Nomological Network of Dispositional Mindfulness: Evidence from MIDUS-II and MIDUS-III

While dispositional mindfulness is a popular construct in the field of positive psychology, its nomological network in the context of health and well-being is not well established. Our study addresses this limitation by examining the relationship between dispositional mindfulness and various health-related psychological constructs, including personality, social well-being, and affective states. Data for this study were gathered from the national longitudinal studies of health and well-being called Midlife in the United States (MIDUS-II and MIDUS-III). The nomological network analysis of dispositional mindfulness showed positive associations with both religiosity and overall well-being measures (e.g., Social Well-Being, Sympathy, Optimism, and Generativity) and negative associations with maladaptive tendencies (e.g., Pessimism, Aggression, Neuroticism, and Personal Constraints). Finally, test-retest validity was positively verified by significant correlations among the variables, spanning over ten years. Articulating a nomological network of dispositional mindfulness has important implications for future research and practice.


Introduction
The concept of mindfulness (i.e., the nonjudgmental awareness of one's internal or external environment) has been a core component in Buddhist meditative traditions (Brown, Ryan, & Crosswell, 2007). Ven. Analayo, in his book called Satipattinata: The direct path to realization (2003), described mindfulness as seeing things just as they are, unadulterated by habitual reactions and projections. There has been significant growth in mindfulness research in the last 30 years or so, spanning fields as diverse as religious studies, neuroscience, clinical and positive psychology (Williams & Kabat-Zinn, 2011). Mindfulness or its lack thereof is relevant to a diverse range of psychopathological and health-related outcomes as well. The potential benefits of mindfulness-based interventions have garnered the attention of researchers and clinical practitioners encompassing psychology and neuroscience (Chiesa & Serretti, 2011. Despite a wealth of research, the field of mindfulness remains in its adolescence. For example, although many studies have examined this construct in relation to various outcomes of interest, the systematic investigation of the nomological network of dispositional mindfulness is lacking. Nomological networks specify patterns of relations among constructs (Cronbach & Meehl, 1955). Individual studies have frequently reported associations of dispositional mindfulness with specific trait and state factors. However, research has not explored the nomological network of dispositional mindfulness across various self-report measures on a scientific level. It appears that no study has simultaneously assessed convergent and discriminant relationships of dispositional mindfulness with other potentially related psychological constructs.
Endeavors to define and measure mindfulness have not been without controversy. The research has exposed significant disagreements, specifically about where and how a "true" understanding of mindfulness is to be found (Brown et al., 2007). Thus, there is a clear need for research that comprehensively establishes the convergent and discriminant validity of dispositional mindfulness. As a nomological network of dispositional mindfulness is not well established, the current study addresses this limitation by examining the relationships of dispositional mindfulness with various widely used self-reported psychological measures that have implications for health and well-being. Specifically, this study seeks to establish relationships of dispositional mindfulness with a variety of personality, affective (e.g., positive affect, negative affect, perceived stress), psychopathological, and other psychological variables. To establish the nomological network surrounding dispositional mindfulness, we used samples from the United States spanning two different points in time (about ten years apart), using MIDUS-II and MIDUS-III datasets. Because the groups represent two time periods, consistency across samples would increase confidence that the results are not merely local phenomena.

