Salutogenic health measures: Psychometric properties of the Danish versions of the Flourish Index and the Secure Flourish Index.

Measurement of human flourishing represents a salutogenic approach to epidemiological and behavioral research emphasizing factors contributing to "good lives" rather than pathology. The objective of this study was to translate and psychometrically test the 10-item Flourish Index (FI) and 12-item Secure Flourish Index (SFI) in a convenience sample of Danish adults. A total of 325 participants completed a cross-sectional survey, with 148 of those participants completing the survey a second time (retest). Confirmatory factor analysis in a structural equation modelling framework was used to establish structural validity by comparing four different pre-specified models of the indexes. Additionally, internal consistency, convergent and incremental validity, and retest reliability were examined. The FI models exhibited superior structural validity compared with similar models of the SFI, although all models had good fits. Internal consistencies with McDonald's omega were 0.89 and 0.87 for the FI and SFI, respectively. The five (FI) or six (SFI) domains were happiness & life satisfaction, mental & physical health, meaning & purpose, character & virtue, close social relationships, and financial & material stability (λ4 = 0.51-0.91). Convergent and incremental validity tests supported predefined hypotheses. Retest analyses with the FI and SFI showed a high degree of retest reliability. Based on the psychometric evidence reported in this study, the Danish Flourish Index and Secure Flourish Index seem suitable for use with healthy adult Danes. The authors hope that this psychometric evaluation of the FI and SFI will stimulate research on patterns, health and economic outcomes, and predictors of human flourishing in Denmark.

Prospective associations of multidimensional well-being with work distraction and job satisfaction: a two-wave study of US employees.

Previous studies on the associations between well-being and work outcomes, such as work distraction and job satisfaction, have largely been cross-sectional and typically focused on only one or two aspects of well-being. Using two waves of data from a sample of employees at a United States health insurance company (n = 1,234), the present brief research report examines prospective associations between six domains of well-being (emotional health, physical health, meaning & purpose, character strengths, social connectedness, and financial security) and two work outcomes (work distraction and job satisfaction). Lagged regression analyses provided some evidence indicating that higher-level well-being in several domains was associated with subsequent reduced work distraction and increased job satisfaction assessed approximately 1 year later, but the magnitude of associations with each outcome did vary by specific domain. Emotional health and social connectedness were most strongly associated with work distraction and job satisfaction. We discuss some implications of the findings, including the importance of applying a multidimensional approach to studying employee well-being and potential opportunities for organizations to support the well-being of their employees.

Reliability and Validity of a Multidimensional Measure of Subjective Community Well-Being.

An individual's flourishing is sustained by and dependent on their community's well-being. We provide one of the first studies of a measure of communal subjective well-being, focusing on individuals' relationships with their community. Using two samples from the Greater Columbus, Ohio region, we provide evidence of the reliability and validity of the Subjective Community Well-being (SCWB) assessment. The five domains of the SCWB are Good Relationships (α = .92), Proficient Leadership (α = .93), Healthy Practices (α = .92), Satisfying Community (α = .88), and Strong Mission (α = .81). A community-based sample (N = 1,435) and an online sample of Columbus residents (N = 692) were scored on the SCWB and compared across domains. We found evidence that the SCWB scores differentiate between active and less active community members. We discuss the appropriate uses of the SCWB as a measure of well-being and provide recommendations for research that could profitably utilize the SCWB measure to examine community well-being.

A brief measure of complete subjective well-being in Germany: A population-based validation of a German version of the Flourish Index (FI) and the Secure Flourish Index (SFI).

Measuring subjective well-being in a multidimensional, valid, reliable, and parsimonious way is important for both social science research and social policy. Here, we present an efficient measure of distinct domains of subjective well-being and overall flourishing. The Flourishing Index (FI) consists of five sub-domains: 1. happiness and life satisfaction, 2. physical and mental health, 3. meaning and purpose, 4. character and virtue, and 5. close social relationships. The Secure Flourishing Index (SFI) adds the sub-domain financial and material stability, which is thought to be necessary to sustain the other domains over time. We developed a German version of these measures in a multi-stage translation and scale testing process. The results of an exploratory factor analysis in Study 1 (N = 192) suggest a unidimensional structure of the FI and a two-dimensional structure of the SFI. Moreover, both indices (and most sub-domains) revealed acceptable to good reliability. The factor structures were confirmed in Study 2 (N = 13,268). We provide indications for measurement invariance of both indices with regard to gender and age. We furthermore examined inter-correlations with related constructs such as importance of health, self-efficacy, and social support. Study 3 (N = 317) finds evidence for high convergent validity of both the FI and the SFI with overall well-being as well as sub-scores of the PERMA-Profiler. These results suggest that the FI and the SFI are efficient measures of distinct domains of subjective well-being and overall flourishing. Our translation of the FI and SFI, along with the empirical relationships that we found among the measures that we reviewed, will help scholars in Germany (and beyond) explore an expanded range of domains of well-being, including the comparatively neglected domains of character and virtue, physical health, and financial and material stability.

