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).     

Contrastive Constraints Guide Explanation‐Based Category Learning

This paper provides evidence for a contrastive account of explanation that is motivated by pragmatic theories that recognize the contribution that context makes to the interpretation of a prompt for explanation. This study replicates the primary findings of previous work in explanation‐based category learning (Williams & Lombrozo, 2010), extending that work by illustrating the critical role of the context in this type of learning. Participants interacted with items from two categories either by describing the items or explaining their category membership. We manipulated the feature overlap between the categories and examined both the explanations generated and acquired knowledge of the categories. Explanations for membership in a given category were influenced by the unprompted contrast category, indicating an important role for contrastive processing in the generation of explanations. The influence of the contrast category was similarly seen in the transfer performance of the participants.     

No blank slates: Pre-existing schemas about pharmaceuticals predict memory for side effects

Objectives: Attribution of symptoms as medication side effects is informed by pre-existing beliefs about medicines and perceptions of personal sensitivity to their effects (pharmaceutical schemas). We tested whether (1) pharmaceutical schemas were associated with memory (recall/recognition) for side effect information (2) memory explained the attribution of a common unrelated symptom as a side effect.

Design: In this analogue study participants saw the patient leaflet of a fictitious asthma drug listing eight side effects.

Main outcome measures: We measured recall and recognition memory for side effects and used a vignette to test whether participants attributed an unlisted common symptom (headache) as a side effect.

Results: Participants who perceived pharmaceuticals as more harmful in general recalled fewer side effects correctly (r_{Correct Recall} = ?.273), were less able to differentiate between listed and unlisted side effects (r_{Recognition Sensitivity} = ?.256) and were more likely to attribute the unlisted headache symptom as a side effect (r_{side effect attribution} = .381, ps < .01). The effect of harm beliefs on side effect attribution was partially mediated by correct recall of side effects.

Conclusion: Pharmaceutical schemas are associated with memory for side effect information. Memory may explain part of the association between pharmaceutical schemas and the attribution of unrelated symptoms as side effects.     

Die‐by Framing both Lengthens and Shortens Life: Further Evidence on Constructed Beliefs in Life Expectancy

Decisions regarding consumption over the lifespan require some estimate of how long that lifespan is likely to be. Payne et al. (2013) found that respondents' estimates of their own life expectancy are on average 8.6 years shorter when elicited using a die‐by frame than when elicited by a live‐to frame. If decision makers act on these life expectancies, then an arbitrary detail of framing will lead to drastically different choices. We propose that the framing effect is sensitive to the iterative probabilistic elicitation procedure employed by the previous literature. Study 1 compares the framing effect across the iterative probabilistic procedure and a point estimate procedure that simply asks respondents the age they will live to/die by. The iterative probabilistic procedure implies a life expectancy six years shorter in the die‐by frame than in the live‐to frame, replicating the results of Payne et al. (2013). With the point estimate procedure, however, the framing effect reverses: the die‐by frame increases life expectancy by three years. In Study 2, we test for the framing effect using a point estimate procedure on a representative sample of 2000 Britons. Again, and in contrast with the previous literature, we find that the die‐by frame implies longer life. Our results reinforce the previous literature that beliefs around life expectancy are constructed. We recommend caution when attempting to debias life expectancy estimates or using life expectancies in choice architecture. Copyright © 2017 John Wiley & Sons, Ltd.     

Categories of Large Numbers in Line Estimation

How do people stretch their understanding of magnitude from the experiential range to the very large quantities and ranges important in science, geopolitics, and mathematics? This paper empirically evaluates how and whether people make use of numerical categories when estimating relative magnitudes of numbers across many orders of magnitude. We hypothesize that people use scale words—thousand, million, billion—to carve the large number line into categories, stretching linear responses across items within each category. If so, discontinuities in position and response time are expected near the boundaries between categories. In contrast to previous work (Landy, Silbert, & Goldin, 2013) that suggested only that a minority of college undergraduates employed categorical boundaries, we find that discontinuities near category boundaries occur in most or all participants, but that accurate and inaccurate participants respond in opposite ways to category boundaries. Accurate participants highlight contrasts within a category, whereas inaccurate participants adjust their responses toward category centers.     

