Rediscovering the Individual in Mediation Analyses

Using the article by von Eye and colleagues as a springboard, this commentary considers a variety of challenges to valid exploration of mediation processes. Along the way, a several alternatives for reinserting the individual back into mediation processes are entertained. The configural frequency approach to mediation analyses proposed by von Eye et al. (Integrative Psychological & Behavioral Science 43(3), 2009) represents a major step toward this objective. Idiographic approaches are proposed as the next step in the progression toward individual-centered mediation analyses.

What Carries a Mediation Process? Configural Analysis of Mediation

Mediation is a process that links a predictor and a criterion via a mediator variable. Mediation can be full or partial. This well-established definition operates at the level of variables even if they are categorical. In this article, two new approaches to the analysis of mediation are proposed. Both of these approaches focus on the analysis of categorical variables. The first involves mediation analysis at the level of configurations instead of variables. Thus, mediation can be incorporated into the arsenal of methods of analysis for person-oriented research. Second, it is proposed that Configural Frequency Analysis (CFA) can be used for both exploration and confirmation of mediation relationships among categorical variables. The implications of using CFA are first that mediation hypotheses can be tested at the level of individual configurations instead of variables. Second, this approach leaves the door open for different types of mediation processes to exist within the same set. Using a data example, it is illustrated that aggregate-level analysis can overlook mediation processes that operate at the level of individual configurations.     

Mediation analysis and categorical variables: The final frontier

Many scholars are interested in understanding the process by which an independent variable affects a dependent variable, perhaps in part directly and perhaps in part indirectly, occurring through the activation of a mediator. Researchers are facile at testing for mediation when all the variables are continuous, but a definitive answer had been lacking heretofore as to how to analyze the data when the mediator or dependent variable is categorical. This paper describes the problems that arise as well as the potential solutions. In the end, a solution is recommended that is both optimal in its statistical qualities as well as practical and easily implemented: compute z_Mediation.     

Assessing Omitted Confounder Bias in Multilevel Mediation Models

To draw valid inference about an indirect effect in a mediation model, there must be no omitted confounders. No omitted confounders means that there are no common causes of hypothesized causal relationships. When the no-omitted-confounder assumption is violated, inference about indirect effects can be severely biased and the results potentially misleading. Despite the increasing attention to address confounder bias in single-level mediation, this topic has received little attention in the growing area of multilevel mediation analysis. A formidable challenge is that the no-omitted-confounder assumption is untestable. To address this challenge, we first analytically examined the biasing effects of potential violations of this critical assumption in a two-level mediation model with random intercepts and slopes, in which all the variables are measured at Level 1. Our analytic results show that omitting a Level 1 confounder can yield misleading results about key quantities of interest, such as Level 1 and Level 2 indirect effects. Second, we proposed a sensitivity analysis technique to assess the extent to which potential violation of the no-omitted-confounder assumption might invalidate or alter the conclusions about the indirect effects observed. We illustrated the methods using an empirical study and provided computer code so that researchers can implement the methods discussed.     

Mediation with categorical variables compleat

This rejoinder addresses the thoughtful issues raised by the commentators. We hold to the analytical solution of fitting X → M (to obtain a and sa) and X&;M→ (to obtain b and sb) via regression or logistic regression, depending on whether M and Y are continuous or categorical. Then researchers compute za, zb, and ZMediation.     

Exploratory Mediation Analysis of Dichotomous Outcomes via Regularization

Abstract

Exploratory mediation analysis via regularization, or XMed, is a recently developed technique that allows one to identify potential mediators of a process of interest. However, as currently implemented, it can only be applied to continuous outcomes. We extend this method to allow application to dichotomous outcomes, including both mediators and dependent variables. Simulation results show that XMed can achieve the same sensitivity as more conventional methods for mediation analysis such as the Sobel test, percentile bootstrap, and bias-corrected bootstrap, but in general requires only half the sample size to do so. We demonstrate the implementation of this approach using an illustrative example examining the relationship between youth behavioral/emotional problems and alcohol use.     

Mediation analysis and categorical variables: Some further frontiers

Iacobucci (2012) provides a conceptually appealing, readily implemented measure to assess mediation for a far wider range of data type combinations than traditional OLS-based analyses permit. Here, we consider potential applications and extensions along several lines, particularly in terms of random utility models, simulation-based estimation, and potential nonlinearities, as well as some methodological and cultural impediments.     

Commentary on “Mediation analysis and categorical variables: The final frontier” by Dawn Iacobucci

The commentary discusses several topics in Dr. Iacobucci's article on mediation analysis with categorical variables including the lack of equivalency of mediated effect measures, ab, and c–c′, that are algebraically equivalent in ordinary least squares regression models. The commentary raises the issue of correlated mediation coefficients and presents formulas to include the correlation in the test of significance. References to new developments in causal mediation analysis for categorical variables are given and the importance of programs of research to establish a mediation theory is emphasized.     

