Behavioural science is unlikely to change the world without a heterogeneity revolution

Continuous and discrete proportion elicit different cognitive strategies

Despite proportional information being ubiquitous, there is not a standard account of proportional reasoning. Part of the difficulty is that there are several apparent contradictions: in some contexts, proportion is easy and privileged, while in others it is difficult and ignored. One possibility is that although we see similarities across tasks requiring proportional reasoning, people approach them with different strategies. We test this hypothesis by implementing strategies computationally and quantitatively comparing them with Bayesian tools, using data from continuous (e.g., pie chart) and discrete (e.g., dots) stimuli and preschoolers, 2nd and 5th graders, and adults. Overall, people's comparisons of highly regular and continuous proportion are better fit by proportion strategy models, but comparisons of discrete proportion are better fit by a numerator comparison model. These systematic differences in strategies suggest that there is not a single, simple explanation for behavior in terms of success or failure, but rather a variety of possible strategies that may be chosen in different contexts.

We meat again: a field study on the moderating role of location-specific consumer preferences in nudging vegetarian options

This field study set out to test whether consumers' history of making decisions in a particular choice context moderated the effectiveness of a nudge intervention to reduce meat consumption. In a Danish hospital canteen that served both staff members and visitors, a combination of nudges (Chef's recommendation sticker + prominent positioning) was implemented to promote vegetarian sandwiches. The sales of these sandwiches increased from 16.45% during the baseline period to 25.16% during the nudge intervention period. Most notably, this increase was caused by the visitors, who had weak location-bound preferences. Hospital staff members (who had strong location-bound preferences) were unaffected by the nudge in their choice. This is an important finding because the two consumer groups did not differ on their person-bound preferences for meat. It seems that behaviour change is best predicted by location-bound preferences, whereas the behaviour itself is best predicted by person-bound preferences. These findings can help organizations in estimating whether a nudge intervention has enough potential for behaviour change, or whether more directive policies are required.

A bird's-eye view of research practices in mathematical cognition, learning, and instruction: Reimagining the status quo

Research on mathematical cognition, learning, and instruction (MCLI) often takes cognition as its point of departure and considers instruction at a later point in the research cycle. In this article, we call for psychologists who study MCLI to reflect on the "status quo" of their research practices and to consider making instruction an earlier and more central aspect of their work. We encourage scholars of MCLI (a) to consider the needs of educators and schools when selecting research questions and developing interventions; (b) to compose research teams that are diverse in the personal, disciplinary, and occupational backgrounds of team members; (c) to make efforts to broaden participation in research and to conduct research in authentic settings; and (d) to communicate research in ways that are accessible to practitioners and to the general public. We argue that a more central consideration of instruction will lead to shifts that make research on MCLI more theoretically valuable, more actionable for educators, and more relevant to pressing societal challenges.

Human detection of political speech deepfakes across transcripts, audio, and video

Recent advances in technology for hyper-realistic visual and audio effects provoke the concern that deepfake videos of political speeches will soon be indistinguishable from authentic video. We conduct 5 pre-registered randomized experiments with N = 2215 participants to evaluate how accurately humans distinguish real political speeches from fabrications across base rates of misinformation, audio sources, question framings with and without priming, and media modalities. We do not find base rates of misinformation have statistically significant effects on discernment. We find deepfakes with audio produced by the state-of-the-art text-to-speech algorithms are harder to discern than the same deepfakes with voice actor audio. Moreover across all experiments and question framings, we find audio and visual information enables more accurate discernment than text alone: human discernment relies more on how something is said, the audio-visual cues, than what is said, the speech content.

What Is Behavioral Complexity? Lay Perceptions of Characteristics of Complex Behavior

A behavior's complexity may impact habit formation, with implications for habit-based public health and environmental intervention designs. However, there are varying conceptualizations of behavioral complexity, hindering the synthesis of findings. To develop a unified definition, the aim of this study was to explore perceptions of behavioral complexity and identify behaviors that exemplify aspects of complexity. Participants (N = 225) completed a questionnaire concerning the complexity of various health and environmental behaviors, the importance of complexity characteristics previously identified by researchers (novelty, difficulty, steps, planning, immediacy of reward, time, attention, skill, mental resources, self-efficacy, motivation for a behavior, and supportiveness of the context) and demographics. Participants considered all proposed characteristics to be important. Complex behaviors (e.g., abstaining from smoking and taking insulin shots), compared to simple behaviors (e.g., eating fruit and stretching), are more likely to be true to the previously identified characteristics. Perceived complexity is influenced by several salient characteristics. Results may contribute to a synthesized definition and underpin future research to better identify behavior change techniques to foster habitual behaviors of varying complexity. Hence, researchers, practitioners, and policymakers may identify common barriers and facilitators of behavior to target in interventions. However, further research is required to contextualize the findings.

Heterogeneity in effect size estimates

A typical empirical study involves choosing a sample, a research design, and an analysis path. Variation in such choices across studies leads to heterogeneity in results that introduce an additional layer of uncertainty, limiting the generalizability of published scientific findings. We provide a framework for studying heterogeneity in the social sciences and divide heterogeneity into population, design, and analytical heterogeneity. Our framework suggests that after accounting for heterogeneity, the probability that the tested hypothesis is true for the average population, design, and analysis path can be much lower than implied by nominal error rates of statistically significant individual studies. We estimate each type's heterogeneity from 70 multilab replication studies, 11 prospective meta-analyses of studies employing different experimental designs, and 5 multianalyst studies. In our data, population heterogeneity tends to be relatively small, whereas design and analytical heterogeneity are large. Our results should, however, be interpreted cautiously due to the limited number of studies and the large uncertainty in the heterogeneity estimates. We discuss several ways to parse and account for heterogeneity in the context of different methodologies.

Causal inference on human behaviour

Making causal inferences regarding human behaviour is difficult given the complex interplay between countless contributors to behaviour, including factors in the external world and our internal states. We provide a non-technical conceptual overview of challenges and opportunities for causal inference on human behaviour. The challenges include our ambiguous causal language and thinking, statistical under- or over-control, effect heterogeneity, interference, timescales of effects and complex treatments. We explain how methods optimized for addressing one of these challenges frequently exacerbate other problems. We thus argue that clearly specified research questions are key to improving causal inference from data. We suggest a triangulation approach that compares causal estimates from (quasi-)experimental research with causal estimates generated from observational data and theoretical assumptions. This approach allows a systematic investigation of theoretical and methodological factors that might lead estimates to converge or diverge across studies.

