Simulated data, validity reports and a firefighter predictive validation study are used to examine validity bias created by three common selection problems-range restriction, applicant and incumbent ...attrition, and nonlinearity created by compression of high selection test scores. Top 20% selection samples drawn from an applicant pool with known validity coefficients demonstrate that the sample validity estimates of the three predictors are differentially biased in both magnitude and direction, depending on the selection strategy used. Concurrent validity designs generally favor novel predictors. Corrections for direct range restriction across situations were mostly ineffectual. With proper scaling, corrections for indirect range restriction are accurate, but cross-variable biasing effects can occur when score distributions of the individual predictors differ. Many of the biases found in the simulation results are demonstrated in a firefighter predictive validation study where variations of Pearson-Thorndike range corrected validities and a full information maximum likelihood (FIML), approaches are all compared as validity assessments. With normalized predictors, both Pearson and FIML methods show that a test of general mental ability and physically demanding job tasks predicted firefighter performance throughout the 30-year study, with no evidence of interactions or a leveling of performance at high test scores.
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BFBNIB, DOBA, FSPLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Firefighters from 1 academy training class were observed for 23 years, beginning with their selection test consisting of a g‐saturated written exam (GCA) and firefighting simulations loaded on a ...strength/endurance (SE) factor. Operational validity coefficients for both GCA and SE were high for training success and remained consistently high for job performance ratings throughout the study. The operational validity for combined GCA and SE predictors was .86 for a composite job rating measure covering 21 years of service. A structural model produced similar results for more broadly defined GCA and SE latent variables. Both analyses suggested approximately equal weighting for GCA and SE for a fire service selection test. Results indicate considerable latitude in choosing cognitive and physical predictors for firefighter screening if the predictors are highly loaded on GCA and SE.
In a test battery consisting of an open-field arena, a light-dark box, a mirror-chamber box, an elevated plus maze, and an elevated square maze, 1,671 mice were tested, generating over 100 putative ...measures of anxiety in rodents. Quantitative trait loci (QTL) analysis was carried out on all measures, plus composite measures and phenotypic factor scores. Significant LOD scores were found for QTL on 17 chromosomes, with large and consistent QTL behavioral effects on chromosomes 1, 4, 7, 8, 14, 15, l8, and X. QTL on chromosomes 4 and 8 largely influence locomotor activity in both home cages and novel environments, whereas QTL on chromosomes 1, 15, and 18 influence anxiety-related behaviors. Five genetically separable, cross-test dimensions of anxiety could be identified: (i) the suppression of locomotor activity in low to moderately anxiogenic regions of the tests; (ii) a shift toward proportionally less time and activity spent in high-anxiogenic test areas; (iii) the suppression of rearing behavior; (iv) increased latency to enter novel areas; (v) increased autonomic responses, as assessed by defecation and urination. Patterns of QTL influence on cross-test composite scores were distinctive. For example, the QTL on chromosome 1 strongly influenced safe-area locomotor activity (LOD = 35) and autonomic responses (LOD = 16), whereas the QTL on chromosome 15 influenced the proportion of activity in high-anxiogenic areas (LOD = 16), latency to enter novel areas (LOD = 36) and rearing behavior (LOD = 57). Phenotypic factor analysis identified factors heavily loaded on single tests, rather than cross-test factors. The use of factor analysis or within-test principal components for data reduction before genetic analysis was less satisfactory than using genetic dissection methods on the original measures and logically derived composites.
The outer membrane β-barrel trans-membrane proteins in gram-negative bacteria are folded into the membrane with the aid of polypeptide transport-associated (POTRA) domains. These domains occur, and ...probably function, as a tandem array situated on the periplasmic side of the outer membrane. Two crystal structures and one NMR study have attempted to define the structure and articulation of the POTRA domains of the Escherichia coli, prototypic Omp85 protein BamA. We have used pulsed electron paramagnetic resonance (EPR) to determine the distance and distance distribution between (1-Oxyl-2,2,5,5-tetramethylpyrroline-3-methyl) methanethiosulfonate spin labels (MTSSL), placed across the domain interface of the first two POTRA domains of BamA. Our results show tightly defined interdomain distance distributions that indicate a well-defined domain orientation. Examination of the known structures revealed that none of them fitted the EPR data. A combination of EPR and NMR data was used to generate converged structures with defined domain-domain orientation.
