The Use of Propensity Scores in Mediation Analysis

Mediation analysis uses measures of hypothesized mediating variables to test theory for how a treatment achieves effects on outcomes and to improve subsequent treatments by identifying the most efficient treatment components. Most current mediation analysis methods rely on untested distributional and functional form assumptions for valid conclusions, especially regarding the relation between the mediator and outcome variables. Propensity score methods offer an alternative whereby the propensity score is used to compare individuals in the treatment and control groups who would have had the same value of the mediator had they been assigned to the same treatment condition. This article describes the use of propensity score weighting for mediation with a focus on explicating the underlying assumptions. Propensity scores have the potential to offer an alternative estimation procedure for mediation analysis with alternative assumptions from those of standard mediation analysis. The methods are illustrated investigating the mediational effects of an intervention to improve sense of mastery to reduce depression using data from the Job Search Intervention Study (JOBS II). We find significant treatment effects for those individuals who would have improved sense of mastery when in the treatment condition but no effects for those who would not have improved sense of mastery under treatment.     

Developmental Systems Theory Formulated as a Claim about Inherited Representations*

Developmental systems theory (DST) is often dismissed on the basis that the causal indispensability of nongenetic factors in evolution and development has long been appreciated. A reformulation makes a more substantive claim: that the special role played by genes is also played by some (but not all) nongenetic resources. That special role can be captured by Shea's 'inherited representation'. Formulating DST as the claim that there are nongenetic inherited representations turns it into a striking, empirically testable hypothesis. DST's characteristic rejection of a gene versus environment dichotomy is preserved but without dissolving into an interactionist casual soup, as some have alleged.     

Chilean validation of the Posttraumatic Stress Disorder Checklist-Civilian version (PCL-C) after the earthquake on February 27, 2010

Posttraumatic stress disorder (PTSD) is an anxiety disorder in which an individual re-experiences a traumatic event, avoids situations related to it, and shows excessive arousal. The disorder appears after experiencing a life-threatening event, such as a war or a natural disaster. Thus, the validation of tests which assess the disorder after the earthquake on February 27, 2010, in Chile is crucial for its evaluation and subsequent intervention. The present study includes psychometric data for the Posttraumatic Stress Disorder Checklist-Civilian version (PCL-C) on a sample of 509 survivors of the disaster. Values indicate good psychometric properties of the questionnaire.     

The role of defeat and entrapment in depression, anxiety, and suicide

Defeat and entrapment are psychological constructs that have played a central role in evolutionary accounts of depression. These concepts have since been implicated in theoretical accounts of anxiety disorders and suicidality. The current article reports on a systematic review of the existing research investigating the links among defeat, entrapment, and psychopathology in the domains of depression, suicidality, posttraumatic stress disorder (PTSD), and other anxiety syndromes. Fifty-one original research articles were identified and critically reviewed. There was strong convergent evidence for a link with depressive symptoms, across a variety of clinical and nonclinical samples. Preliminary support for an association with suicidality was also observed, with effects not readily explainable in terms of comorbid depression. There was strong evidence for an association between defeat and PTSD, although this may have been partly accounted for by comorbid depression. The findings for other anxiety disorders were less consistent. There was, however, evidence that social anxiety in individuals with psychosis may be related to perceptions of entrapment. Overall, there was evidence that perceptions of defeat and entrapment were closely associated with various forms of human psychopathology. These effects were often in the moderate to large range and superseded the impact of other environmental and psychological stressors on psychopathology. We provide a unified theoretical model of how defeat and entrapment may contribute to these different psychopathological conditions. Clinical implications and avenues for future research are discussed.     

Desensitization to media violence: links with habitual media violence exposure, aggressive cognitions, and aggressive behavior

This study examined the links between desensitization to violent media stimuli and habitual media violence exposure as a predictor and aggressive cognitions and behavior as outcome variables. Two weeks after completing measures of habitual media violence exposure, trait aggression, trait arousability, and normative beliefs about aggression, undergraduates (N = 303) saw a violent film clip and a sad or a funny comparison clip. Skin conductance level (SCL) was measured continuously, and ratings of anxious and pleasant arousal were obtained after each clip. Following the clips, participants completed a lexical decision task to measure accessibility of aggressive cognitions and a competitive reaction time task to measure aggressive behavior. Habitual media violence exposure correlated negatively with SCL during violent clips and positively with pleasant arousal, response times for aggressive words, and trait aggression, but it was unrelated to anxious arousal and aggressive responding during the reaction time task. In path analyses controlling for trait aggression, normative beliefs, and trait arousability, habitual media violence exposure predicted faster accessibility of aggressive cognitions, partly mediated by higher pleasant arousal. Unprovoked aggression during the reaction time task was predicted by lower anxious arousal. Neither habitual media violence usage nor anxious or pleasant arousal predicted provoked aggression during the laboratory task, and SCL was unrelated to aggressive cognitions and behavior. No relations were found between habitual media violence viewing and arousal in response to the sad and funny film clips, and arousal in response to the sad and funny clips did not predict aggressive cognitions or aggressive behavior on the laboratory task. This suggests that the observed desensitization effects are specific to violent content.     