What ergodicity means for you

This paper explores the relation between within-person and between-person research designs using the concept of ergodicity from statistical mechanics in physics. We demonstrate the consequences of ergodicity using several real data examples from previously published studies. We then create several simulated examples that illustrate the independence of within-person processes from between-person differences, and pair these examples with analytic results that reinforce our conclusions. Finally, we discuss the plausibility of ergodicity being the general rule rather than the exception for social and behavioral processes, address common arguments against heeding the implications of ergodicity for behavioral research, and offer several possible solutions.

The effectiveness of interventions to prevent and reduce child maltreatment in high-income countries: An umbrella review

BACKGROUND

In recent decades, many interventions targeting the occurrence (primary prevention) or the recurrence (secondary prevention) of child abuse and neglect have been tested. Findings have been synthesized in several meta-analyses and systematic reviews. However, the range of interventions addressed in these studies is very broad, and an integrative assessment of this large spectrum is lacking.

OBJECTIVE

Focusing on high-income countries, we ask (i) what is known about the effectiveness of interventions to prevent or reduce child abuse and neglect and (ii) how robust this evidence is.

METHODS

A systematic review of systematic reviews, called an umbrella review, was conducted. Ten databases on OvidSP and Web of Science were searched up until April 2023. Narrative synthesis was used to document the publications' findings.

RESULTS

44 publications were included in the umbrella review. We did not find that any type of intervention had a clear, consistent, and robust track record of preventing or reducing the occurrence of child abuse and neglect. Rather, publications examining the effectiveness of interventions in all areas frequently reported non-existent, small or inconsistent effects. However, positive effects for particular interventions in specific settings did emerge. Research methodologies showed several and often severe problems.

CONCLUSIONS

We suggest several measures to improve the quality of research and call on practitioners to be persistent in developing more effective interventions.

Examining the effects of increasing then decreasing exercise intensity within a session of aerobic exercise

Recent studies have examined the relations between the slope of pleasure experienced during exercise and remembered pleasure, forecasted pleasure, and enjoyment.

OBJECTIVES

This study advances this line of research by examining the effects of exposing participants to exercise that increases in intensity and then decreases in intensity.

METHODS

In a within-subjects design, participants completed three exercise sessions matched for total and average work. One session steadily increased in intensity, another steadily decreased in intensity, and a third increased-then-decreased in intensity. Remembered pleasure, forecasted pleasure, and exercise enjoyment served as primary outcome variables.

RESULTS

Remembered pleasure, forecasted pleasure, and enjoyment did not differ between conditions. Remembered pleasure was positively associated with mean experienced pleasure, the overall slope of pleasure during the exercise session, affect experienced at the end of exercise, forecasted pleasure, accomplishment, and enjoyment.

CONCLUSIONS

These data add to a growing literature on the effects of patterns of exercise intensity on affective responses to exercise. The results are discussed in context of previous and more recent research.

The amygdala volume moderates the relationship between childhood maltreatment and callous-unemotional traits in adolescents with conduct disorder

CU traits, characterized by shallow affect, lack of fear, and absence of remorse, have been moderately associated with childhood maltreatment in a recent meta-analysis. However, the potential impact of brain structures remains undetermined. This paper examines the relationship between callous-unemotional (CU) traits, childhood maltreatment, and amygdala volumes. In this study, we used a region-of-interest (ROI) analysis to explore the interaction between the volumes of the amygdala, childhood maltreatment, and the manifestation of CU traits in adolescents diagnosed with conduct disorder (CD, N = 67), along with a comparison group of healthy-control youths (HCs, N = 89). The ROI analysis revealed no significant group differences in the bilateral amygdalar volumes. Significant positive correlation was discovered between all forms of child maltreatment (except for physical neglect) and CU traits across subjects. But the interaction of physical abuse and amygdala volumes was only significant within CD patients. Notably, a sensitivity analysis suggested that gender significantly influences these findings. These results contribute critical insights into the etiology of CU traits, emphasizing the need for customized clinical assessment tools and intervention strategies.

Examining Dyadic Stress Appraisal Processes Within Romantic Relationships from a Challenge and Threat Perspective

The biopsychosocial model of challenge and threat emphasizes how individuals appraise stress. Close relationship theories emphasize the interpersonal context, communication, and outcomes that arise from stress. We integrate these approaches by examining the individual variability surrounding appraisals of sufficient (more challenge, less threat) or insufficient (more threat, less challenge) resources to cope with demands and examining how these appraisals are associated with couples' behavior and feelings toward each other. Across three studies, 459 romantic couples (N = 918), and various potentially stressful in-lab conversations (extra-dyadic problem, dislikes about each other, dependability, and relationship conflict), we found evidence that stress appraisals indicative of more challenge and less threat were associated with more approach- and less avoidance-oriented behaviors within interactions. These approach- and avoidance-oriented behaviors were associated with greater feelings of relationship security and well-being after the conversation. However, whose (actors or partners) appraisals and behaviors were associated with security and well-being varied across the three studies. This work provides theoretical and empirical evidence for an interpersonal emphasis on intraindividual stress appraisal processes through a dyadic and close relationships lens. Our integrative theoretical framework breaks away from the idea that stress is inherently "bad" or "maladaptive" to show that appraising stress as more manageable (more challenge, less threat) is associated with more relationship behaviors that approach incentives and less that avoid threats and enhance feelings of relationship security and well-being.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42761-024-00235-3.

Disorder-specific versus transdiagnostic cognitive mechanisms in anxiety and depression: Machine-learning-based prediction of symptom severity

INTRODUCTION

Psychiatric evaluation of anxiety and depression is currently based on self-reported symptoms and their classification into discrete disorders. Yet the substantial overlap between these disorders as well as their within-disorder heterogeneity may contribute to the mediocre success rates of treatments. The proposed research examines a new framework for diagnosis that is based on alterations in underlying cognitive mechanisms. In line with the Research Domain Criteria (RDoC) approach, the current study directly compares disorder-specific and transdiagnostic cognitive patterns in predicting the severity of anxiety and depression symptoms.

METHODS

The sample included 237 individuals exhibiting differing levels of anxiety and depression symptoms, as measured by the STAI-T and BDI-II. Random Forest regressors were used to analyze their performance on a battery of six computerized cognitive-behavioral tests targeting selective and spatial attention, expectancy, interpretation, memory, and cognitive control biases.

RESULTS

Unique anxiety-specific biases were found, as well as shared anxious-depressed bias patterns. These cognitive biases exhibited relatively high fitting rates when predicting symptom severity (questionnaire scores common range 0-60, MAE = 6.03, RMSE = 7.53). Interpretation and expectancy biases exhibited the highest association with symptoms, above all other individual biases.

LIMITATIONS

Although internal validation methods were applied, models may suffer from potential overfitting due to sample size limitations.

