Effect of non-normality on test statistics for one-way independent groups designs

The data obtained from one‐way independent groups designs is typically non‐normal in form and rarely equally variable across treatment populations (i.e. population variances are heterogeneous). Consequently, the classical test statistic that is used to assess statistical significance (i.e. the analysis of variance F test) typically provides invalid results (e.g. too many Type I errors, reduced power). For this reason, there has been considerable interest in finding a test statistic that is appropriate under conditions of non‐normality and variance heterogeneity. Previously recommended procedures for analysing such data include the James test, the Welch test applied either to the usual least squares estimators of central tendency and variability, or the Welch test with robust estimators (i.e. trimmed means and Winsorized variances). A new statistic proposed by Krishnamoorthy, Lu, and Mathew, intended to deal with heterogeneous variances, though not non‐normality, uses a parametric bootstrap procedure. In their investigation of the parametric bootstrap test, the authors examined its operating characteristics under limited conditions and did not compare it to the Welch test based on robust estimators. Thus, we investigated how the parametric bootstrap procedure and a modified parametric bootstrap procedure based on trimmed means perform relative to previously recommended procedures when data are non‐normal and heterogeneous. The results indicated that the tests based on trimmed means offer the best Type I error control and power when variances are unequal and at least some of the distribution shapes are non‐normal.     

Body image, shape, and volumetric assessments using 3D whole body laser scanning and 2D digital photography in females with a diagnosed eating disorder: preliminary novel findings

We piloted three-dimensional (3D) body scanning in eating disorder (ED) patients. Assessments of 22 ED patients (including nine anorexia nervosa (AN) patients, 12 bulimia nervosa (BN) patients, and one patient with eating disorder not otherwise specified) and 22 matched controls are presented. Volunteers underwent visual screening, two-dimensional (2D) digital photography to assess perception and dissatisfaction (via computerized image distortion), and adjunctive 3D full-body scanning. Patients and controls perceived themselves as bigger than their true shape (except in the chest region for controls and anorexia patients). All participants wished to be smaller across all body regions. Patients had poorer veridical perception and greater dissatisfaction than controls. Perception was generally poorer and dissatisfaction greater in bulimia compared with anorexia patients. 3D-volume:2D-area relationships showed that anorexia cases had least tissue on the torso and most on the arms and legs relative to frontal area. The engagement of patients with the scanning process suggests a validation study is viable. This would enable mental constructs of body image to be aligned with segmental volume of body areas, overcoming limitations, and errors associated with 2D instruments restricted to frontal (coronal) shapes. These novel data could inform the design of clinical trials in adjunctive treatments for eating disorders.     

Individual differences in adolescents' sympathetic and parasympathetic functioning moderate associations between family environment and psychosocial adjustment

The present study tested whether individual differences in autonomic nervous system functioning interact with environmental risk factors to predict adolescents' psychosocial functioning. The authors assessed skin conductance and respiratory sinus arrhythmia at rest and during laboratory stressors in 110 14-year-olds. Subsequently, adolescents and their mothers provided both questionnaire and daily diary data (over 10 days) on emotional and interpersonal functioning. The authors found stronger associations between environmental risk factors (having a single-mother household or a mother with high internalizing problems) and psychosocial outcomes (externalizing problems, daily negative affect, and daily interaction quality) among youths with specific patterns of tonic and stress-induced sympathetic and parasympathetic nervous system activity, but the pattern of moderating effects differed between boys and girls. The findings support the notion that individual differences in autonomic functioning index variation in youth's susceptibility to environmental risk factors.     

Multiple trials may yield exaggerated effect size estimates

Published psychological research attempting to support the existence of small and medium effect sizes may not have enough participants to do so accurately, and thus, repeated trials or the use of multiple items may be used in an attempt to obtain significance. Through a series of Monte-Carlo simulations, this article describes the results of multiple trials or items on effect size estimates when the averages and aggregates of a dependent measure are analyzed. The simulations revealed a large increase in observed effect size estimates when the numbers of trials or items in an experiment were increased. Overestimation effects are mitigated by correlations between trials or items, but remain substantial in some cases. Some concepts, such as a P300 wave or a test score, are best defined as a composite of measures. Troubles may arise in more exploratory research where the interrelations among trials or items may not be well described.     

Errors in identifying and expressing emotion in facial expressions, voices, and postures unique to social anxiety

The purpose of the present study was to see if 7-10-year-old socially anxious children (n = 26) made systematic errors in identifying and sending emotions in facial expressions, paralanguage, and postures as compared with the more random errors of children who were inattentive-hyperactive (n = 21). It was found that socially anxious children made more errors in identifying anger and fear in children's facial expressions and anger in adults' postures and in expressing anger in their own facial expressions than did their inattentive-hyperactive peers. Results suggest that there may be systematic difficulties specifically in visual nonverbal emotion communication that contribute to the personal and social difficulties socially anxious children experience.     

