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).     

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.     

We remember the good things: Age differences in learning and memory

We combined a feedback-based learning task with a recognition memory paradigm to investigate how reward-based learning affects the event-related potential (ERP) correlates of recognition memory in younger and older adults. We found that positive, but not negative learning improves memory and results in an increased early ERP old–new effect, which is typically associated with familiarity-based memory. This indicates that reward-based learning supports a fast and relatively automatic memory retrieval process. Furthermore, we found age-related impairments in reward-based learning, whereas memory for the learned information was intact in the elderly, suggesting that declarative memory might be less affected by aging.     

The co-evolution of tools and minds: cognition and material culture in the hominin lineage

The structuring of our environment to provide cues and reminders for ourselves is common: We leave notes on the fridge, we have a particular place for our keys where we deposit them, making them easy to find. We alter our world to streamline our cognitive tasks. But how did hominins gain this capacity? What pushed our ancestors to structure their physical environment in ways that buffered thinking and began the process of using the world cognitively? I argue that the capacity to engage in these behaviours is a by-product of increased tool investment and tool curation, which in turn was necessary because of increasingly heterogeneous environments. The minute tools are carried and cared for, they begin to undergo selection for added functions, becoming available as cognitive primers and as signals. I explore the trajectory of this co-evolutionary feedback loop of hominins and their tools, and demonstrate the role tools have in shaping our thinking.     

Disregarding Preliminary Information When Rating Job Applicants' Performance: Mission Impossible?1

Firms allocate considerable resources to test job applicants' skills and to ensure that hiring decisions are nondiscriminatory. Interpreting selection output in light of preliminary information may undermine the impartiality of personnel selection decisions. In this study, human resource managers were presented preliminary information about a candidate's performance and asked to rate him according to a detailed assessment‐center report of his performance. We examined several interventions for reducing reliance on preliminary information: retrieving assessment‐center information, generating a rating model, or both. Participants (N = 167) excluded preliminary information from the interventions, but relied on it when rating the candidate. The documented failure to control for the effects of preliminary information on subsequent judgments can contribute to improved selection procedures.     

Two‐Step Testing in Employee Selection: Is score inflation a problem?

Unproctored Internet testing in employee selection has become increasingly popular over the past few years. However, there is a concern that cheating during unproctored administrations may influence the test results in terms of score inflation. The current research attempts to determine the extent of cheating on an unproctored Internet test of perceptual speed by analyzing data from a parallel version of the test administered in a proctored setting. Among a sample of 856 job applicants from nine European countries, there was no evidence that cheating occurred. In fact, evidence of an effect operating in the opposite direction was obtained. These results indicate that the use of unproctored Internet testing is appropriate for this type of test.