Background of Mindfulness Research
Mindfulness, which can be broadly understood as (1) the ongoing monitoring of present-moment experience (2) with an orientation of acceptance (Lindsay & Crosswell, 2016), has generated a great deal of research in academic and applied psychology. According to Brown et al. (2007), mindfulness is thought to have been primarily developed from Buddhist traditions and several other philosophical and psychological traditions (e.g., ancient Greek philosophy, existentialism, transcendentalism, humanism, and naturalism). An early definition of mindfulness that continues to be useful and widely accepted among clinicians and researchers was established by Kabat-Zinn (1994), who defined mindfulness as intentional, nonjudgmental attention. More recently, Bishop et al. (2004) proposed a two-factor model of mindfulness composed of self-regulation of attention to maintain focus on the present experience and a purposeful orientation toward the present moment that includes non-striving. Therefore, of particular relevance to both the conceptualization and operationalization of mindfulness is the "non-judgment" or "receptive awareness or acceptance" as a path toward a centered and integrated way of being.
In general, mindfulness includes awareness and openness to the present moment. Langer and Moldoveanu (2000) extended the definition of mindfulness to include an environmental and problem-solving approach, presenting individuals with enhanced sensitivity to all of their available options. Mindfulness describes a quality of awareness that potentiates or creates the fertile conditions necessary for more integrated self-regulation. Currently, there are two main narratives of mindfulness. One is that of Buddhist meditative traditions and is often described as paying attention in a particular way, purposefully, in the present moment, and nonjudgmentally (Kabat-Zinn, 1994). Recent studies investigating mindfulness and various meditative techniques have shown great promise for clinical applications as well, especially in the area of stress reduction and the treatment of various mental health disorders (Keng, Smoski, & Robins, 2011) as well as in the state of self-esteem (Pepping, O'Donovan, & Davis, 2013).
interests, it is preceded by the rich "inner science" (Cabezon, 2003) developed over many centuries in the Buddhist traditions. Wallace (2003) suggests a deep complementarity between Western scientific and Buddhist contemplative approaches to the study of the mind and behavior. The methods employed by each approach differ, as one is experimental, and the other is experiential. Still, the refinement of attention cultivated in Buddhist contemplative practices has made it a powerful tool for the direct observation of the mind and behavior. In this sense, Buddhism represents a mode of inquiry bridging rigorous logical analysis (as in philosophy) and empirical investigation (as in science) (Wallace, 2003).
State mindfulness has been conceptualized as a state practiced in mindfulness meditation (e.g., Lau et al., 2006) and as a trait of one's predisposition to be mindful in daily life (e.g., Baer, Smith, Hopkins, Krietemeyer, & Toney, 2006). Measures of trait or dispositional mindfulness typically concern the general cross-situational frequency of mindful states over time. A study by Kiken, Garland, Bluth, Palsson and Gaylord (2015) found that heightening state mindfulness in meditation practice over time increases trait mindfulness, even though individuals' trajectories of change may vary. Most measures of mindfulness focus on one's predisposition to being mindful in daily life rather than the particular mindful state at the time of measurement. Studies found that dispositional mindfulness has positive relationships with working memory and sustained attention (Ruocco & Wonders, 2013) and negative relationships with perceived stress and stress-related symptoms (Roberts & Danoff-Burg, 2010). Mindfulness has also been found to be positively related to psychological well-being (Brown et al., 2007) and inversely associated with a wide range of problematic psychological outcomes, including anxiety and depression (Roemer et al., 2009) and general distress in life (Masuda & Tully, 2012).

The Present Study
The present investigation examines the nomological network of dispositional mindfulness in the theoretical and empirical relations with other constructs. Exploring a theory's nomological network helps establish construct validity. Aside from addressing validity issues, our current research will also help enhance understanding of how mindfulness fits into the nomological network of other established indices of attention. Specifically, the present study examines both convergent and discriminant construct validity evidence for a commonly used self-report measure of dispositional mindfulness. In doing so, mindfulness will be placed within the broader nomological network related to individual-level psychological variables associated with health and well-being. Also, preliminary explanations will be presented regarding how mindfulness converges with and discriminates from existing constructs in the field of psychology. Whether dispositional mindfulness predicts theoretically expected outcomes is a key issue concerning its construct validity and research and clinical value.
Our study examines whether trait (dispositional) mindfulness is associated positively or negatively with various traits in cognitive, affective, and mental/physical health domains. Elucidating whether individual differences in mindfulness are related to well-established psychological constructs can inform our understanding of the value of sustained mindful states. Our goal is to investigate whether a self-report measure of dispositional mindfulness is related to a broad range of health-related behavioral and psychological traits in theoretically expected directions. Based on past literature, we predicted that dispositional mindfulness would be positively associated with adaptive psychological functioning and negatively associated with maladaptive psychological functioning. Creating ways to assess and validate the construct of dispositional mindfulness is essential for designing corresponding interventions focused on health and well-being.

Participant Selection
Participants were part of a national longitudinal study of health and well-being funded by the National Institute on Aging called Midlife in the United States (MIDUS). MIDUS was initiated as MIDUS-I in 1995 with a survey of approximately 7,000 English-speaking adults of both sexes between the ages of 25 and 74 years. As a follow-up study, MIDUS-II was conducted approximately ten years later using the same respondents, with data collected from 2004 to 2006 and a mortality-adjusted response rate of 75%. MIDUS-II respondents were aged 35 to 86. Data collection largely repeated baseline assessments (i.e., phone interview and extensive self-administered questionnaire), with additional questions in selected areas (e.g., cognitive functioning, optimism and coping, stressful life events, and caregiving). Overall, complete data were collected from nearly 5,900 individuals.
MIDUS-III was then conducted in 2013 and 2014. Participants were assessed through phone interviews and self-administered questionnaires. The data focused on behavioral, psychological, and social factors as well as physical and mental health. In our study, we used the MIDUS-II and MIDUS-III data sets. Both these rounds of the MIDUS survey included all of the following scales and response options. on a scale of (1) A great deal to (4) None. Finally, the seventh factor, Daily Spiritual Experiences, was quantified by five items, e.g., "On a daily basis, how often do you experience the following": "A feeling of deep inner peace or harmony" and four other items. Responses were coded on a scale of (1) Often to (4) Never. Alphas ranged from .90 to .92.