Deontic and epistemic reasoning in children

It is widely accepted that adults show an advantage for deontic over epistemic reasoning. Two published studies (Cummins, 1996b; Harris and Núñez, 1996, Experiment 4) found evidence of this “deontic advantage” in preschool-aged children and are frequently cited as evidence that preschoolers show the same deontic advantage as adults. However, neither study has been replicated, and it is not clear from either study that preschoolers were showing the deontic advantage under the same conditions as adults. The current research investigated these issues. Experiment 1 attempted to replicate both Cummins’s and Harris and Núñez’s studies with 3- and 4-year-olds (N = 56), replicating the former with 4-year-olds and the latter with both 3- and 4-year-olds. Experiment 2 modified Cummins’s task to remove the contextual differences between conditions, making it more similar to adult tasks, finding that 4-year-olds (n = 16) show no evidence of the deontic advantage when no authority figure is present in the deontic condition, whereas both 7-year-olds (n = 16) and adults (n = 28) do. Experiment 3 removed the authority figure from the deontic condition in Harris and Núñez’s task, again finding that 3- and 4-year-olds (N = 28) show no evidence of the deontic advantage under these conditions. These results suggest that for preschoolers, the deontic advantage is reliant on particular contextual cues such as the presence of an authority figure, in the deontic condition. By 7 years of age, however, children are reasoning like adults and show evidence of the advantage when no such contextual cues are present.     

Memory for multiple visual ensembles in infancy

The number of individual items that can be maintained in working memory is limited. One solution to this problem is to store representations of ensembles that contain summary information about large numbers of items (e.g., the approximate number or cumulative area of a group of many items). Here we explored the developmental origins of ensemble representations by asking whether infants represent ensembles and, if so, how many at one time. We habituated 9-month-old infants to arrays containing 2, 3, or 4 spatially intermixed colored subsets of dots, then asked whether they detected a numerical change to one of the subsets or to the superset of all dots. Experiment Series 1 showed that infants detected a numerical change to 1 of the subsets when the array contained 2 subsets but not 3 or 4 subsets. Experiment Series 2 showed that infants detected a change to the superset of all dots no matter how many subsets were presented. Experiment 3 showed that infants represented both the approximate number and the cumulative surface area of these ensembles. Our results suggest that infants, like adults (Halberda, Sires, & Feigenson, 2006), can store quantitative information about 2 subsets plus the superset: a total of 3 ensembles. This converges with the known limit on the number of individual objects infants and adults can store and suggests that, throughout development, an ensemble functions much like an individual object for working memory.     

Depression, anxiety, and the MCMI-III: construct validity and diagnostic efficiency

This study aimed to enhance knowledge of the construct validity and diagnostic efficiency of the depression- and anxiety-related scales of the MCMI-III (Millon, 1994). The MCMI-III, various concurrent depression and anxiety measures, and an Axis I structured diagnostic interview were administered in a total sample of 696 outpatients with depressive disorders, anxiety disorders, or both. Sound construct validity was found for the Dysthymia and Major Depression clinical syndrome scales and the Avoidant and Depressive personality disorder scales. The validity of the Anxiety scale was poor, showing moderate convergence with panic and worry-related anxiety measures, but problems discriminating from depression. Operating characteristics for discriminating depressed patients from anxious patients were fair for the Major Depression scale, but poor for the Anxiety and Dysthymia scales.     

What You Feel Influences What You See: The Role of Affective Feelings in Resolving Binocular Rivalry

It seems obvious that what you see influences what you feel, but what if the opposite were also true? What if how you feel can shape your visual experience? In this experiment, we demonstrate that the affective state of a perceiver influences the contents of visual awareness. Participants received positive, negative, and neutral affect inductions and then completed a series of binocular rivalry trials in which a face (smiling, scowling, or neutral) was presented to one eye and a house to the other. The percepts “competed” for dominance in visual consciousness. We found, as predicted, that all faces (smiling, scowling, and neutral) were dominant for longer when perceivers experienced unpleasant affect compared to when they were in a neutral state (a social vigilance effect), although scowling faces increased their dominance when perceivers felt unpleasant (a relative negative congruence effect). Relatively speaking, smiling faces increased their dominance more when perceivers were experiencing pleasant affect (a positive congruence effect). These findings illustrate that the affective state of a perceiver serves as a context that influences the contents of consciousness.     

Seeing failure in your life: Imagery perspective determines whether self-esteem shapes reactions to recalled and imagined failure

The present research reveals that when it comes to recalling and imagining failure in one's life, changing how one looks at the event can change its impact on well-being; however, the nature of the effect depends on an aspect of one's self-concept, namely, self-esteem. Five studies measured or manipulated the visual perspective (internal first-person vs. external third-person) individuals used to mentally image recalled or imagined personal failures. It has been proposed that imagery perspective determines whether people's reactions to an event are shaped bottom-up by concrete features of the event (first-person) or top-down by their self-concept (third-person; L. K. Libby & R. P. Eibach, 2011b). Evidence suggests that differences in the self-concepts of individuals with low and high self-esteem (LSEs and HSEs) are responsible for self-esteem differences in reaction to failure, leading LSEs to have more negative thoughts and feelings about themselves (e.g., M. H. Kernis, J. Brockner, & B. S. Frankel, 1989). Thus, the authors predicted, and found, that low self-esteem was associated with greater overgeneralization--operationalized as negativity in accessible self-knowledge and feelings of shame--only when participants had pictured failure from the third-person perspective and not from the first-person. Further, picturing failure from the third-person, rather than first-person, perspective, increased shame and the negativity of accessible knowledge among LSEs, whereas it decreased shame among HSEs. Results help to distinguish between different theoretical accounts of how imagery perspective functions and have implications for the study of top-down and bottom-up influences on self-judgment and emotion, as well as for the role of perspective and abstraction in coping.