Dealing with Big Numbers: Representation and Understanding of Magnitudes Outside of Human Experience

Being able to estimate quantity is important in everyday life and for success in the STEM disciplines. However, people have difficulty reasoning about magnitudes outside of human perception (e.g., nanoseconds, geologic time). This study examines patterns of estimation errors across temporal and spatial magnitudes at large scales. We evaluated the effectiveness of hierarchical alignment in improving estimations, and transfer across dimensions. The activity was successful in increasing accuracy for temporal and spatial magnitudes, and learning transferred to the estimation of numeric magnitudes associated with events and objects. However, there were also a number of informative differences in performance on temporal, spatial, and numeric magnitude measures, suggesting that participants possess different categorical information for these scales. Educational implications are discussed.     

道德概念净脏隐喻及其对道德判断的影响

通过3个实验考察道德概念净脏隐喻的心理现实性以及道德概念净脏背景和净脏自身隐喻对道德判断的影响及其差异。结果表明：（1）道德概念净脏隐喻具有心理现实性,即被试在洁净背景上判断道德词的反应时更快,在肮脏背景上判断不道德词的反应时更快。（2）当将道德两难故事呈现在肮脏背景上时,相比于呈现在洁净背景上,被试更容易将故事主人公的行为判断为不道德,表现出隐喻一致性效应。（3）相比于肮脏自身启动,被试在洁净自身启动下对道德两难故事主人公的行为判断为更加不道德,表现出隐喻补偿性效应。（4）相比于洁净背景启动,被试在洁净自身启动下对道德两难故事的判断更加严厉;相比于肮脏背景启动,被试在肮脏自身启动下对道德两难故事的判断更加宽松。研究结果证明,道德概念净脏隐喻具有心理现实性,净脏背景和净脏自身隐喻均影响个体的道德判断,并且二者对道德判断的影响不同。     

Values, Framing, and Citizens' Thoughts about Policy Issues: Effects on Content and Quantity

This study examines how frames invoking a core value shape the content and quantity of citizens' thoughts about a policy issue. An experimental study showed that exposure to a pro-school voucher equality frame increased the probability that participants would invoke equality in their open-ended survey responses. Exposure to an anti-school voucher equality frame produced the same effect, as did exposure to both frames. At the same time, participants who received either frame or both frames provided fewer open-ended responses. Thus, the frames appeared to focus participants' thoughts on one value while reducing the overall extent to which they thought about the issue. In broader terms, value framing may have implications for the nature and quality of public deliberation about policy issues—a point that scholars should keep in mind when considering how to define and study framing effects.     

When Is More Better?

Abstract— We examine three determinants of the relationship between the magnitude of a stimulus and a person's subjective "value" of that stimulus: the process by which value is assessed (either by feeling or by calculation), the evaluability of the relevant magnitude variable (whether the desirability of a given level of that variable can be evaluated independently), and the mode of evaluation (whether stimuli are encountered and evaluated jointly or separately). Reliance on feeling, lack of evaluability, and separate evaluation lead to insensitivity to magnitude. An analysis invoking these factors provides a novel account for why people typically become less sensitive to changes in the magnitude of a stimulus as magnitude increases.     

儿童类别学习中知识效应的年龄差异

采用特征主题的类别学习实验范式,考察了儿童类别学习中知识效应的年龄差异。63名小学4年级学生(年龄范围9～10岁)、65名小学6年级学生(年龄范围11～12岁)和77名初中2年级学生(年龄范围13～14岁)参加了本实验。结果表明:当类别特征能够在已有知识的基础上形成主题时,3个年龄组儿童类别学习的轮次和错误数均显著下降,而且主题突出时,这种趋势更加明显;在统一主题条件下,小学4年级、小学6年级和初中2年级3个年龄组儿童类别学习的轮次和错误数依次减少;而在无主题和突出主题条件下,3个年龄组儿童类别学习的成绩无显著差异。