CONCLUSION

In the context of the ongoing dispute regarding symptom-centered versus transdiagnostic approaches, the current study provides a unique comparison of these two views, yielding a novel intermediate approach. The results support the use of mechanism-based dimensional diagnosis for adding precision and objectivity to future psychiatric evaluations.

A behaviour and disease transmission model: incorporating the Health Belief Model for human behaviour into a simple transmission model

The health and economic impacts of infectious diseases such as COVID-19 affect all levels of a community from the individual to the governing bodies. However, the spread of an infectious disease is intricately linked to the behaviour of the people within a community since crowd behaviour affects individual human behaviour, while human behaviour affects infection spread, and infection spread affects human behaviour. Capturing these feedback loops of behaviour and infection is a well-known challenge in infectious disease modelling. Here, we investigate the interface of behavioural science theory and infectious disease modelling to explore behaviour and disease (BaD) transmission models. Specifically, we incorporate a visible protective behaviour into the susceptible-infectious-recovered-susceptible (SIRS) transmission model using the socio-psychological Health Belief Model to motivate behavioural uptake and abandonment. We characterize the mathematical thresholds for BaD emergence in the BaD SIRS model and the feasible steady states. We also explore, under different infectious disease scenarios, the effects of a fully protective behaviour on long-term disease prevalence in a community, and describe how BaD modelling can investigate non-pharmaceutical interventions that target-specific components of the Health Belief Model. This transdisciplinary BaD modelling approach may reduce the health and economic impacts of future epidemics.

Field testing the transferability of behavioural science knowledge on promoting vaccinations

As behavioural science is increasingly adopted by organizations, there is a growing need to assess the robustness and transferability of empirical findings. Here, we investigate the transferability of insights from various sources of behavioural science knowledge to field settings. Across three pre-registered randomized controlled trials (RCTs, N = 314,824) involving a critical policy domain-COVID-19 booster uptake-we field tested text-based interventions that either increased vaccinations in prior field work (RCT1, NCT05586204), elevated vaccination intentions in an online study (RCT2, NCT05586178) or were favoured by scientists and non-experts (RCT3, NCT05586165). Despite repeated exposure to COVID-19 vaccination messaging in our population, reminders and psychological ownership language increased booster uptake, replicating prior findings. However, strategies deemed effective by prediction or intention surveys, such as encouraging the bundling of COVID-19 boosters and flu shots or addressing misconceptions, yielded no detectable benefits over simple reminders. These findings underscore the importance of testing interventions' transferability to real-world settings.

Better, for worse, or both? Testing environmental sensitivity models with parenting at the level of individual families

According to environmental sensitivity models, children vary in responsivity to parenting. However, different models propose different patterns, with responsivity to primarily: (1) adverse parenting (adverse sensitive); or (2) supportive parenting (vantage sensitive); or (3) to both (differentially susceptible). This preregistered study tested whether these three responsivity patterns coexist. We used intensive longitudinal data of Dutch adolescents (N = 256, Mage = 14.8, 72% female) who bi-weekly reported on adverse and supportive parenting and their psychological functioning (tmean = 17.7, tmax = 26). Dynamic Structural Equation Models (DSEM) indeed revealed differential parenting effects. As hypothesized, we found that all three responsivity patterns coexisted in our sample: 5% were adverse sensitive, 3% vantage sensitive, and 26% differentially susceptible. No adolescent appeared unsusceptible, however. Instead, we labeled 28% as unperceptive, because they did not perceive any changes in parenting and scored lower on trait environmental sensitivity than others. Furthermore, unexpected patterns emerged, with 37% responding contrary to parenting theories (e.g., decreased psychological functioning after more parental support). Sensitivity analyses with concurrent effects and parent-reported parenting were performed. Overall, findings indicate that theorized responsivity-to-parenting patterns might coexist in the population, and that there are other, previously undetected patterns that go beyond environmental sensitivity models.

What Environments Support Reading Growth Among Current Compared With Former Reading Intervention Recipients? A Multilevel Analysis of Students and Their Schools

School context can shape relative intervention response in myriad ways due to factors, such as instructional quality, resource allocation, peer effects, and correlations between the school context and characteristics of enrolled students (e.g., higher-poverty students attending higher-poverty schools). In the current study, we used data from 16,000 Grade 3 students in a community-based supplemental reading intervention program to investigate the degree to which school context factors (percentage eligible for free/reduced-price lunch [FRPL], school-level achievement) relate to the differences in triannual reading fluency growth rates between students actively receiving supplemental intervention (active recipients) and those that formerly received intervention (and therefore only received general class instruction at this time; former recipients). Using Bayesian multilevel modeling, our findings indicate that school-level FRPL eligibility played a more prominent factor in growth rate differences between these two groups than school-level reading achievement. However, school-level reading achievement was much more strongly related to reading fluency differences between active and former intervention recipients at the beginning of the school year (when controlling for FRPL). Implications for investigating school-level heterogeneity in intervention response and sustainability are discussed.

Do dyadic interventions impact biomarkers of child health? A state-of-the-science narrative review

BACKGROUND

Early life adversity is related to numerous poor health outcomes in childhood; however, dyadic interventions that promote sensitive and responsive caregiving may protect children from the negative consequences of such exposures. To date, quasi-experimental and randomized controlled trials (RCTs) have examined the impact of dyadic interventions on a range of individual biomarkers in children, which may elucidate the relation between early stress exposure and transdiagnostic risk factors for prospective poor health. However, the content of interventions, analytic strategies, and findings vary widely across studies, obscuring key themes in the science and hindering policy and research efforts.

METHODS

We use a narrative approach to review findings from methodologically rigorous (predominantly RCT) studies of dyadic interventions' impacts on different biomarkers in children, including indicators of the hypothalamic-pituitary-adrenal (HPA) axis, parasympathetic (PNS) and sympathetic nervous systems (SNS), brain development, inflammation, and intracellular DNA processes. We contribute to this important area of inquiry through integrating findings across biological systems and identifying contextual and mechanistic factors to depict the current state of the field.

RESULTS

Evidence suggests dyadic interventions improved PNS functioning and advanced brain maturation. Some studies indicated interventions reduced hair cortisol concentrations, systemic inflammation, and resulted in differences in DNA methylation patterns. Findings did not support main effect-level change in salivary measures of HPA axis activity, SNS activity, or telomere length. Importantly, reviewed studies indicated significant heterogeneity in effects across biological systems, underscoring the importance of contextual factors (e.g., adversity subtype and severity) as potential moderators of effects. Further, findings suggested enhanced parenting behaviors may be a mechanism through which dyadic interventions operate on biomarkers.