Differences in Multi-Dimensional Well-Being Among Factory Workers: Evidence from Six Countries.

This paper presents cross-cultural comparisons of well-being among factory workers, as measured by the six well-being domains of happiness and life satisfaction, physical and mental health, meaning and purpose, character and virtue, close social relationships, and financial and material stability. Relative ranks of well-being domains across examined groups of workers are also compared. Results are based on survey data from factory workers in Cambodia, China, Mexico, Poland, Sri Lanka, and the United States. Average well-being scores are higher among factory workers in Mexico, China, and Cambodia than in the U.S., Poland, and Sri Lanka across all domains except financial and material stability. Close social relationships were the highest ranked domain in Cambodia and China but ranked much lower (5th) in the U.S. Meaning and purpose, as well as character and virtue were highly ranked across the board. Strong social relationships seem to thrive in contexts where financial insecurity is high.

Informal Helping and Subsequent Health and Well-Being in Older U.S. Adults.

BACKGROUND: Growing evidence suggests that informal helping (unpaid volunteering not coordinated by an organization or institution) is associated with improved health and well-being outcomes. However, studies have not investigated whether changes in informal helping are associated with subsequent health and well-being. METHODS: This study evaluated if changes in informal helping (between t0;2006/2008 and t1;2010/2012) were associated with 35 indicators of physical, behavioral, and psychosocial health and well-being (at t2;2014/2016) using data from 12,998 participants in the Health and Retirement study - a national cohort of US adults aged > 50. RESULTS: Over the four-year follow-up period, informal helping ≥ 100 (versus 0) hours/year was associated with a 32% lower mortality risk (95% CI [0.54, 0.86]), and improved physical health (e.g., 20% reduced risk of stroke (95% CI [0.65, 0.98])), health behaviors (e.g., 11% increased likelihood of frequent physical activity (95% CI [1.04, 1.20])), and psychosocial outcomes (e.g., higher purpose in life (ß = 0.15, 95% CI [0.07, 0.22])). However, there was little evidence of associations with various other outcomes. In secondary analyses, this study adjusted for formal volunteering and a variety of social factors (e.g., social network factors, receiving social support, and social participation) and results were largely unchanged. CONCLUSIONS: Encouraging informal helping may improve various aspects of individuals' health and well-being and also promote societal well-being.

Working from home and subsequent work outcomes: Pre-pandemic evidence.

Frequent working from home (WFH) may stay as a new work norm after the COVID-19 pandemic. Prior observational studies on WFH and work outcomes under non-pandemic circumstances are mostly cross-sectional and often studied employees who worked from home in limited capacity. To provide additional insights that might inform post-pandemic work policies, using longitudinal data collected before the COVID-19 pandemic (June 2018 to July 2019), this study aims to examine the associations between WFH and multiple subsequent work-related outcomes, as well as potential modifiers of these associations, in a sample of employees among whom frequent or even full-time WFH was common (N = 1,123, Meanage = 43.37 years). In linear regression models, each subsequent work outcome (standardized score was used) was regressed on frequencies of WFH, adjusting for baseline values of the outcome variables and other covariates. The results suggested that WFH for 5 days/week versus never WFH was associated with subsequently less work distraction (ß = -0.24, 95% CI = -0.38, -0.11), greater perceived productivity/engagement (ß = 0.23, 95% CI = 0.11, 0.36), and greater job satisfaction (ß = 0.15, 95% CI = 0.02, 0.27), and was associated with subsequent work-family conflicts to a lesser extent (ß = -0.13, 95% CI = -0.26, 0.004). There was also evidence suggesting that long work hours, caregiving responsibilities, and a greater sense of meaningful work can all potentially attenuate the benefits of WFH. As we move towards the post-pandemic era, further research will be needed to understand the impacts of WFH and resources for supporting employees who work from home.