Recruits from 9 consecutive fire academy classes were assessed on a battery of strength and endurance measures at Weeks 1, 7, and 14 of training. Regression analyses using Week 1 measures indicated ...that strength variables were the primary predictors of performance on physically demanding firefighting tasks assessed at the completion of training. Incremental validity was obtained with the addition of aerobic capacity, which produced more accurate performance distinctions among recruits with high strength levels. Results showed predictive validity and linearity throughout the upper range of strength and endurance levels, but evidence of an increased drop‐off in performance for recruits with strength levels below the male 25th percentile. Structural equation modeling, a more powerful and comprehensive approach to validation than traditional regression, provided strong support for the construct validity of general strength and endurance as predictors of firefighter performance on physically demanding fire suppression and rescue tasks.
Bidirectional selection in rodents has been used to derive animal models of human behavior. An important question is whether selection for behavior operates on a limited number of QTL or whether the ...number and individual contribution of QTL varies between selection experiments. To address this question, we mapped QTL in two large F2 intercrosses (N = 815 and 821) from the four lines derived from a replicated selection experiment for open-field activity, an animal model for susceptibility to anxiety. Our analyses indicate that selection operated on the same relatively small number of loci in both crosses. Haplotype information and the direction of effect of each QTL allele were used to confirm that the QTL mapped in the two crosses lie in the same chromosomal regions, although we were unable to determine whether QTL in the two crosses represent the same genes. We conclude that the genetic architecture of the selected strains is similar and relatively simple.
A method for partitioning environmental correlations into two distinct sources of covariation--lifetime rearing effects and idiosyncratic stimulus events occurring during testing ("noise")--is ...presented. The method, which is based on structural equation modeling of repeated tests, is demonstrated using correlations obtained from pairs of sessions in an Open Field Test and in a Light-Dark Test. Heritabilities of most behaviors are low, but genetic correlations between- and within-test sessions are high and thus substantively influence phenotypic correlations, including test-retest reliability. Testing "noise" is usually the primary source of environmental covariance among pairs of measures, although some instances of rearing environment being the sole source of E correlations were observed. Effects of Session 1 testing and/or the additional experience between S1 and S2 test sessions produce some significant differences between S1 and S2 within-session correlations, but these are usually not large. Although varying in size, the genetic, the rearing environment and the test environment correlations between a pair of variables were always consistent in sign. The analysis demonstrates the value of incorporating some of the contemporary research and analytic strategies used in the human individual differences field into animal studies.
Often a single pair of lines that has been selected for high and low expression of a trait is used as an animal model to study new biobehavioral characters thought to be associated with the selected ...trait. Because of genetic drift at many loci, comparisons of High and Low lines on the new character will frequently produce significant line differences even when there is no association between the selected trait and the new character being studied. In the absence of replicate lines to estimate the degree of genetic drift, effect size can be used to reduce the number of false-positive associations between the original selected trait and the new character. When the heritability of the new character exceeds .40 and the inbreeding coefficient within the selected lines is moderate, High- and Low-line means on the new character will frequently differ by at least one phenotypic SD, but not often differ by more than two SDs, in the absence of any relationship between the selected trait and the new character. If the selected lines are highly inbred, drift effects are greater, resulting in more false-positive associations. Situations posing special difficulty in the absence of replicate lines include the study of characters with low heritability relative to the selected trait and cases in which the lines do not differ greatly on the original selected trait. Studies using selected lines should always report inbreeding coefficients of the generations being studies, relative to the base population from which the lines were derived.
The number and mode of action of quantitative trait loci (QTL) that contribute to behavioral variation in rodents is still largely unknown. On theoretical grounds, multivariate techniques are ...expected to yield new insights into this problem, but there are only a few examples of its application in practice. Here we explore the power of multivariate approaches to uncover the genetic architecture of 23 anxiety-related phenotypes in 1636 F2 laboratory mice. We detected QTL with a genome-wide significance threshold of P < 0.05 on 14 chromosomes, of which 10 correspond to those identified by univariate analysis. Novel QTL were found on Chromosomes 3, 9, 13, and 17. Thus, multivariate analyses increased the yield of QTL exceeding a genome-wide significance threshold by 40%. On the basis of these results and by the application of a QTL estimator, we show that the mean number of QTL influencing anxiety-related behavior in mice is 6, with a 95% upper limit of 14.
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