CONCLUSIONS

We close with future policy and research directions, emphasizing the promise of biologically-informed dyadic interventions for understanding and ameliorating the effects of early adversity on transdiagnostic biomarkers of health.

Using Adaptive Bandit Experiments to Increase and Investigate Engagement in Mental Health

Digital mental health (DMH) interventions, such as text-message-based lessons and activities, offer immense potential for accessible mental health support. While these interventions can be effective, real-world experimental testing can further enhance their design and impact. Adaptive experimentation, utilizing algorithms like Thompson Sampling for (contextual) multi-armed bandit (MAB) problems, can lead to continuous improvement and personalization. However, it remains unclear when these algorithms can simultaneously increase user experience rewards and facilitate appropriate data collection for social-behavioral scientists to analyze with sufficient statistical confidence. Although a growing body of research addresses the practical and statistical aspects of MAB and other adaptive algorithms, further exploration is needed to assess their impact across diverse real-world contexts. This paper presents a software system developed over two years that allows text-messaging intervention components to be adapted using bandit and other algorithms while collecting data for side-by-side comparison with traditional uniform random non-adaptive experiments. We evaluate the system by deploying a text-message-based DMH intervention to 1100 users, recruited through a large mental health non-profit organization, and share the path forward for deploying this system at scale. This system not only enables applications in mental health but could also serve as a model testbed for adaptive experimentation algorithms in other domains.

Exposing omitted moderators: Explaining why effect sizes differ in the social sciences

Policymakers increasingly rely on behavioral science in response to global challenges, such as climate change or global health crises. But applications of behavioral science face an important problem: Interventions often exert substantially different effects across contexts and individuals. We examine this heterogeneity for different paradigms that underlie many behavioral interventions. We study the paradigms in a series of five preregistered studies across one in-person and 10 online panels, with over 11,000 respondents in total. We find substantial heterogeneity across settings and paradigms, apply techniques for modeling the heterogeneity, and introduce a framework that measures typically omitted moderators. The framework's factors (Fluid Intelligence, Attentiveness, Crystallized Intelligence, and Experience) affect the effectiveness of many text-based interventions, producing different observed effect sizes and explaining variations across samples. Moderators are associated with effect sizes through two paths, with the intensity of the manipulation and with the effect of the manipulation directly. Our results motivate observing these moderators and provide a theoretical and empirical framework for understanding and predicting varying effect sizes in the social sciences.

The impact of mindfulness apps on psychological processes of change: a systematic review

Mindfulness-based interventions (MBIs) have demonstrated therapeutic efficacy for various psychological conditions, and smartphone apps that facilitate mindfulness practice can enhance the reach and impact of MBIs. The goal of this review was to summarize the published evidence on the impact of mindfulness apps on the psychological processes known to mediate transdiagnostic symptom reduction after mindfulness practice. A literature search from January 1, 1993, to August 7, 2023 was conducted on three databases, and 28 randomized controlled trials involving 5963 adults were included. Across these 28 studies, 67 outcome comparisons were made between a mindfulness app group and a control group. Between-group effects tended to favor the mindfulness app group over the control group in three psychological process domains: repetitive negative thinking, attention regulation, and decentering/defusion. Findings were mixed in other domains (i.e., awareness, nonreactivity, non-judgment, positive affect, and acceptance). The range of populations examined, methodological concerns across studies, and problems with sustained app engagement likely contributed to mixed findings. However, effect sizes tended to be moderate to large when effects were found, and gains tended to persist at follow-up assessments two to six months later. More research is needed to better understand the impact of these apps on psychological processes of change. Clinicians interested in integrating apps into care should consider app-related factors beyond evidence of a clinical foundation and use app databases to identify suitable apps for their patients, as highlighted at the end of this review.

ENIGMA's simple seven: Recommendations to enhance the reproducibility of resting-state fMRI in traumatic brain injury

Resting state functional magnetic resonance imaging (rsfMRI) provides researchers and clinicians with a powerful tool to examine functional connectivity across large-scale brain networks, with ever-increasing applications to the study of neurological disorders, such as traumatic brain injury (TBI). While rsfMRI holds unparalleled promise in systems neurosciences, its acquisition and analytical methodology across research groups is variable, resulting in a literature that is challenging to integrate and interpret. The focus of this narrative review is to address the primary methodological issues including investigator decision points in the application of rsfMRI to study the consequences of TBI. As part of the ENIGMA Brain Injury working group, we have collaborated to identify a minimum set of recommendations that are designed to produce results that are reliable, harmonizable, and reproducible for the TBI imaging research community. Part one of this review provides the results of a literature search of current rsfMRI studies of TBI, highlighting key design considerations and data processing pipelines. Part two outlines seven data acquisition, processing, and analysis recommendations with the goal of maximizing study reliability and between-site comparability, while preserving investigator autonomy. Part three summarizes new directions and opportunities for future rsfMRI studies in TBI patients. The goal is to galvanize the TBI community to gain consensus for a set of rigorous and reproducible methods, and to increase analytical transparency and data sharing to address the reproducibility crisis in the field.

Unlocking the Benefits of Gender Diversity: How an Ecological-Belonging Intervention Enhances Performance in Science Classrooms

Gender diversity signals inclusivity, but meta-analyses suggest that it does not boost individual or group performance. This research examined whether a social-psychological intervention can unlock the benefits of gender diversity on college physics students' social and academic outcomes. Analyses of 124 introductory physics classrooms at a large research institution in the eastern United States (N = 3,605) indicated that in classrooms doing "business as usual," cross-gender collaboration was infrequent, there was a substantial gender gap in physics classroom belonging, and classroom gender diversity had no effect on performance. The ecological-belonging intervention aimed to establish classroom norms that adversity in the course is normal and surmountable. In classrooms receiving the intervention, cross-gender interaction increased 51%, the gender gap in belonging was reduced by 47%, and higher classroom diversity was associated with higher course grades and 1-year grade point average for both men and women. Addressing contextual belongingness norms may help to unlock the benefits of diversity.

The next generation of developmental psychopathology research: Including broader perspectives and becoming more precise

The current Special Issue marks a major milestone in the history of developmental psychopathology; as the final issue edited by Cicchetti, we have an opportunity to reflect on the remarkable progress of the discipline across the last four decades, as well as challenges and future directions for the field. With contemporary issues in mind, including rising rates of psychopathology, health disparities, and international conflict, as well as rapid growth and accessibility of digital and mobile technologies, the discipline of developmental psychopathology is poised to advance multidisciplinary, developmentally- and contextually- informed research, and to make substantial progress in supporting the healthy development of individuals around the world. We highlight key future directions and challenges for the next generation of developmental psychopathology research including further investigation of culture at multiple levels of analysis, incorporation of macro-level influences into developmental psychopathology research, methods advances to address heterogeneity in translational research, precision mental health, and the extension of developmental psychopathology research across the lifespan.