Evidence for concealed fasciculo-ventricular connections as revealed by His bundle pacing.

BACKGROUND: It is almost 100 years ago since Mahaim described the so-called paraspecific connections between the ventricular conduction axis and the crest of the muscular ventricular septum, believing such pathways to be ubiquitous. These pathways, however, have yet to be considered as potential pathways for septal activation during His bundle pacing. MATERIALS: So as to explore the hypothesis that specialised septal pathways might provide the substrate for septal activation during His bundle pacing, we compared the findings from 22 serially sectioned histological datasets and 34 different individuals undergoing His bundle pacing. RESULTS: We found histologically specialised pathways connecting the branching component of the atrioventricular conduction axis with the crest of the muscular ventricular septum in almost four-fifths of the histological datasets. In 32 of 34 patients undergoing His bundle pacing, the QRS complex closely resembled published images of known conduction through fasciculo-ventricular pathways. In only two patients was a delta wave not seen at any pacing voltages. Capture of these connections varied according to pacing voltage, a finding which correlated with the distance of the pathways from the site of penetration of the ventricular conduction axis. Ventricular activation times remained normal in the presence of the delta wave at higher pacing voltage but were prolonged at lower voltages. CONCLUSIONS: Our histologic findings confirm fasciculo-ventricular connections, initially described by Mahaim as being paraspecific, are likely ubiquitous. Analysis of 12-lead electrocardiograms leads us to conclude that fasciculo-ventricular pathways, concealed during sinus rhythm, become manifest with His bundle pacing.

Psychological caring climate at work, mental health, well-being, and work-related outcomes: Evidence from a longitudinal study and health insurance data.

Psychological climate for caring (PCC) is a psychosocial factor associated with individual work outcomes and employee well-being. Evidence on the impacts of various psychological climates at work is based mostly on self-reported health measures and cross-sectional data. We provide longitudinal evidence on the associations of PCC with subsequent diagnosed depression and anxiety, subjective well-being, and self-reported work outcomes. Employees of a US organization with a worker well-being program provided data for the analysis. Longitudinal survey data merged with data from personnel files and health insurance claims records comprising medical information on diagnosis of depression and anxiety were used to regress each outcome on PCC at baseline, adjusting for prior values of all outcomes and other covariates. PCC was found to be associated with lower odds of subsequent diagnosed depression, an increase in overall well-being, mental health, physical health, social connectedness, and financial security, as well as a decrease in distraction at work, an increase in productivity/engagement and possibly in job satisfaction. There was little evidence of associations between PCC and subsequent diagnosed anxiety, character strengths, and work-family conflict. Work policies focused on improving PCC may create a promising pathway to promoting employee health and well-being as well as improving work-related outcomes.

Associations of online religious participation during COVID-19 lockdown with subsequent health and well-being among UK adults.

BACKGROUND: In-person religious service attendance has been linked to favorable health and well-being outcomes. However, little research has examined whether online religious participation improves these outcomes, especially when in-person attendance is suspended. METHODS: Using longitudinal data of 8951 UK adults, this study prospectively examined the association between frequency of online religious participation during the stringent lockdown in the UK (23 March -13 May 2020) and 21 indicators of psychological well-being, social well-being, pro-social/altruistic behaviors, psychological distress, and health behaviors. All analyses adjusted for baseline socio-demographic characteristics, pre-pandemic in-person religious service attendance, and prior values of the outcome variables whenever data were available. Bonferroni correction was used to correct for multiple testing. RESULTS: Individuals with online religious participation of ≥1/week (v. those with no participation at all) during the lockdown had a lower prevalence of thoughts of self-harm in week 20 (odds ratio 0.24; 95% CI 0.09-0.62). Online religious participation of <1/week (v. no participation) was associated with higher life satisfaction (standardized ß = 0.25; 0.11-0.39) and happiness (standardized ß = 0.25; 0.08-0.42). However, there was little evidence for the associations between online religious participation and all other outcomes (e.g. depressive symptoms and anxiety). CONCLUSIONS: There was evidence that online religious participation during the lockdown was associated with some subsequent health and well-being outcomes. Future studies should examine mechanisms underlying the inconsistent results for online v. in-person religious service attendance and also use data from non-pandemic situations.