Preliminary Analyses
As preliminary analyses, we investigated the differences in means between variables used in MIDUS-II and MIDUS-III. T-tests revealed that, with the large sample sizes, there were several significant mean differences of variables between MIDUS-II and MIDUS-III. In Cohen's d effect size, values are considered as small (0.2), medium (0.5), and large (0.8) when interpreting the effect size of the mean differences. In this study, there were many mean differences between MIDUS-II and MIDUS-III, but with only small effect sizes. Among the variables, only two revealed a Cohen's d effect size of over .20 (Social Actualization and Strain from Friends). As the participants aged, the mean value for Social Actualization decreased (from 12.88 to 11.68), and the mean value for Strain from Friends also decreased (from 1.83 to 1.72).

Main Analyses
First, Pearson product-moment correlation coefficients were calculated among the variables (see Table 1). Bivariate correlations between dispositional mindfulness and other psychological traits were then examined. The results were consistent across the two time points of MIDUS-II and MIDUS-III; that is, the z-scores (for comparing the magnitude of differences in correlation coefficients) were not significant (see Table 1).
Of the numerous psychological traits examined, Religiosity was identified as the strongest correlate of mindfulness. Consistent with previous research, evidence of convergent validity was observed, with moderate-sized positive correlations (r = .39 to r = .52, p < .001 for MIDUS-II; r = .42 to r = .52, p < .001 for MIDUS-III) between Mindfulness and the Religiosity sub-scales of Spirituality, Religious Identification, Private Religious Practices, Religious/Spiritual Coping, and Daily Spiritual Experience, with the exception of Religious Support (r = .25, p < .001 for MIDUS-II; r = .20, p < .001 for MIDUS-III).
Positive associations were observed between the Mindfulness scale and Overall Well-Being measures, consistent with previous findings. The Mindfulness scale was determined to be positively associated with two of the Social Well-Being measures (Social Integration and Social Contribution), as well as one measure of Psychological Well-Being (Personal Growth). The Personal Growth measure was found to be the strongest correlate of Mindfulness (r = .23, p < .001 for MIDUS-II; r = .24 for MIDUS-III, p < .001) among the six sub-factors.

Discussion
The present study aimed to clarify the convergent and divergent validity of dispositional mindfulness with health-related psychological and personality traits. The goal was to comprehensively assess the relationships between dispositional mindfulness and other well-established psychological constructs in the literature. In summary, bivariate correlations (displayed in Table 1) revealed that self-reported dispositional mindfulness was most strongly associated with the subscales of Religiosity, followed by Positive Emotionality, Well-Being, Sense of Control, Health Locus of Control (Self), and positive personality traits. Further, the Mindfulness scale was closely related to the Life Orientation sub-scale of Optimism and the Sympathy and Generativity scales but was negatively associated with Aggression and Neuroticism.
In our analyses, z-scores for comparing the size of correlations between MIDUS-II and MIDUS-III were all non-significant. Furthermore, agreement in both samples was quite high for the self-report measures of dispositional mindfulness. Specifically, the correlation results for dispositional mindfulness were relatively uniform across MIDUS-II and MIDUS-III samples, spanning almost ten years.
As expected, our results indicated that greater levels of mindful awareness were associated with a favorable outlook on life and more positive personality traits, with some correlations in the moderate to the strong range. These findings were consistent with previous research, which showed that higher levels of mindfulness were associated with greater well-being, positive affect, life satisfaction, vitality, optimism, autonomy, self-esteem, self-actualization, and competence. Furthermore, as expected, specific maladaptive orientations such as Pessimism, Aggression, Neuroticism, and Personal Constraints were negatively correlated with dispositional mindfulness.
Despite limitations in existing research on mindfulness, several key conclusions can be drawn from the consistent findings in our analyses. Our results are consistent with previous studies, which showed positive relationships with self-control, life satisfaction, agreeableness, objectivity, optimism, and pleasant affect (see Keng et al., 2011, for review). Our analyses also provide evidence that greater levels of mindful awareness correlate negatively with maladaptive functions such as aggression, neuroticism, depression, and perceived stress (see Brown & Ryan, 2003, for review). Our results are consistent with these previous findings.
Measures administered in MIDUS-II and MIDUS-III were shortened but reliable. Overall, the scale reliabilities of the measures were good, and the relationships between mindfulness and other variables were consistent with the existing literature on mindfulness. Furthermore, our study demonstrates that the relationships among the variables are highly stable over time by identifying similar relationships of dispositional mindfulness with other variables, using the two data sets spanning more than ten years. This evidence permits cross-validation of the dispositional mindfulness nomological network and reduces the likelihood of chance or sample-specific findings.
These findings should help establish mindfulness as a construct that has consistent relationships with other well-established psychological constructs. Based on our investigation of the nomological network, dispositional mindfulness is a construct that has associations with both adaptive and maladaptive psychological tendencies. It is particularly important to untangle this construct, as it has substantial implications for health-related interventions.
Research could be undertaken to further elucidate the construct of dispositional mindfulness and ultimately lead to clinical research and focused interventions for psychopathologies and maladaptive behavior. Mindfulness is an increasingly crucial theoretical concept in psychology, as it is a state of mind that can be developed and enhanced through practices such as meditation.