Psychological inoculation strategies to fight climate disinformation across 12 countries

Decades after the scientific debate about the anthropogenic causes of climate change was settled, climate disinformation still challenges the scientific evidence in public discourse. Here we present a comprehensive theoretical framework of (anti)science belief formation and updating to account for the psychological factors that influence the acceptance or rejection of scientific messages. We experimentally investigated, across 12 countries (N = 6,816), the effectiveness of six inoculation strategies targeting these factors-scientific consensus, trust in scientists, transparent communication, moralization of climate action, accuracy and positive emotions-to fight real-world disinformation about climate science and mitigation actions. While exposure to disinformation had strong detrimental effects on participants' climate change beliefs (δ = -0.16), affect towards climate mitigation action (δ = -0.33), ability to detect disinformation (δ = -0.14) and pro-environmental behaviour (δ = -0.24), we found almost no evidence for protective effects of the inoculations (all δ < 0.20). We discuss the implications of these findings and propose ways forward to fight climate disinformation.

Optimally generate policy-based evidence before scaling

Social scientists have increasingly turned to the experimental method to understand human behaviour. One critical issue that makes solving social problems difficult is scaling up the idea from a small group to a larger group in more diverse situations. The urgency of scaling policies impacts us every day, whether it is protecting the health and safety of a community or enhancing the opportunities of future generations. Yet, a common result is that, when we scale up ideas, most experience a 'voltage drop'-that is, on scaling, the cost-benefit profile depreciates considerably. Here I argue that, to reduce voltage drops, we must optimally generate policy-based evidence. Optimality requires answering two crucial questions: what information should be generated and in what sequence. The economics underlying the science of scaling provides insights into these questions, which are in some cases at odds with conventional approaches. For example, there are important situations in which I advocate flipping the traditional social science research model to an approach that, from the beginning, produces the type of policy-based evidence that the science of scaling demands. To do so, I propose augmenting efficacy trials by including relevant tests of scale in the original discovery process, which forces the scientist to naturally start with a recognition of the big picture: what information do I need to have scaling confidence?

Who feels like they belong? Personality and belonging in college

Having a secure sense of belonging at school supports students' academic achievement and well-being. However, little research has examined how students' personalities relate to their feelings of school belonging. We address this gap in the literature by leveraging data from a large sample of first-year college students (N = 4,753) from a diverse set of North American colleges and universities (N = 12). We found that both extraversion and agreeableness were positively associated with belonging, while neuroticism was negatively associated with belonging. In an exploratory analysis, we examined differences between large and small schools. Students who were more extraverted, less neurotic, and less open were more likely to attend large schools. Additionally, the association between extraversion and belonging was stronger for students at large schools. These findings advance our understanding of who comes to feel like they belong at college and how school context may influence these relationships. We emphasize the need for continued research on the relationship between personality and belonging. Additionally, we highlight the implications of these results for higher education institutions.

Learning to embrace one's stress: the selective effects of short videos on youth's stress mindsets

BACKGROUND AND OBJECTIVES

Stress is not inherently negative. As youth will inevitably experience stress when facing the various challenges of adolescence, they can benefit from developing a stress-can-be-enhancing mindset rather than learning to fear their stress responses and avoid taking on challenges. We aimed to verify whether a rapid intervention improved stress mindsets and diminished perceived stress and anxiety sensitivity in adolescents.

DESIGN AND METHODS

An online experimental design randomly exposed 233 Canadian youths aged 14-17 (83% female) to four videos of the Stress N' Go intervention (how to embrace stress) or to control condition videos (brain facts). Validated questionnaires assessing stress mindsets, perceived stress, and anxiety sensitivity were administered pre- and post-intervention, followed by open-ended questions.

RESULTS

The intervention content successfully instilled a stress-can-be-enhancing mindset compared to the control condition. Although Bayes factor analyses showed no main differences in perceived stress or anxiety sensitivity between conditions, a thematic analysis revealed that the intervention helped participants to live better with their stress.

CONCLUSIONS

Overall, these results suggest that our intervention can rapidly modify stress mindsets in youth. Future studies are needed to determine whether modifying stress mindsets is sufficient to alter anxiety sensitivity in certain adolescents and contexts.

A synthesis of evidence for policy from behavioural science during COVID-19

Scientific evidence regularly guides policy decisions1, with behavioural science increasingly part of this process2. In April 2020, an influential paper3 proposed 19 policy recommendations ('claims') detailing how evidence from behavioural science could contribute to efforts to reduce impacts and end the COVID-19 pandemic. Here we assess 747 pandemic-related research articles that empirically investigated those claims. We report the scale of evidence and whether evidence supports them to indicate applicability for policymaking. Two independent teams, involving 72 reviewers, found evidence for 18 of 19 claims, with both teams finding evidence supporting 16 (89%) of those 18 claims. The strongest evidence supported claims that anticipated culture, polarization and misinformation would be associated with policy effectiveness. Claims suggesting trusted leaders and positive social norms increased adherence to behavioural interventions also had strong empirical support, as did appealing to social consensus or bipartisan agreement. Targeted language in messaging yielded mixed effects and there were no effects for highlighting individual benefits or protecting others. No available evidence existed to assess any distinct differences in effects between using the terms 'physical distancing' and 'social distancing'. Analysis of 463 papers containing data showed generally large samples; 418 involved human participants with a mean of 16,848 (median of 1,699). That statistical power underscored improved suitability of behavioural science research for informing policy decisions. Furthermore, by implementing a standardized approach to evidence selection and synthesis, we amplify broader implications for advancing scientific evidence in policy formulation and prioritization.