Prospective associations between strengths of moral character and health: longitudinal evidence from survey and insurance claims data.

PURPOSE: Excellent character, reflected in adherence to high standards of moral behavior, has been argued to contribute to well-being. The study goes beyond this claim and provides insights into the role of strengths of moral character (SMC) for physical and mental health. METHODS: This study used longitudinal observational data merged with medical insurance claims data collected from 1209 working adults of a large services organization in the US. Self-reported physical and mental health as well as diagnostic information on depression, anxiety, and cardiovascular disease were used as outcomes. The prospective associations between SMC (7 indicators and a composite measure) and physical and mental health outcomes were examined using lagged linear and logistic regression models. A series of sensitivity analyses provided evidence for the robustness of results. RESULTS: The results suggest that persons who live their life according to high moral standards have substantially lower odds of depression (by 21-51%). The results were also indicative of positive associations between SMC and self-reports of mental health (ß = 0.048-0.118) and physical health (ß = 0.048-0.096). Weaker indications were found for a protective role of SMC in mitigating anxiety (OR = 0.797 for the indicator of delayed gratification) and cardiovascular disease (OR = 0.389 for the indicator of use of SMC for helping others). CONCLUSIONS: SMC may be considered relevant for population mental health and physical health. Public health policies promoting SMC are likely to receive positive reception from the general public because character is both malleable and aligned with the nearly universal human desire to become a better person.

Demographic Predictors of Complete Well-Being.

This paper examines demographic differences in flourishing, defined as "complete well-being" and consisting of six domains: emotional health, physical health, purpose, character strengths, social connectedness, and financial security. Results are based on a random, cross-sectional sample of 2363 survey respondents drawn from employees of a large, national, self-insured employer based in the United States. We found that well-being across domains tends to increase with age, although there are some variations. Results are similar across most domains for men and women, although women score higher on character strengths, while men had higher scores on financial security. Racial and ethnic differences were striking. Black employees score higher than the reference group (White employees) on the emotional, purpose, and character strengths domains, but considerably lower on financial security. Hispanics also score lower on financial security (though not as low as Blacks), but higher than Whites on purpose, character strengths, and social connectedness. Asians reported higher well-being than Whites across all domains except purpose.

Identifying pathways to increased volunteering in older US adults.

While growing evidence documents strong associations between volunteering and improved health and well-being outcomes, less is known about the health and well-being factors that lead to increased volunteering. Using data from 13,771 participants in the Health and Retirement Study (HRS)-a diverse, longitudinal, and national sample of older adults in the United States-we evaluated a large range of candidate predictors of volunteering. Specifically, using generalized linear regression models with a lagged exposure-wide approach, we evaluated if changes in 61 predictors spanning physical health, health behaviors, and psychosocial well-being (over a 4-year follow-up between t0; 2006/2008 and t1; 2010/2012) were associated with volunteer activity four years later (t2; 2014/2016). After adjusting for a rich set of covariates, certain changes in some health behaviors (e.g., physical activity ≥ 1x/week), physical health conditions (e.g., physical functioning limitations, cognitive impairment), and psychosocial factors (e.g., purpose in life, constraints, contact with friends, etc.) were associated with increased volunteering four years later. However, there was little evidence that other factors were associated with subsequent volunteering. Changes in several indicators of physical health, health behaviors, and psychosocial well-being may predict increased volunteering, and these factors may be novel targets for interventions and policies aiming to increase volunteering in older adults.

Prospective Associations Between Social Connectedness and Mental Health. Evidence From a Longitudinal Survey and Health Insurance Claims Data.

Objectives: Evidence on social stimuli associated with mental health is based mostly on self-reported health measures. We aimed to examine prospective associations between social connectedness and clinical diagnosis of depression and of anxiety. Methods: Longitudinal observational data merged with health insurance data comprising medical information on diagnosis of depression and anxiety were used. 1,209 randomly sampled employees of a US employer provided data for the analysis. Robust Poisson regression models were used. Multiple imputation was conducted to handle missing data on covariates. Results: Better social connectedness was associated with lower risks of subsequently diagnosed depression and anxiety, over a one-year follow-up period. Reports of feeling lonely were associated with increased risks of depression and anxiety. Association between community-related social connectedness and subsequent diagnosis of depression, but not of anxiety, was found. The associations were independent of demographics, socioeconomic status, lifestyle, and work characteristics. They were also robust to unmeasured confounding, missing data patterns, and prior health conditions. Conclusion: Social connectedness may be an important factor for reducing risks of depression and anxiety. Loneliness should be perceived as a risk factor for depression and anxiety.

