Experimental Power for Indirect Effects in Group-randomized Studies with Group-level Mediators

Mediation analyses have provided a critical platform to assess the validity of theories of action across a wide range of disciplines. Despite widespread interest and development in these analyses, literature guiding the design of mediation studies has been largely unavailable. Like studies focused on the detection of a total or main effect, an important design consideration is the statistical power to detect indirect effects if they exist. Understanding the sensitivity to detect indirect effects is exceptionally important because it directly influences the scale of data collection and ultimately governs the types of evidence group-randomized studies can bring to bear on theories of action. However, unlike studies concerned with the detection of total effects, literature has not established power formulas for detecting multilevel indirect effects in group-randomized designs. In this study, we develop closed-form expressions to estimate the variance of and the power to detect indirect effects in group-randomized studies with a group-level mediator using two-level linear models (i.e., 2-2-1 mediation). The results suggest that when carefully planned, group-randomized designs may frequently be well positioned to detect mediation effects with typical sample sizes. The resulting power formulas are implemented in the R package PowerUpR and the PowerUp!-Mediator software (causalevaluation.org).     

The influence of emotion type,social value orientation and processing focus on approach-avoidance tendencies to negative dynamic facial expressions

Facial expressions of anger and fear have been seen to elicit avoidance behavior in the perceiver due to their negative valence. However, recent research uncovered discrepancies regarding these immediate motivational implications of fear and anger, suggesting that not all negative emotions trigger avoidance to a comparable extent. To clarify those discrepancies, we considered recent theoretical and methodological advances, and investigated the role of social preferences and processing focus on approach-avoidance tendencies (AAT) to negative facial expressions. We exposed participants to dynamic facial expressions of anger, disgust, fear, or sadness, while they processed either the emotional expression or the gender of the faces. AATs were assessed by reaction times of lever movements, and by posture changes via head-tracking. We found that—relative to angry faces-, fearful and sad faces triggered more approach, with a larger difference between fear and anger in prosocial compared to individualistic participants. Interestingly, these findings are in line with a recently developed concern hypothesis, suggesting that—relative to other negative expressions—expressions of distress may facilitate approach, especially in participants with prosocial preferences.     

Emotion perception from a componential perspective

The common conceptual understanding of emotion is that they are multi-componential, including subjective feelings, appraisals, psychophysiological activation, action tendencies, and motor expressions. Emotion perception, however, has traditionally been studied in terms of emotion labels, such as “happy”, which do not clearly indicate whether one, some, or all emotion components are perceived. We examine whether emotion percepts are multi-componential and extend previous research by using more ecologically valid, dynamic, and multimodal stimuli and an alternative response measure. The results demonstrate that observers can reliably infer multiple types of information (subjective feelings, appraisals, action tendencies, and social messages) from complex emotion expressions. Furthermore, this finding appears to be robust to changes in response items. The results are discussed in light of their implications for research on emotion perception.     

Subtyping obsessive-compulsive disorder: A taxometric analysis

Obsessive-compulsive disorder (OCD) is a heterogeneous condition comprising multiple symptoms. Researchers have identified OCD subtypes using a range of symptom-based research methods, including factor and cluster analyses and examination of differential treatment response. These methods can be challenged on the grounds that they fail to demonstrate the existence of discrete taxonomic entities. Furthermore, no study has examined subtyping on the basis of cognitive characteristics. In the present study, the categorical vs. dimensional status of 6 possible subtypes of OCD was examined using taxometric methods. Three potential cognitive subtypes (based on high levels of responsibility/threat estimation, perfectionism/certainty, and importance/control of thoughts) and 3 potential symptomatic subtypes (based on elevated levels of contamination obsessions and cleaning compulsions, checking, and obsessionality) were examined using the MAXEIG and MAMBAC procedures in a sample of 404 diagnosed cases of OCD. Findings favored dimensional models of the potential responsibility, perfectionism, checking, and contamination subtypes, but offered qualified support for taxonic models of the importance/control of thoughts and obsessional subtypes. Implications for the subclassification of OCD are discussed.     

隔代“亲”的社会心理解析

隔代抚育中出现了普遍的隔代“亲”现象。本文分别从文化传统（血缘宗亲）、心理需求、社会现实、补偿心理等几个方面来阐述隔代“亲”的成因。     

How checking as a cognitive style influences working memory performance

Compulsive checking is known to influence memory, yet there is little consideration of checking as a cognitive style within the typical population. We employed a working memory task where letters had to be remembered in their locations. The key experimental manipulation was to induce repeated checking after encoding by asking about a stimulus that had not been presented. We recorded the effect that such misleading probes had on a subsequent memory test. Participants drawn from the typical population but who scored highly on a checking‐scale had poorer memory and less confidence than low scoring individuals. While thoroughness is regarded as a quality, our results indicate that a cognitive style that favours repeated checking does not always lead to the best performance as it can undermine the authenticity of memory traces. This may affect various aspects of everyday life including the work environment and we discuss its implications and possible counter‐measures. Copyright © 2010 John Wiley & Sons, Ltd.     

Where to look first for an explanation of induction with uncertain categories

Recent research has examined how people predict unobserved features of an object when its category membership is ambiguous. The debate has focused on whether predictions are based solely on information from the most likely category, or whether information from other possible categories is also used. In the present experiment, we compared these category-based approaches with feature conjunction reasoning, where predictions are based on a comparison among exemplars (rather than categories) that share features with a target object. Reasoning strategies were assessed by examining patterns of feature prediction and by using an eye gaze measure of attention during induction. The main findings were (1) the majority of participants used feature conjunction rather than categorical strategies, (2) people predominantly gazed at the exemplars that were most similar to the target object, and (3) although people gazed most at the most probable category to which an object could belong, they also attended to other plausible category alternatives during induction. These findings question the extent to which category-based reasoning is used for induction when category membership is uncertain.     

Posttraumatic stress disorder following the September 11, 2001, terrorist attacks: a review of the literature among highly exposed populations

The September 11, 2001 (9/11), terrorist attacks were unprecedented in their magnitude and aftermath. In the wake of the attacks, researchers reported a wide range of mental and physical health outcomes, with posttraumatic stress disorder (PTSD) the one most commonly studied. In this review, we aim to assess the evidence about PTSD among highly exposed populations in the first 10 years after the 9/11 attacks. We performed a systematic review. Eligible studies included original reports based on the full Diagnostic and Statistical Manual of Mental Disorders (4th ed., rev.; American Psychiatric Association, 2000) criteria of PTSD among highly exposed populations such as those living or working within close proximity to the World Trade Center (WTC) and the Pentagon in New York City and Washington, DC, respectively, and first responders, including rescue, cleaning, and recovery workers. The large body of research conducted after the 9/11 attacks in the past decade suggests that the burden of PTSD among persons with high exposure to 9/11 was substantial. PTSD that was 9/11-related was associated with a wide range of correlates, including sociodemographic and background factors, event exposure characteristics, loss of life of significant others, and social support factors. Few studies used longitudinal study design or clinical assessments, and no studies reported findings beyond six years post-9/11, thus hindering documentation of the long-term course of confirmed PTSD. Future directions for research are discussed.     

Phantom arcs: now you see them..

A new visual illusion is reported and illustrated. The illusion, dubbed 'phantom arcs', survives manipulations of contrast, scale, and hue. The arcs can be seen in printed versions as well as in images displayed on CRT or LCD monitors. Data collected in an undergraduate perception class reveal that the illusion can be seen by untrained observers.