Limitations
Our study is not without limitations. Firstly, most measurements that assess mindfulness focus on a general tendency to be mindful in daily life. However, the mindfulness items in the MIDUS studies were presented in a religious/spiritual context, which could have influenced the responses of non-religious participants. Additionally, the Mindfulness scale used in the MIDUS studies was a shortened version of the original scale developed by Bodner and Langer (2001) specifically for MIDUS-II and III. As Zimmerman (1995) noted, components of dispositional mindfulness may not be fully captured by any single specific operationalization because they take on different forms in different samples and contexts. At the scale level, future researchers might compare different scales of mindfulness across various contexts to establish the construct validity of the existing measures.
Secondly, most mindfulness measures consist of self-report surveys, as they are typically easy to administer (Falkenstrom, 2010). The scope of this study was limited to understanding dispositional mindfulness through such self-report measures. Previous research has suggested that there may be a lack of correspondence across measurement types. While self-reports of mindfulness are useful in assessing the mechanisms and outcomes of mindfulness-based therapies, future research might benefit from comparing self-report and behavioral mindfulness via multiple methods (e.g., interview, behavioral tasks, self-reports, observations) to minimize the issue of method variance.
Thirdly, this study focused on bivariate associations among variables involving dispositional mindfulness. A construct may play various roles (i.e., endogenous, exogenous, moderator, or mediator variables) in different conceptual models. Given the large number of variables involved, we did not propose a specific model. However, our study could identify future research opportunities focusing on specific models with moderators or mediators.
Lastly, the current study was based on a nonclinical population mainly composed of middle-aged individuals residing in the United States. So, caution should be exercised in generalizing to other populations. It would be essential to assess whether convergent and discriminant validity of dispositional mindfulness is observed in a clinical sample and samples from diverse cultural backgrounds. There is also a clear need to establish the content validity of the various measures of mindfulness among novice and experienced meditators with different ethnic backgrounds.

Conclusion
Our study provides a convergent validity test of a self-report measure of dispositional mindfulness along with an examination of its discriminant validity. While there has been tremendous growth in research involving mindfulness in the past 30 years, the field of mindfulness science is still maturing. Meditation and mindfulness practice in clinical interventions have been used to promote physical health, mental health, and psychological well-being for multiple populations. The literature agrees that mindfulness practice is an essential tool in improving mental health (Brown & Ryan, 2003;Falkenstom, 2010;Keng et al., 2011). Furthermore, mindful awareness can be cultivated as an individual attribute, making it a good point of leverage for personal growth efforts and clinical interventions (Brown et al., 2007;Segal, Williams, & Teasdale, 2018).
Research on the conceptualization and operationalization of mindfulness has generated debates about the meaning, assessment, development, and cultivation of this attribute. Efforts to refine and measure primary forms of mindfulness as a trait can contribute to developing theories and establishing empirical findings. We believe our study to be among the broadest analyses to date of the nomological network of dispositional mindfulness. A nomological network is a theoretical framework that represents the basic features of a construct, its observable manifestations, and the interrelationships among them (Cronbach & Meehl, 1955). Articulating a nomological network of dispositional