A prosocial value intervention in gateway STEM courses

Many college students, especially first-generation and underrepresented racial/ethnic minority students, desire courses and careers that emphasize helping people and society. Can instructors of introductory science, technology, engineering, and math (STEM) courses promote motivation, performance, and equity in STEM fields by emphasizing the prosocial relevance of course material? We developed, implemented, and evaluated a prosocial utility-value intervention (UVI): A course assignment in which students were asked to reflect on the prosocial value of biology or chemistry course content; our focus was on reducing performance gaps between first-generation and continuing generation college students. In Studies 1a and 1b, we piloted two versions of a prosocial UVI in introductory biology (N = 282) and chemistry classes (N = 1,705) to test whether we could encourage students to write about the prosocial value of course content. In Study 2, we tested a version of the UVI that combines personal and prosocial values, relative to a standard UVI, which emphasizes personal values, using a randomized controlled trial in an introductory chemistry course (N = 2,505), and examined effects on performance and motivation in the course. In Study 3, we tested the prosocial UVI against a standard UVI in an introductory biology course (N = 712). Results suggest that the prosocial UVI may be particularly effective in promoting motivation and performance for first-generation college students, especially those who are more confident that they can perform well in the class, reflecting a classic expectancy-value interaction. Mediation analyses suggest that this intervention worked by promoting interest in chemistry. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Intraindividual Changes in Political Identity Strength (But Not Direction) Are Associated With Political Animosity in the United States and the Netherlands

We test if within-person changes in political identities are associated with within-person changes in political animosity in two longitudinal studies (United States N = 552, Waves = 26; Netherlands N = 1,670, Waves = 12). Typical studies examine cross-sectional associations without assessing within-person change. Our work provides a stronger test of the relationship. We find that within-person changes in the strength of people's ideological and partisan identities are associated with increased political animosity. We found no such associations with within-person changes in identity direction. These patterns were robust to covariates and emerged in both studies. In addition to these average effects, we found substantial heterogeneity across participants in the associations among identity strength, identity direction, and political animosity. We did not find robust and replicable moderators for this heterogeneity. These findings suggest that identity strength (but not identity direction) is a key, if heterogenous, factor in changes in political animosity.

Racial and Ethnic Representation in Preventive Intervention Research: a Methodological Study

Individuals who are Asian or Asian American, Black or African American, Native American or American Indian or Alaska Native, Native Hawaiian or Pacific Islander, and Hispanic or Latino (i.e., presently considered racial ethnic minoritized groups in the USA) lacked equal access to resources for mitigating risk during COVID-19, which highlighted public health disparities and exacerbated inequities rooted in structural racism that have contributed to many injustices, such as failing public school systems and unsafe neighborhoods. Minoritized groups are also vulnerable to climate change wherein the most severe harms disproportionately fall upon underserved communities. While systemic changes are needed to address these pervasive syndemic conditions, immediate efforts involve examining strategies to promote equitable health and well-being-which served as the impetus for this study. We conducted a descriptive analysis on the prevalence of culturally tailored interventions and reporting of sample characteristics among 885 programs with evaluations published from 2010 to 2021 and recorded in the Blueprints for Healthy Youth Development registry. Inferential analyses also examined (1) reporting time trends and (2) the relationship between study quality (i.e., strong methods, beneficial effects) and culturally tailored programs and racial ethnic enrollment. Two percent of programs were developed for Black or African American youth, and 4% targeted Hispanic or Latino populations. For the 77% of studies that reported race, most enrollees were White (35%) followed by Black or African American (28%), and 31% collapsed across race or categorized race with ethnicity. In the 64% of studies that reported ethnicity, 32% of enrollees were Hispanic or Latino. Reporting has not improved, and there was no relationship between high-quality studies and programs developed for racial ethnic youth, or samples with high proportions of racial ethnic enrollees. Research gaps on racial ethnic groups call for clear reporting and better representation to reduce disparities and improve the utility of interventions.

The direction of effects between parenting and adolescent affective well-being in everyday life is family specific

Numerous theories and empirical studies have suggested that parents and their adolescent children reciprocally influence each other. As most studies have focused on group-level patterns, however, it remained unclear whether this was true for every family. To investigate potential heterogeneity in directionality, we applied a novel idiographic approach to examine the effects between parenting and adolescent well-being in each family separately. For 100 days, 159 Dutch adolescents (Mage = 13.31, 62% female) reported on affective well-being and four parenting dimensions. The family-specific effects of pre-registered ( https://osf.io/7n2jx/ ) dynamic structural equation models indeed revealed that a reciprocal day-to-day association between parenting and adolescent affective well-being was present only in some families, with the proportion of families displaying a reciprocal association varying across the four parenting dimensions (11-55%). In other families, either parenting predicted the adolescent's affective well-being (8-43%) or vice versa (10-27%), or no day-to-day associations were found (16-60%). Adolescents with higher trait levels of environmental sensitivity and neuroticism were more strongly affected by parenting. Thus, findings suggest that the ways in which parents and adolescents influence each other in everyday life are unique, stressing the need to move towards an idiographic parenting science.

Causal complexity in human research: On the shared challenges of behavior genetics, medical genetics, and environmentally oriented social science

We received 23 spirited commentaries on our target article from across the disciplines of philosophy, economics, evolutionary genetics, molecular biology, criminology, epidemiology, and law. We organize our reply around three overarching questions: (1) What is a cause? (2) How are randomized controlled trials (RCTs) and within-family genome-wide association studies (GWASs) alike and unalike? (3) Is behavior genetics a qualitatively different enterprise? Throughout our discussion of these questions, we advocate for the idea that behavior genetics shares many of the same pitfalls and promises as environmentally oriented research, medical genetics, and other arenas of the social and behavioral sciences.

Methodological question-begging about the causes of complex social traits

Burt formulates her critique at a general level of abstraction that highlights the methodological deficiencies of sociogenomics without also calling attention to precisely the same deficiencies in the social science model she seeks to defend against its encroachments. What might have been a methodological bulwark against the excesses of sociogenomics is instead a one-sided critique that merely renews its charter.

Sexual self-efficacy and sexual communication among adolescent girls: moderated mediation results from a randomized controlled trial

OBJECTIVE

Guided by the Operating Conditions Framework, the goal of this study was to identify how and for whom an online sexual health program called Health Education and Relationship Training (HEART) worked.

DESIGN

Data come from a randomized controlled trial among 198 U.S. high school girls who completed HEART or an attention-matched control. We conducted mediation and moderated mediation models to determine if sexual self-efficacy was a mediator and if program acceptability and sexual activity status were moderators of HEART efficacy.

MAIN OUTCOME MEASURE

Sexual communication skills were assessed with a behavioral role-play task.

RESULTS

HEART significantly improved sexual communication skills. These effects were fully mediated through sexual self-efficacy. Specifically, HEART improved sexual self-efficacy which in turn increased sexual communication skills. Also, when participants liked the program more, the effect of HEART on sexual self-efficacy was stronger. Further, among girls who had engaged in sexual activity, sexual self-efficacy was significantly associated with sexual communication skills.

CONCLUSION

This study provides insights into the mechanisms of behavior change underlying HEART. Results highlight the need to further 'unpack' the effects of other sexual health programs, as we showed that programs may work better under certain conditions.

