Statistical approaches for enhancing causal interpretation of the M to Y relation in mediation analysis.

Statistical mediation methods provide valuable information about underlying mediating psychological processes, but the ability to infer that the mediator variable causes the outcome variable is more complex than widely known. Researchers have recently emphasized how violating assumptions about confounder bias severely limits causal inference of the mediator to dependent variable relation. Our article describes and addresses these limitations by drawing on new statistical developments in causal mediation analysis. We first review the assumptions underlying causal inference and discuss three ways to examine the effects of confounder bias when assumptions are violated. We then describe four approaches to address the influence of confounding variables and enhance causal inference, including comprehensive structural equation models, instrumental variable methods, principal stratification, and inverse probability weighting. Our goal is to further the adoption of statistical methods to enhance causal inference in mediation studies.

Mechanisms of motivational interviewing in health promotion: a Bayesian mediation analysis.

BACKGROUND: Counselor behaviors that mediate the efficacy of motivational interviewing (MI) are not well understood, especially when applied to health behavior promotion. We hypothesized that client change talk mediates the relationship between counselor variables and subsequent client behavior change. METHODS: Purposeful sampling identified individuals from a prospective randomized worksite trial using an MI intervention to promote firefighters' healthy diet and regular exercise that increased dietary intake of fruits and vegetables (n = 21) or did not increase intake of fruits and vegetables (n = 22). MI interactions were coded using the Motivational Interviewing Skill Code (MISC 2.1) to categorize counselor and firefighter verbal utterances. Both Bayesian and frequentist mediation analyses were used to investigate whether client change talk mediated the relationship between counselor skills and behavior change. RESULTS: Counselors' global spirit, empathy, and direction and MI-consistent behavioral counts (e.g., reflections, open questions, affirmations, emphasize control) significantly correlated with firefighters' total client change talk utterances (rs = 0.42, 0.40, 0.30, and 0.61, respectively), which correlated significantly with their fruit and vegetable intake increase (r = 0.33). Both Bayesian and frequentist mediation analyses demonstrated that findings were consistent with hypotheses, such that total client change talk mediated the relationship between counselor's skills--MI-consistent behaviors [Bayesian mediated effect: αß = .06 (.03), 95% CI = .02, .12] and MI spirit [Bayesian mediated effect: αß = .06 (.03), 95% CI = .01, .13]--and increased fruit and vegetable consumption. CONCLUSION: Motivational interviewing is a resource- and time-intensive intervention, and is currently being applied in many arenas. Previous research has identified the importance of counselor behaviors and client change talk in the treatment of substance use disorders. Our results indicate that similar mechanisms may underlie the effects of MI for dietary change. These results inform MI training and application by identifying those processes critical for MI success in health promotion domains.

Prejudices and discrimination as goal activated and threat driven: The affordance management approach applied to sexual prejudice.

Stereotypes, prejudices, and discriminatory behaviors directed toward people based on their sexual orientation vary broadly. Existing perspectives on sexual prejudice argue for different underlying causes, sometimes provide disparate or conflicting evidence for its roots, and typically fail to account for variances observed across studies. We propose an affordance management approach to understanding sexual prejudice, which weds the fundamental motives theory with the sociofunctional threat-based approach to prejudice to provide a broader explanation for the causes and outcomes of sexual prejudice and to explain inter- and intragroup prejudices more broadly. Prejudices arise as specific emotions designed to engage functional behavioral responses to perceived threats and opportunities (i.e., affordances) posed by different sexual orientation groups, and interact with the perceiver's chronic or temporarily activated fundamental motives (e.g., parenting, mating), which determine the relevance of certain target affordances. Our perspective predicts what stereotype content is likely to direct specific affective and behavioral reactions (i.e., the stereotypes that relay threat- and opportunity-relevant information) and when the affordance-emotion-behavior link is likely to engage (i.e., when those threats and opportunities are directly relevant to the perceiver's current fundamental goal). This article synthesizes the extant sexual prejudice literature from an affordance management approach to demonstrate how fundamental goals interact with preexisting perceptions to drive perceptual, affective, and behavioral responses toward sexual orientation groups, and provides a degree of explanatory power heretofore missing from the prejudice literature. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Design approaches to experimental mediation.

Identifying causal mechanisms has become a cornerstone of experimental social psychology, and editors in top social psychology journals champion the use of mediation methods, particularly innovative ones when possible (e.g. Halberstadt, 2010, Smith, 2012). Commonly, studies in experimental social psychology randomly assign participants to levels of the independent variable and measure the mediating and dependent variables, and the mediator is assumed to causally affect the dependent variable. However, participants are not randomly assigned to levels of the mediating variable(s), i.e., the relationship between the mediating and dependent variables is correlational. Although researchers likely know that correlational studies pose a risk of confounding, this problem seems forgotten when thinking about experimental designs randomly assigning participants to levels of the independent variable and measuring the mediator (i.e., "measurement-of-mediation" designs). Experimentally manipulating the mediator provides an approach to solving these problems, yet these methods contain their own set of challenges (e.g., Bullock, Green, & Ha, 2010). We describe types of experimental manipulations targeting the mediator (manipulations demonstrating a causal effect of the mediator on the dependent variable and manipulations targeting the strength of the causal effect of the mediator) and types of experimental designs (double randomization, concurrent double randomization, and parallel), provide published examples of the designs, and discuss the strengths and challenges of each design. Therefore, the goals of this paper include providing a practical guide to manipulation-of-mediator designs in light of their challenges and encouraging researchers to use more rigorous approaches to mediation because manipulation-of-mediator designs strengthen the ability to infer causality of the mediating variable on the dependent variable.

Perceptions of Threats to Physical Safety, Sexual Autonomy, Values, and of Discrimination Drive LGB Prejudices Toward Heterosexuals.

Many studies have investigated heterosexuals' prejudices toward nonheterosexuals, yet LGB's prejudices toward heterosexuals remain largely unexplored. Therefore, we sought to determine the threats and opportunities (i.e., affordances) LGB perceive heterosexuals to pose and whether those affordances explain their sexual prejudices toward heterosexuals. Study 1 analyzed LGB's reasons for liking and disliking heterosexuals, which determined whether the threats predicted to be salient for LGB mirrored the affordances they generated. Study 2 measured these perceived affordances and examined the extent to which they drove LGB's prejudices toward heterosexuals. Generally, perceptions of discrimination and unreciprocated sexual interest threats drove anger, physical safety and sexual autonomy threats drove fear, and values threats drove moral disgust toward heterosexuals, although results varied slightly by perceiver and target groups. Goals to alleviate the tensions between heterosexuals and LGB require an understanding of the dynamics between these groups. This research provides preliminary insights into understanding those dynamics.