高职生因果定向与学业表现的关系

为了考察高职生因果定向的特点及因果定向与学生学业表现(学业成绩和专业技能)的关系。该研究以修订的一般因果定向量表为工具,在济南和淄博的三所高职抽取505名学生作为被试进行调查。结果发现:1)修订后的一般因果定向量表具有良好的信效度;2)高职生在因果定向的三个维度上得分差异显著,由高到低依次为自主定向、控制定向和非个人定向;3)自主定向显著正向预测学业表现,控制定向显著负向预测学业表现,而非个人定向对学业表现的预测作用不显著。我国高职生与国外被试的因果定向特点基本一致,说明因果定向具有一定的文化普适性。同时,不同因果定向对学业表现具有不同的预测作用,教育者有必要对学生进行因果定向的教育和引导。     

Estimation of Controlled Direct Effects in Longitudinal Mediation Analyses with Latent Variables in Randomized Studies

Abstract

In a randomized study with longitudinal data on a mediator and outcome, estimating the direct effect of treatment on the outcome at a particular time requires adjusting for confounding of the association between the outcome and all preceding instances of the mediator. When the confounders are themselves affected by treatment, standard regression adjustment is prone to severe bias. In contrast, G-estimation requires less stringent assumptions than path analysis using SEM to unbiasedly estimate the direct effect even in linear settings. In this article, we propose a G-estimation method to estimate the controlled direct effect of treatment on the outcome, by adapting existing G-estimation methods for time-varying treatments without mediators. The proposed method can accommodate continuous and noncontinuous mediators, and requires no models for the confounders. Unbiased estimation only requires correctly specifying a mean model for either the mediator or the outcome. The method is further extended to settings where the mediator or outcome, or both, are latent, and generalizes existing methods for single measurement occasions of the mediator and outcome to longitudinal data on the mediator and outcome. The methods are utilized to assess the effects of an intervention on physical activity that is possibly mediated by motivation to exercise in a randomized study.     

Individual differences in religiosity as a function of cognitive ability and cognitive style

The current study examines the degree to which individual differences in cognitive ability and cognitive style (rational thinking vs. experiential thinking) uniquely and jointly account for differences in religiosity. Using an array of measures of religiosity, results show that cognitive ability has a medium to large negative effect on various aspects of religiosity. Though also negatively related to religiosity, rational thinking style did not add significant unique effects, nor did it convey a significant indirect effect from cognitive ability. Experiential thinking was generally unrelated to ability but was positively related to some aspects of religiosity. Overall the results confirm that those with higher cognitive ability are less likely to accept religious doctrine or engage in religious behaviors and those with lower ability are more likely to accept religious doctrine and exhibit higher levels of fundamentalism. Cognitive style appears to play a lesser role in explaining individual differences in religiosity than cognitive ability.     

Individual differences in (non-visual) processing style predict the face inversion effect

Recent research suggests that individuals with relatively weak global precedence (i.e., a smaller propensity to view visual stimuli in a configural manner) show a reduced face inversion effect (FIE). Coupled with such findings, a number of recent studies have demonstrated links between an advantage for feature-based processing and the presentation of traits associated with autism among the general population. The present study sought to bridge these findings by investigating whether a relationship exists between the possession of autism-associated traits (i.e., as indicated by individuals'"autism quotient" [(AQ) and the size of the FIE. Participants completed an on-line study in which the AQ was measured prior to a standard face recognition task where half of the faces were inverted at test. The results confirmed that higher AQ levels were predictive of smaller FIEs. Implications for a common underlying factor relating to processing orientation are discussed.     

The prospective relationship between child personality and perceived parenting: Mediation by parental sense of competence

This study examined the prospective relationship between childhood Big Five personality characteristics and perceived parenting in adolescence. In addition, we investigated whether this relationship was mediated by parental sense of competence, and whether associations were different for mothers and fathers. For 274 children, teachers reported on children’s Big Five personality characteristics at Time 1, mothers and fathers reported on their sense of competence at Time 2, and the children (who had now become adolescents) rated their parents’ warmth, overreactivity and psychological control at Time 3. Mediation analysis revealed both direct and indirect effects. No differences in associations were found for perceived parenting of mothers and fathers. This study demonstrates that child personality in late childhood is significantly related to perceived parental warmth, overreactivity and psychological control in adolescence. In addition, parental sense of competence mediates the relationship between child conscientiousness and perceived parental warmth, overreactivity and psychological control.     

A unique look at face processing: the impact of masked faces on the processing of facial features

This experiment utilized a masked priming paradigm to explore the early processes involved in face recognition. The first experiment investigated implicit processing of the eyes and mouth in an upright face, using prime durations of 33 and 50 ms. The results demonstrate implicit processing of both the eyes and mouth, and support the configural processing theory of face processing. The second experiment used the same method with inverted faces and the third experiment was a combination of Experiments 1 and 2. The fourth experiment utilized misaligned faces as the primes. Based on the pattern of results from these experiments, we suggest that, when a face is inverted, the eyes and mouth are initially processed individually and are not linked until a later stage of processing. An upright face is proposed to be processed by analysis of its configuration, whereas an inverted face is initially processed using first-order relational information, and then converted to an upright representation and transferred to face specific regions for configural analysis.     