Mindset × Context: Schools, Classrooms, and the Unequal Translation of Expectations into Math Achievement

When do adolescents' dreams of promising journeys through high school translate into academic success? This monograph reports the results of a collaborative effort among sociologists and psychologists to systematically examine the role of schools and classrooms in disrupting or facilitating the link between adolescents' expectations for success in math and their subsequent progress in the early high school math curriculum. Our primary focus was on gendered patterns of socioeconomic inequality in math and how they are tethered to the school's peer culture and to students' perceptions of gender stereotyping in the classroom. To do this, this monograph advances Mindset × Context Theory. This orients research on educational equity to the reciprocal influence between students' psychological motivations and their school-based opportunities to enact those motivations. Mindset × Context Theory predicts that a student's mindset will be more strongly linked to developmental outcomes among groups of students who are at risk for poor outcomes, but only in a school or classroom context where there is sufficient need and support for the mindset. Our application of this theory centers on expectations for success in high school math as a foundational belief for students' math progress early in high school. We examine how this mindset varies across interpersonal and cultural dynamics in schools and classrooms. Following this perspective, we ask: 1. Which gender and socioeconomic identity groups showed the weakest or strongest links between expectations for success in math and progress through the math curriculum? 2. How did the school's peer culture shape the links between student expectations for success in math and math progress across gender and socioeconomic identity groups? 3. How did perceptions of classroom gender stereotyping shape the links between student expectations for success in math and math progress across gender and socioeconomic identity groups? We used nationally representative data from about 10,000 U.S. public school 9th graders in the National Study of Learning Mindsets (NSLM) collected in 2015-2016-the most recent, national, longitudinal study of adolescents' mindsets in U.S. public schools. The sample was representative with respect to a large number of observable characteristics, such as gender, race, ethnicity, English Language Learners (ELLs), free or reduced price lunch, poverty, food stamps, neighborhood income and labor market participation, and school curricular opportunities. This allowed for generalization to the U.S. public school population and for the systematic investigation of school- and classroom-level contextual factors. The NSLM's complete sampling of students within schools also allowed for a comparison of students from different gender and socioeconomic groups with the same expectations in the same educational contexts. To analyze these data, we used the Bayesian Causal Forest (BCF) algorithm, a best-in-class machine-learning method for discovering complex, replicable interaction effects. Chapter IV examined the interplay of expectations, gender, and socioeconomic status (SES; operationalized with maternal educational attainment). Adolescents' expectations for success in math were meaningful predictors of their early math progress, even when controlling for other psychological factors, prior achievement in math, and racial and ethnic identities. Boys from low-SES families were the most vulnerable identity group. They were over three times more likely to not make adequate progress in math from 9th to 10th grade relative to girls from high-SES families. Boys from low-SES families also benefited the most from their expectations for success in math. Overall, these results were consistent with Mindset × Context Theory's predictions. Chapters V and VI examined the moderating role of school-level and classroom-level factors in the patterns reported in Chapter IV. Expectations were least predictive of math progress in the highest-achieving schools and schools with the most academically oriented peer norms, that is, schools with the most formal and informal resources. School resources appeared to compensate for lower levels of expectations. Conversely, expectations most strongly predicted math progress in the low/medium-achieving schools with less academically oriented peers, especially for boys from low-SES families. This chapter aligns with aspects of Mindset × Context Theory. A context that was not already optimally supporting student success was where outcomes for vulnerable students depended the most on student expectations. Finally, perceptions of classroom stereotyping mattered. Perceptions of gender stereotyping predicted less progress in math, but expectations for success in math more strongly predicted progress in classrooms with high perceived stereotyping. Gender stereotyping interactions emerged for all sociodemographic groups except for boys from high-SES families. The findings across these three analytical chapters demonstrate the value of integrating psychological and sociological perspectives to capture multiple levels of schooling. It also drew on the contextual variability afforded by representative sampling and explored the interplay of lab-tested psychological processes (expectations) with field-developed levers of policy intervention (school contexts). This monograph also leverages developmental and ecological insights to identify which groups of students might profit from different efforts to improve educational equity, such as interventions to increase expectations for success in math, or school programs that improve the school or classroom cultures.

Misdiagnosing the problem of why behavioural change interventions fail

Routes to achieving any sort of meaningful success in the enterprise of behavioural change requires an understanding of the rate of failure, and why failures occur. This commentary shows that there is more to diagnosis of failures than fixating on micro- rather than the macro-level behaviours.

Wise interventions consider the person and the situation together

Chater & Loewenstein (C&L) ignore the long history by which social scientists have developed more nuanced and ultimately more helpful ways to understand the relationship between persons and situations. This tradition is reflected and advanced in a large literature on "wise" social-psychological or mindset interventions, which C&L do not discuss yet mischaracterize.

The Onset of the COVID-19 Pandemic Made People Feel Threatened, but Had a Limited Impact on Political Attitudes in the United States

We investigated if the COVID-19 pandemic's onset caused changes in political attitudes. Influential theories predict that the pandemic's onset will cause people to adopt more conservative attitudes, more culturally conservative attitudes, or more extreme attitudes. We comprehensively tested the external validity of these predictions by estimating the causal effect of the pandemic's onset on 84 political attitudes and eight perceived threats using fine-grained repeated cross-sectional data (Study 1, N = 232,684) and panel data (Study 2, N = 552) collected in the United States. Although the pandemic's onset caused feelings of threat, the onset only caused limited attitude change (six conservative shifts, four extremity shifts, 12 liberal shifts, 62 no change). Prominent theories of threat and politics did not make accurate predictions for this major societal threat. Our results highlight the necessity of testing psychological theories' predictive powers in real-life circumstances.

Thinking outside the ballot box

A deeply heterogeneous set of ideological cohorts have shaped the course of history. From anarchists and authoritarians to Zionists and Zapatistas, the expansive alphabet of politics demands an equally expansive psychological vocabulary to describe political belief systems. We propose that constructing such a vocabulary is best facilitated by decentering familiar models that emphasize psychological differences between leftists and rightists. Synthesizing recent developments in the fields of personality, political science, and psychopathology, we characterize individual variation in politics as high-dimensional, heterarchical, intrapersonally eclectic, and contextually shaped and activated. Developing a data-driven taxonomic model of political-psychological phenomena will help create a foundational base of knowledge within political psychology that is more rigorous, more replicable, and certainly richer to investigate.

Association between meaningful activities at home and subjective well-being in older adults with long-term care needs: A cross-sectional study

For this study, we examined whether engaging in meaningful activities at home is associated with subjective well-being (SWB) in older adults with long-term care needs according to their preference for going out. We distributed a self-administered questionnaire to long-term care facilities in Japan and performed a linear mixed-effects model regression analysis of the responses. The dependent variable was SWB, and the independent variables were the number of meaningful home activities, preference for going out, and the interaction between them. In our survey (n = 217), we found that both number of meaningful home activities (B = 0.43; 95%CI: 0.17, 0.70) and its interaction with preference (B = -0.43; 95%CI: -0.79, -0.08) were associated with SWB. These results suggest the importance of engaging in meaningful activities at home for older adults who do not prefer going out. We should encourage older adults to participate in activities that match their preference.