Stability and change of personality across the life course: the impact of age and major life events on mean-level and rank-order stability of the Big Five

Does personality change across the entire life course, and are those changes due to intrinsic maturation or major life experiences? This longitudinal study investigated changes in the mean levels and rank order of the Big Five personality traits in a heterogeneous sample of 14,718 Germans across all of adulthood. Latent change and latent moderated regression models provided 4 main findings: First, age had a complex curvilinear influence on mean levels of personality. Second, the rank-order stability of Emotional Stability, Extraversion, Openness, and Agreeableness all followed an inverted U-shaped function, reaching a peak between the ages of 40 and 60 and decreasing afterward, whereas Conscientiousness showed a continuously increasing rank-order stability across adulthood. Third, personality predicted the occurrence of several objective major life events (selection effects) and changed in reaction to experiencing these events (socialization effects), suggesting that personality can change due to factors other than intrinsic maturation. Fourth, when events were clustered according to their valence, as is commonly done, effects of the environment on changes in personality were either overlooked or overgeneralized. In sum, our analyses show that personality changes throughout the life span, but with more pronounced changes in young and old ages, and that this change is partly attributable to social demands and experiences.     

Adaptive memory: Stereotype activation is not enough

Studies have shown that survival processing leads to superior memorability. The aim of the present study was to examine whether this survival recall advantage might result from stereotype activation. To test this hypothesis, we conducted a pilot study and two experiments in which participants were primed with stereotypes (Experiment 1, professor and elderly person; Experiment 2, survival-stereotype). In Experiment 1, 120 undergraduates were randomly assigned to a survival, professor stereotype, elderly person stereotype, or moving scenario and rated words for their relevance to the imagined scenario. In Experiment 2, 75 undergraduates were given a survival, survival-stereotype (based on our pilot study), or moving scenario. Both experiments showed that survival processing leads to a greater recall advantage over the stereotype groups and control group. These data indicate that the mere activation of stereotypes cannot explain the survival recall advantage.     

Disambiguating Information and Memory Resources in Children’s Processing of Italian Relative Clauses

We investigated the role of number agreement on verb and of animacy in the comprehension of subject and object relative clauses in 51 monolingual Italian-speaking children, mean age 9:33, tested through a self-paced listening experiment with a final comprehension question. A digit span test and a listening span test were also administered to examine the role of memory in comprehension. Subject relative clauses were easier to comprehend than object relative clauses; animacy of the relative clause head improved comprehension of object relative clauses; memory, as measured by the digit span test, modulates comprehension of object relative clauses, both with animate and inanimate heads, as shown in response accuracy. Although all children process number agreement morphology on the verb, only some perform a correct reanalysis, as shown by the accuracy measures. We argue that number agreement disambiguation is particularly taxing for children, as it provides a negative symptom in the sense of Fodor and Inoue (J Psycholinguist Res 29(1):25–36, 2000) and reanalysis requires them to hold two dependencies in memory.     

Processing of a Free Word Order Language: The Role of Syntax and Context

In languages with flexible constituent order (so-called free word order languages), available orders are used to encode given/new distinctions; they therefore differ not only syntactically, but also in their context requirements. In Experiment 1, using a self-paced reading task, we compared Russian S V IO DO (canonical), DO S V IO and DO IO V S constructions in appropriate vs. inappropriate contexts (those that violated their context requirements). The context factor was significant, while the syntax factor was not. The less pronounced context effect evidenced in previous studies (e.g., Kaiser and Trueswell in Cognitioin 94:113–147, 2004) might be due to the use of shorter target sentences and less extensive contexts. We also demonstrated that the slow-down starts at the first contextually inappropriate constituent, which shows that the information about context requirements is taken into account immediately, but that it develops faster on preverbal subjects and postverbal indirect objects (occupying their canonical positions) than on preverbal indirect objects (occupying a noncanonical position, or scrambled). In Experiment 2, these findings were replicated for IO S V DO and IO DO V S orders. S V IO DO orders with a continuation were used to show that there is no additional effect of inappropriate context at the end of the sentence.