Promoting Resilience and Flourishing Among Older Adult Residents in Community Living: A Feasibility Study.

BACKGROUND AND OBJECTIVES: The Stress Management and Relaxation Training-Relaxation Response Resiliency Program (SMART-3RP) is a mind-body group intervention that integrates relaxation training with cognitive behavioral and positive psychology techniques. This study assessed SMART-3RP feasibility, acceptability, and preliminary efficacy for enhancing resilience and flourishing among older adults in continuing care retirement communities (CCRCs). RESEARCH DESIGN AND METHODS: We conducted a prospective single-arm study of SMART-3RP groups delivered by clinicians at 4 CCRCs (n = 80). Eligible residents lived in community apartments. Participants completed pre- and postintervention surveys. We evaluated attendance (hypothesis: ≥60% attend ≥6 of 9 sessions), enrollment, and retention. Mixed methods were used to explore acceptability. Paired samples t-tests were conducted to explore changes in resilience, flourishing, and key intervention targets. RESULTS: From March to June 2021, we screened 89 residents with 87 (98%) consenting to participate and 80 (90%) enrolling in the study. Among 80 participants (85% female; 98% non-Hispanic White; M age = 80 years [SD = 6]), 88% attended ≥6 sessions, and 89% completed the postintervention survey. Participants found meaning in participation and practiced skills in the context of challenges such as caregiving burden or bereavement. Survey results, showing increases in resilience, flourishing, and several intervention targets, aligned with participants' perceived intervention value. DISCUSSION AND IMPLICATIONS: SMART-3RP was feasible and acceptable for CCRC residents; participants perceived value in practicing mind-body strategies in a group-based setting. Preliminary evidence suggested a pattern of improvements in resilience, flourishing, and intervention targets. Findings provide insights for mind-body interventions and recommendations for adaptations to late-in-life concerns and community settings. CLINICAL TRIALS REGISTRATION NUMBER: NCT04720014.

Global Trends of Mean and Inequality in Multidimensional Wellbeing: Analysis of 1.2 Million Individuals From 162 Countries, 2009-2019.

INTRODUCTION: Human flourishing is a multidimensional concept characterized by a state of complete wellbeing. However, much of the prior research on wellbeing has principally focused on population averages assessed using a single item of wellbeing. This study examined trends in population averages and inequalities for a multidimensional index of wellbeing and compared emergent patterns with those found for Cantril's ladder, a measure of life satisfaction commonly used as a unidimensional index of wellbeing. METHODS: Data were from the Gallup World Poll from the years 2009 to 2019, a repeated cross-sectional survey of nationally representative samples comprising ~1.2 million individuals from 162 countries. We assessed five domains of flourishing: (1) happiness, (2) health, (3) purpose, (4) character, and (5) social relationships. We used the Gini Index to estimate inequalities in wellbeing within populations. We examined and compared country ranking, global and region-specific trajectories of mean and inequality, and relationships with age for flourishing and Cantril's ladder. RESULTS: Although all trends were highly correlated across the two metrics of wellbeing, we identified distinct patterns in flourishing concerning geography, time, and age relationships that were not observed for Cantril's ladder. Temporal trends and age relationships were different across domains of flourishing. Evidence of changing inequalities in wellbeing was also found, even when population averages were high or stable over time. CONCLUSION: Comprehensive measures of wellbeing are needed to capture the complex and changing patterns of wellbeing both within and across populations.

Rivaroxaban as Therapy for Saphenous Venous Graft Failure due to Venous Outflow Mismatch.