Improving the Generalizability of Behavioral Science by Using Reality Checks: A Tool for Assessing Heterogeneity in Participants' Consumership of Study Stimuli

In attempting to draw bigger conclusions, researchers in psychology open their labs to more diverse groups of people. Yet even the most far-reaching theories must be tested with specific stimuli, materials, and methodology. To the extent that a study's stimuli are familiar beyond the lab to groups of people writ large, an experiment is said to have mundane realism-a type of external validity. We propose that an experiment's stimuli will vary in their relevance to each individual participant (such as how much they consume the stimuli outside the lab) and can be assessed using a tool: reality checks. We found that accounting for a study's mundane realism, at the individual level, significantly altered a study's results-which we found to be the case in testing well-established findings in psychology and behavioral economics. Our work suggests that measuring mundane realism (in addition to creating it) is a useful way of testing effects in psychology among the participants for whom the studies' scenarios and decisions will matter most outside of the lab.

Parental intrusive homework support and math achievement: Does the child's mindset matter?

Prior research shows that when parents monitor, check, and assist in completing homework without an invitation, their children's motivation and academic achievement often decline. We propose that intrusive support from parents might also send the message that children are incompetent, especially if they believe their intelligence is fixed. We tested whether children's mindsets moderate the negative link between parents' intrusive homework support and achievement among first- and second-grade students followed for one academic year (Study 1, N = 563) and middle and high school students for two academic years (Study 2, N = 1,613). The samples were obtained from large urban areas in the United States. In both studies, intrusive homework support more strongly predicted a decrease in achievement over time for children with a fixed mindset. These findings suggest that the belief that intellectual ability cannot be changed may exacerbate the detrimental effects of uninvited help on academic work. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Within-Individual Variation in Cognitive Performance Is Not Noise: Why and How Cognitive Assessments Should Examine Within-Person Performance

Despite evidence that it exists, short-term within-individual variability in cognitive performance has largely been ignored as a meaningful component of human cognitive ability. In this article, we build a case for why this within-individual variability should not be viewed as mere measurement error and why it should be construed as a meaningful component of an individual's cognitive abilities. We argue that in a demanding and rapidly changing modern world, between-individual analysis of single-occasion cognitive test scores does not account for the full range of within-individual cognitive performance variation that is implicated in successful typical cognitive performance. We propose that short-term repeated-measures paradigms (e.g., the experience sampling method (ESM)) be used to develop a process account of why individuals with similar cognitive ability scores differ in their actual performance in typical environments. Finally, we outline considerations for researchers when adapting this paradigm for cognitive assessment and present some initial findings from two studies in our lab that piloted the use of ESM to assess within-individual cognitive performance variation.

Individual Responses versus Aggregate Group-Level Results: Examining the Strength of Evidence for Growth Mindset Interventions on Academic Performance

Mindset theory assumes that students' beliefs about their intelligence-whether these are fixed or can grow-affects students' academic performance. Based on this assumption, mindset theorists have developed growth mindset interventions to teach students that their intelligence or another attribute can be developed, with the goal of improving academic outcomes. Though many papers have reported benefits from growth mindset interventions, others have reported no effects or even detrimental effects. Recently, proponents of mindset theory have called for a "heterogeneity revolution" to understand when growth mindset interventions are effective and when-and for whom-they are not. We sought to examine the whole picture of heterogeneity of treatment effects, including benefits, lack of impacts, and potential detriments of growth mindset interventions on academic performance. We used a recently proposed approach that considers persons as effect sizes; this approach can reveal individual-level heterogeneity often lost in aggregate data analyses. Across three papers, we find that this approach reveals substantial individual-level heterogeneity unobservable at the group level, with many students and teachers exhibiting mindset and performance outcomes that run counter to the authors' claims. Understanding and reporting heterogeneity, including benefits, null effects, and detriments, will lead to better guidance for educators and policymakers considering the role of growth mindset interventions in schools.

Where and with whom does a brief social-belonging intervention promote progress in college?

A promising way to mitigate inequality is by addressing students' worries about belonging. But where and with whom is this social-belonging intervention effective? Here we report a team-science randomized controlled experiment with 26,911 students at 22 diverse institutions. Results showed that the social-belonging intervention, administered online before college (in under 30 minutes), increased the rate at which students completed the first year as full-time students, especially among students in groups that had historically progressed at lower rates. The college context also mattered: The intervention was effective only when students' groups were afforded opportunities to belong. This study develops methods for understanding how student identities and contexts interact with interventions. It also shows that a low-cost, scalable intervention generalizes its effects to 749 4-year institutions in the United States.

Identifying heterogeneity using recursive partitioning: evidence from SMS nudges encouraging voluntary retirement savings in Mexico

Individuals regularly struggle to save for retirement. Using a large-scale field experiment ( N = 97 , 149 ) in Mexico, we test the effectiveness of several behavioral interventions relative to existing policy and each other geared toward improving voluntary retirement savings contributions. We find that an intervention framing savings as a way to secure one's family future significantly improves contribution rates. We leverage recursive partitioning techniques and identify that the overall positive treatment effect masks subpopulations where the treatment is even more effective and other groups where the treatment has a significant negative effect, decreasing contribution rates. Accounting for this variation is significant for theoretical and policy development as well as firm profitability. Our work also provides a methodological framework for how to better design, scale, and deploy behavioral interventions to maximize their effectiveness.

What can machine learning teach us about habit formation? Evidence from exercise and hygiene

We apply a machine learning technique to characterize habit formation in two large panel data sets with objective measures of 1) gym attendance (over 12 million observations) and 2) hospital handwashing (over 40 million observations). Our Predicting Context Sensitivity (PCS) approach identifies context variables that best predict behavior for each individual. This approach also creates a time series of overall predictability for each individual. These time series predictability values are used to trace a habit formation curve for each individual, operationalizing the time of habit formation as the asymptotic limit of when behavior becomes highly predictable. Contrary to the popular belief in a "magic number" of days to develop a habit, we find that it typically takes months to form the habit of going to the gym but weeks to develop the habit of handwashing in the hospital. Furthermore, we find that gymgoers who are more predictable are less responsive to an intervention designed to promote more gym attendance, consistent with past experiments showing that habit formation generates insensitivity to reward devaluation.