Cultural Predictors of Physical and Mental Health Status among Mexican American Women: A Mediation Model

This study, using secondary data analysis, examined a mediation model of acculturation and ethnic pride as predictors of physical and mental health outcomes in a sample of 561 Mexican American women. Factors postulated as mediators were family support and religiosity. Systematic across-group comparison analyses were conducted to examine sources of differences in the mediation model between immigrant and non-immigrant women. The results partially supported the hypothesized mediation model, indicating that family support, but not religiosity, was a significant mediator in the relationship between ethnic pride and mental health problems. In addition, as differences between immigrant and non-immigrant women were observed only in the variables means, but not in the factor loadings or regression paths, the model tested may capture a common psychosocial process that affects these women and their health outcomes. Overall, this study offers important implications for future research and the design of intervention programs for Mexican American women.     

Discrimination of faces and houses by rhesus monkeys: the role of stimulus expertise and rotation angle

The face inversion effect, or impaired recognition of upside down compared to upright faces, is used as a marker for the configural processing of faces in primates. The inversion effect in humans and chimpanzees is strongest for categories of stimuli for which subjects have considerable expertise, primarily conspecifics’ faces. Moreover, discrimination performance decreases linearly as faces are incrementally rotated from upright to inverted. This suggests that rotated faces must be transformed, or normalized back into their most typical viewpoint before configural processing can ensue, and the greater the required normalization, the greater the likelihood of errors resulting. Previous studies in our lab have demonstrated a general face inversion effect in rhesus monkeys that was not influenced by expertise. Therefore, the present study examined the influence of rotation angle on the visual perception of face and nonface stimuli that varied in their level of expertise to further delineate the processes underlying the inversion effect in rhesus monkeys. Five subjects discriminated images in five orientation angles. Results showed significant linear impairments for all stimulus categories, including houses. However, compared to the upright images, only rhesus faces resulted in worse performance at rotation angles greater than 45°, suggesting stronger configural processing for stimuli for which subjects had the greatest expertise.     

Configural instability of data from the Life Orientation Test—Revised

Scores obtained with the Revised Life Orientation Test (LOT-R) are commonly interpreted according to the optimism–pessimism factorial model. Positive items would measure individual differences in positive outcome expectancy, and negative items would measure differences in negative outcome expectancy. Configural stability was assessed using four datasets from French adults, N₁ = 429, N₂ = 278, N₃ = 468, and N₄ = 909. Two times out of four the third positive item-variable could also be regressed on the pessimism factor, with a significant improvement of the goodness of fit. Moreover, the semantic content of the best items reveals that the positive vs. negative outcome expectancy interpretation of the factors was not self-consistent. Practical consequences for the use of the usual optimism composite score are discussed.     

Proactive personality and career adaptability: The role of thriving at work

This is a pioneer study to examine the mechanism underlying the relationship between proactive personality and career adaptability. Using a moderated mediation approach, it tested the mediating effect of thriving on this relationship and the moderating effect of proactive personality on the relationship between thriving and career adaptability. Three hundred and sixty-four adult employees participated in the survey study. Results demonstrated that proactive personality first promoted individuals' thriving at work, which in turn led to improved career adaptability. In addition, the effect of thriving on career adaptability was found to be stronger for those individuals with low rather than high proactive personality. In supporting this, the moderated mediation analysis further indicated that low proactive individuals, compared to their high proactive counterparts, relied more on thriving when developing career adaptability resources. These findings have important implications for career research and career counseling practices.     

Individual Accountability in Cooperative Learning Groups at the College Level: Differential Effects on High,Average, and Low Exam Performers

Over a three-semester period in a large undergraduate human development course, students were assigned to 5–7 member groups to work together in preparing for an exam in one of the five content units in the course. Their exam performance was tracked over three units: a baseline unit in which students worked only individually, a unit in which they worked in cooperative teams, and a follow-up unit in which the formal cooperative team structure was removed. Three different bonus-credit contingencies were used in the cooperative learning unit across the three semesters: (a) awarding full bonus credit to each individual in the group if the group as a whole improved its exam performance by the specified amount, (b) awarding partial bonus credit to each individual in the group if the group as a whole improved it exam performance by the specified amount and full bonus credit to each individual who also improved by the specified amount, and (c) awarding full bonus credit to an individual in the group if both the group and the individual improved exam performance by the specified amount. The three contingencies produced somewhat similar patterns of change for low and average performers, but the high performers fared better under the last two contingencies than under the group-only contingency.