Background: Recurrent angina and long-term occlusion following coronary artery bypass graft surgery is often treated with percutaneous coronary intervention, a high-risk intervention for distal embolization. Here, we present the utilization of the novel oral anticoagulant, rivaroxaban, in the treatment of saphenous vein graft thrombosis with complete resolution of the thrombus secondary to graft outflow mismatch. Case Presentation. A 69-year-old man with triple coronary artery bypass grafting using a saphenous vein and left internal mammary artery, performed in 2017, presented at our hospital for recurrent angina. Coronary angiography revealed a patent LIMA to LAD and a large clot burden in the venous conduit to the first OM/terminal circumflex-theorized to be due to an outflow mismatch of the large saphenous vein to the native artery resulting in stasis. Instead of percutaneous coronary intervention, he was treated with rivaroxaban 20 mg once a day. The angiography 4 weeks after starting rivaroxaban showed complete resolution of the thrombus. Conclusion: Rivaroxaban could become a potential treatment option in thrombus reversal due to static venous flow with subsequent long-term patency of the graft. Additionally, its use may be indicated in the generalized prevention of VGF.

Longitudinal associations between domains of flourishing.

The longitudinal interrelationships between domains of human well-being or flourishing remain understudied empirically. While different aspects of flourishing may be sought as their own end, it is also the case that well-being in one domain may influence well-being in other domains. Using longitudinal data form a sample of employees from a large national employer in the United States (N = 1209, mean age = 43.52 years, age range 20-74 years), this study examined the temporal associations between various domains of flourishing, based on a 40-item index that assessed six domains of flourishing. These domains include emotional health, physical health, meaning and purpose, character strengths, social connectedness, and financial security. A set of linear regression models were used to regress subsequent composite flourishing on flourishing domain-specific scores at baseline. The results indicated that all domains were each independently associated with greater composite flourishing subsequently. The strongest and most robust links were observed for meaning and purpose (ß = 0.19, 95% confidence interval [CI] 0.13, 0.25), social connectedness (ß = 0.17, 95% CI 0.12, 0.22), and financial security (ß = 0.32, 95% CI 0.28, 0.37). Further analyses that regressed subsequent composite flourishing on individual item indicators at baseline suggested that, out of all 40 items, one item under the character domain "I always act to promote good in all circumstances, even in difficult and challenging situations" and one item in the physical health domain ("Based on my past health, I expect to be healthy long into the future") had the most robust association with subsequent composite flourishing. Implications of these results for understanding the constituents of a flourishing life and for refinement of the flourishing assessments are discussed.

Guidelines and standards for the study of death and recalled experiences of death--a multidisciplinary consensus statement and proposed future directions.

An inadvertent consequence of advances in stem cell research, neuroscience, and resuscitation science has been to enable scientific insights regarding what happens to the human brain in relation to death. The scientific exploration of death is in large part possible due to the recognition that brain cells are more resilient to the effects of anoxia than assumed. Hence, brain cells become irreversibly damaged and "die" over hours to days postmortem. Resuscitation science has enabled life to be restored to millions of people after their hearts had stopped. These survivors have described a unique set of recollections in relation to death that appear universal. We review the literature, with a focus on death, the recalled experiences in relation to cardiac arrest, post-intensive care syndrome, and related phenomena that provide insights into potential mechanisms, ethical implications, and methodologic considerations for systematic investigation. We also identify issues and controversies related to the study of consciousness and the recalled experience of cardiac arrest and death in subjects who have been in a coma, with a view to standardize and facilitate future research.

Social ascent changes cognition, behaviour and physiology in a highly social cichlid fish.

When an individual ascends in dominance status within their social community, they often undergo a suite of behavioural, physiological and neuromolecular changes. While these changes have been extensively characterized across a number of species, we know much less about the degree to which these changes in turn influence cognitive processes like associative learning, memory and spatial navigation. Here, we assessed male Astatotilapia burtoni, an African cichlid fish known for its dynamic social dominance hierarchies, in a set of cognitive tasks both before and after a community perturbation in which some individuals ascended in dominance status. We assayed steroid hormone (cortisol, testosterone) levels before and after the community experienced a social perturbation. We found that ascending males changed their physiology and novel object recognition preference during the perturbation, and they subsequently differed in social competence from non-ascenders. Additionally, using a principal component analysis we were able to identify specific cognitive and physiological attributes that appear to predispose certain individuals to ascend in social status once a perturbation occurs. These previously undiscovered relationships between social ascent and cognition further emphasize the broad influence of social dominance on animal decision-making. This article is part of the theme issue 'The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies'.