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).     

MATERNAL TRAUMA AFFECTS PRENATAL MENTAL HEALTH AND INFANT STRESS REGULATION AMONG PALESTINIAN DYADS

We examined how diverse and cumulated traumatic experiences predicted maternal prenatal mental health and infant stress regulation in war conditions and whether maternal mental health mediated the association between trauma and infant stress regulation. Participants were 511 Palestinian mothers from the Gaza Strip who reported exposure to current war trauma (WT), past childhood emotional (CEA) and physical abuse, socioeconomic status (SES), prenatal mental health problems (posttraumatic stress disorder and depression symptoms), and perceived stress during their secondtrimester of pregnancy as well as infant stress regulation at 4 months. While all trauma types were associated with high levels of prenatal symptoms, CEA had the most wide‐ranging effects and was uniquely associated with depression symptoms. Concerning infant stress regulation, mothers’ CEA predicted negative affectivity, but only among mothers with low WT. Against hypothesis, the effects of maternal trauma on infant stress regulation were not mediated by mental health symptoms. Mothers’ higher SES was associated with better infant stress regulation whereas infant prematurity and male sex predisposed for difficulties. Our findings suggest that maternal childhood abuse, especially CEA, should be a central treatment target among war‐exposed families. Cumulated psychosocial stressors might increase the risk for transgenerational problems.     

MOTHER–CHILD AND FATHER–CHILD PLAY INTERACTION: THE IMPORTANCE OF PARENTAL PLAYFULNESS AS A MODERATOR OF THE LINKS BETWEEN PARENTAL BEHAVIOR AND CHILD NEGATIVITY

Based on the premise that father–child play is an important context for children's development and that fathers “specialize” in play, similarities and differences in the role of playfulness in the father–child and mother–child relationship were examined. Participants in this study included 111 families (children's age: 1–3 years). Father–child and mother–child play interactions were videotaped and coded for parental playfulness, sensitivity, structuring, and nonintrusiveness as well as child negativity. Results indicated that mothers and fathers did not differ in playfulness and that mothers and fathers who were higher in playfulness had children with lower levels of negativity. However, playfulness differently moderated the links between parents’ and children's behaviors for mothers and fathers. A double‐risk pattern was found for mothers, such that the links between child negativity and maternal sensitivity, structuring, and nonintrusiveness were significant only for the subgroup of mothers with low levels of playfulness. When mothers had high levels of playfulness, these effects were negligible. For fathers, a double‐buffer pattern was revealed, indicating that the links between child negativity and paternal sensitivity and structuring were significant only for fathers with high levels of playfulness. When fathers had low levels of playfulness, these effects were negligible. These findings demonstrate the important role that parental playfulness has on parent–child interaction as well as the need to examine moderation patterns separately for fathers and mothers.     

第二语言阅读“熔断”假说的认知心理证据:在线篇章处理的范式

本研究以认知心理学的结构建造理论为实验框架,模拟学习者母语及外语在线篇章处理的过程,从而获取第二语言阅读"熔断"假说以及"门槛"效应的认知心理证据。英语水平差别显著的高低两组共60名被试参加了英、汉语故事理解加工实验,考察他们如何对故事的人物角色进行持续跟踪,以厘清故事内的"因果链"。结果发现:(1)高水平组成功地把他们的母语故事理解加工能力迁移到第二语言的故事理解加工,而低水平组则迁移失败;(2)理解加工能力的迁移与被试心理表征建构能力以及抑制机制的效率紧密关联,高水平组被试能有效地利用抑制机制来管理他们第二语言的结构建造过程,从而建立对故事的连贯心理表征,而低水平组则不能。在分析上述结果的基础上,文章提出第二语言阅读"熔断"假说的认知心理证据就是第二语言心理表征建构与抑制机制的作用问题;要成功地进行第二语言篇章理解,读者必须要使其二语潜在的能力(如词汇效率等)发展到某个点上,使得与抑制(结构建造的关键)相关的许多无意识的决定过程能够高度自动化。     

Because difficulty is not the same for everyone: the impact of complexity in working memory is associated with cannabinoid 1 receptor genetic variation in young adults

Individual differences in working memory ability are mainly revealed when a demanding challenge is imposed. Here, we have associated cannabinoid 1 (CB1) receptor genetic variation rs2180619 (AA, AG, GG), which is located in a potential CNR1 regulatory sequence, with performance in working memory. Two-hundred and nine Mexican-mestizo healthy young participants (89 women, 120 men, mean age: 23.26 years, SD?=?2.85) were challenged to solve a medium (2-back) vs. a high (3-back) difficulty N-back tasks. All subjects responded as expected, performance was better with the medium than the high demand task version, but no differences were found among genotypes while performing each working memory (WM) task. However, the cost of the level of complexity in N-back paradigm was double for GG subjects than for AA subjects. It is noteworthy that an additive-dosage allele relation was found for G allele in terms of cost of level of complexity. These genetic variation results support that the endocannabinoid system, evaluated by rs2180619 polymorphism, is involved in WM ability in humans.     

2型糖尿病大血管病变机理和糖尿病治疗

2型糖尿病大血管病变与代谢综合征密切相关.现代医学认为两者的根本原因是胰岛素抵抗,导致糖耐量下降,血脂紊乱,高胰岛素血症,高血压和高凝状态等.从系统论的观点阐述了代谢综合征的相互关系和2型糖尿病大血管病变发病机理,并进一步从该观点阐明2型糖尿病的防治策略.