection which has strikingly different consequences for the resemblance between relatives. In general, the softer the threshold, the more the correlation resembles that in the underlying population. Results are presented where the probability of selection equals the cumulative distribution function of a normal distribution with 10% of the variance of the selected variable. In these circumstances, soft selection usually leads to less severely attenuated correlations than truncate selection.

A brief introduction to the mathematical theory involved in model fitting is provided. The properties of maximum-likelihood estimates are described, and their advantages in fitting structural models are given. Identification of models is considered. Standard errors of parameter estimates are compared with the use of likelihood-ratio (L-R) statistics. For structural modeling, L-R tests are invariant to parameter transformation and give robust tests of significance. Some guidelines for fitting models to data collected from twins are given, with discussion of the relative merits of parsimony and data description.

Simple genetic models can be fitted to twin data using software packages such as LISREL (Jöreskog and Sörbom, 1986a). After discussion of data preparation and routine checks on possible violation of assumptions of the twin method, we illustrate univariate, bivariate, and multivariate genetic models which can be tested in cross-sectional twin data using LISREL. These include models for cohort or cohabitation effects, genotype x sex interaction, and certain types of genotype x environment interaction and genotype-environment correlation.

Power calculations for a variety of research designs used in behavior genetics require the determination of a chi-square noncentrality parameter. For many purposes published tables are adequate, but for cases where they are not we provide a graph for approximating the required parameters for up to 300 degrees of freedom and illustrate a straightforward procedure for accurate determination using a widely available SAS function.

Rats of 18 genotypes derived from the Roman selected strains were tested for inhibition of feeding due to novelty (hyponeophagia) in the absence or presence of 1 mg/kg diazepam. The resulting data from three behavioral indices were subjected to the Hayman [(1954). Biometrics10:235–244], variance/covariance, Mendelian cross, and single-test cross analyses. Additive genetic variation, directional dominance for high neophobia, and some nonallelic interaction were detected. The genetic architecture of the separate behavioral indices, and its modification in the drugged subjects, was discussed in relation to evolutionary adaptation and the anxiolytic and appetite-enhancing actions of the drug.

A wild x laboratory rat triple test-cross study of open-field defecation, open-field ambulation, and a measure of rearing-up activity in a non-stressful environment revealed three different patterns of results. For open-field defecation, where the tester lines were expected to be inadequate to detect nonadditive variation, only putative additive effects were detected and a minimum broad heritability of 20% in the wild population was revealed. For open-field ambulation an architecture including ambidirectional dominance was in line with laboratory rat studies, while for rearing behavior epistatic effects were indicated. The implications of these results for domestication and for past and future evolution are discussed.

Data were obtained from a retrospective review of the records of 125 women who had undergone full urodynamic studies for a variety of clinical indications, to determine whether urethral instrumentation has an adverse effect on the parameters of urine flow in women. All patients had an initial urine flow study with a spontaneous void of at least 100 ml, after which they were catheterized to measure the postvoid residual urine. All patients then underwent urethral pressure studies, complex filling cystometry, pressure-flow voiding studies and urethrocystoscopy, after which they underwent another spontaneous non-instrumented urine flow study. Peak and mean flow rates were analysed statistically by blocked analysis of variance. The data were corrected for the effects of the volume voided by converting the flow rates into a nomogram percentile ranking using a computer program.

Scores from 1492 adult subjects on the Public Opinion Inventory were subjected to principal components and factor analyses. The adequacy of a two-factor hypothesis and the factors' correspondence to the dimensions of Radicalism and Toughmindedness previously defined were confirmed.

Biometrical genetic analysis of the elements of the male courtship sequence in D. melanogaster using diallel and Cavalli cross-breeding designs, revealed that the genetic architecture of the overall level of courtship was characterised by low additivity, sex-linkage and directional dominance for higher levels of courtship. Similar genetic architectures were found for the latter elements of the courtship sequence, with directional dominance for increased amounts of wing vibration, licking, attempted copulation and copulation itself. There was no evidence of sex-linkage for these characters but there was also evidence of some i-type epistatic variation for the wing vibration component of the courtship sequence. The first element of the courtship sequence, orientation, showed a different pattern of inheritance, with again low additive genetic variation but directional dominance for low levels of orientation. These fitness type genetic architectures suggest that the individual elements of the courtship sequence have had a recent history of directional selection favouring a shorter phase of orientation and higher expression of the other courtship elements. This may imply that, though orientation will occur in the initial stages of the courtship process, selection favours males that proceed to the later, more important elements of the courtship sequence fastest.Heredity (1984) 53, 321–337; doi:10.1038/hdy.1984.91

SummaryIn a triple test cross F2males are backcrossed to females from both the parental inbred lines and from an F1cross between them. A previously suggested test for the direction of dominance uses the covariance over sires of the sums and differences of the mean scores of the backcrosses to the inbred lines. This test is biased in the presence of some types of genotype × environment interaction while an alternative test using the covariance over sires of the means of the backcrosses to the F1with differences between the backcrosses to the inbred lines is not. A comparison of the two covariances could provide a scaling test for this breeding design.Heredity (1980) 45, 293–295; doi:10.1038/hdy.1980.69