Left-handedness in twin families: support of an environmental hypothesis

Information on handedness, assessed as writing-hand, was collected from 197 MZ twin pairs and 203 DZ twin pairs and from their parents, spouses, and children. Associations for pairs of relatives were studied by 2 X 2 tables, computing chi squared-values and tetrachoric correlations. Correlations of about .3 were obtained for mother-offspring and sibling pairs, while for cousins the correlation was .25 (in a small sample). No other significant associations were found, not even for twins. These results suggest only a small, if any, genetic effect, and only a small environmental between family effect, most of which seems to be a maternal effect. The lack of cotwin correlations and correlations for one of the twins with her/his ordinary brothers/sisters suggest the existence of an effect specific to twins, since the correlation for pairs of ordinary siblings is significant. Conclusions drawn from twin studies alone may be biased. The frequency of left-hand writers has increased from 1% to 10% in the different age groups born during the last century in Norway. This age effect is present mainly in hand writing and not so much in handedness generally, suggesting a decrease in cultural repression against left-hand writing.     

Realism and Empirical Equivalence

Journal of Philosophical Logic - The main purpose of this paper is to investigate various notions of empirical equivalence in relation to the two main arguments for realism in the philosophy of...     

Factorial structure and invariance across gender of the Swedish self-consciousness scale

In this study, I tested different factor models and the factorial invariance across gender for the Self-Consciousness Scale (Fenigstein, Scheier, & Buss (1975) using confirmatory factor analyses. University students (251 women and 259 men) completed the Swedish version of the scale. A respecified (Item 15 loading on the factor Internal State Awareness [ISA] instead of on the factor Self-Reflection [SR]) 17-item, 4-factor model of Burnkrant and Page (1984) including the factors SR, ISA, Public Self-Consciousness, and Social Anxiety demonstrated the best fit for both men and women. Factor intercorrelations were overall stronger for women. The respecified model demonstrated factorial invariance across gender. I discuss the strengthening of scale reliability through the expansion of subscale items and invariance testing across groups.     

Using individual differences to predict job performance: correcting for direct and indirect restriction of range

The present study investigates the relationship between individual differences, indicated by personality (FFM) and general mental ability (GMA), and job performance applying two different methods of correction for range restriction. The results, derived by analyzing meta-analytic correlations, show that the more accurate method of correcting for indirect range restriction increased the operational validity of individual differences in predicting job performance and that this increase primarily was due to general mental ability being a stronger predictor than any of the personality traits. The estimates for single traits can be applied in practice to maximize prediction of job performance. Further, differences in the relative importance of general mental ability in relation to overall personality assessment methods was substantive and the estimates provided enables practitioners to perform a correct utility analysis of their overall selection procedure.     

Criterion Validity is Maintained When Items are Evaluatively Neutralized: Evidence from a Full‐scale Five‐factor Model Inventory

The original version and an evaluatively neutralized version (with items rephrased to reduce popularity) of a personality inventory were compared. The results revealed (i) similar criterion validity across three different sets of self‐rated behaviours, (ii) stronger relations to the rated social desirability of criteria for the original version and (iii) less correlation between factors for the neutralized version. We take the results to indicate that evaluative neutralization is a viable technique for reducing social desirability in self‐ratings. Implications for test construction are discussed. Copyright © 2014 European Association of Personality Psychology     

To adjust or not adjust: Nonparametric effect sizes,confidence intervals,and real-world meaning

ObjectivesThe main objectives of this article are to: (a) investigate if there are any meaningful differences between adjusted and unadjusted effect sizes (b) compare the outcomes from parametric and non-parametric effect sizes to determine if the potential differences might influence the interpretation of results, (c) discuss the importance of reporting confidence intervals in research, and discuss how to interpret effect sizes in terms of practical real-world meaning.DesignReview.MethodA review of how to estimate and interpret various effect sizes was conducted. Hypothetical examples were then used to exemplify the issues stated in the objectives.ResultsThe results from the hypothetical research designs showed that: (a) there is a substantial difference between adjusted and non-adjusted effect sizes especially in studies with small sample sizes, and (b) there are differences in outcomes between the parametric and non-parametric effect size formulas that may affect interpretations of results.ConclusionsThe different hypothetical examples in this article clearly demonstrate the importance of treating data in ways that minimize potential biases and the central issues of how to discuss the meaningfulness of effect sizes in research.