Could mindfulness decrease anger, hostility ... - Wiley Online Library

AGGRESSIVE BEHAVIOR Volume 36, pages 28–44 (2010)

Could Mindfulness Decrease Anger, Hostility, and Aggression by Decreasing Rumination? Ashley Borders1, Mitch Earleywine2, and Archana Jajodia3 1

The College of New Jersey, Ewing, New Jersey University at Albany, State University of New York, Albany, New York 3 Veterans Affairs San Diego Healthcare System, University of California at San Diego, San Diego, California 2

: : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : Research suggests that rumination increases anger and aggression. Mindfulness, or present-focused and intentional awareness, may counteract rumination. Using structural equation modeling, we examined the relations between mindfulness, rumination, and aggression. In a pair of studies, we found a pattern of correlations consistent with rumination partially mediating a causal link between mindfulness and hostility, anger, and verbal aggression. The pattern was not consistent with rumination mediating the association between mindfulness and physical aggression. Although it is impossible with the current nonexperimental data to test causal mediation, these correlations support the idea that mindfulness could reduce rumination, which in turn could reduce aggression. These results suggest that longitudinal work and experimental manipulations mindfulness would be worthwhile approaches for further study of rumination and aggression. We discuss possible implications of these results. Aggr. Behav. r 2009 Wiley-Liss, Inc. 36:28–44, 2010.

: : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : Keywords: aggression; anger; hostility; rumination; mindfulness

INTRODUCTION

Recent research documents important associations between rumination, hostility, anger, and aggression. Defined as repetitive, uncontrollable thoughts about negative internal or external experiences [Ingram, 1990; Martin and Tesser, 1996], rumination involves harping on something negative, seemingly without end or control. These repetitive thoughts often focus on current feelings, related causes, consequences, and potential solutions [Lyubomirsky and Nolen-Hoeksema, 1995]. For instance, individuals might become fixated on thoughts about why they cannot cope with things, why their partners treated them badly, or how they will perform in an upcoming speech. We will first briefly review the evidence suggesting that rumination exacerbates and leads to anger, hostility, and aggression. We will then turn to a discussion of how mindfulness may counteract the effects of rumination. Rumination and Aggression-Related Variables Nonexperimental and experimental studies alike have found robust links between rumination, anger, hostility, and aggression. Examining the influence of r 2009 Wiley-Liss, Inc.

trait rumination, for instance, Collins and Bell [1997] randomly assigned low ruminators and high ruminators to provocation (negative feedback about performance) or control conditions. Participants then competed with an ‘‘opponent’’ and could choose to increase their own points, deduct points from their opponent, or deliver a loud white noise to the opponent. High ruminators in the provocation condition exhibited more aggression (e.g., total number of noise blasts) than low ruminators in the same condition. Similarly, Caprara [1986] and Caprara et al. [1987] found that high dispositional ruminators exhibited more hostility, deliberated more over thoughts of retaliation, and delivered stronger shocks following hostile experiences than did low ruminators. Hostile rumination also longitudinally predicts self-reported aggressive and delinquent behavior in adolescents [Caprara et al., 2007]. Correspondence to: Ashley Borders, The College of New Jersey, Social Sciences Building 121, 2000 Pennington Rd., Ewing 08628, New Jersey. E-mail: [email protected]

Received 5 October 2008; Accepted 20 July 2009 Published online 22 October 2009 in Wiley InterScience (www. interscience.wiley.com). DOI: 10.1002/ab.20327

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In addition, measures of rumination correlate with increased vengefulness, or the disposition to seek revenge after suffering an interpersonal offense [Barber et al., 2005; McCullough et al., 1998, 2001]. Experimental manipulations of rumination show similar links to anger and aggression. Bushman [2002] instructed participants to hit a punching bag as many times as they wanted (venting) and at the same time to think about a partner who criticized their work (rumination). By contrast, participants in the distraction condition focused their thoughts on becoming physically fit while they hit the punching bag, and participants in the control condition sat quietly for several minutes. Results indicated that rumination while venting increased subsequent selfreported anger and aggressive behavior (again in the form of delivered noise blasts). Rusting and NolenHoeksema [1998] manipulated rumination by asking angered participants to focus their attention on thoughts that were emotion- and self-focused but not explicitly about anger (e.g., ‘‘why people treat you the way they do’’). In the distraction condition, participants focused their attention on nonemotional thoughts (e.g., ‘‘the layout of the local post office’’). Following these manipulations, participants completed stories that were later rated for anger content. In all experiments, rumination increased anger, whereas distraction decreased or had no effect on pre-existing anger. Researchers have also investigated the impact of rumination on triggered displaced aggression, or instances in which a person who is provoked but cannot retaliate directly against the source of provocation subsequently becomes aggressive with a person who merely provides a trivial annoyance [Pedersen et al., 2000]. In two studies [Bushman et al., 2005], provoked participants who ruminated were more aggressive after a trivial triggering event than were those in a distraction condition. Rumination did not increase aggression in the absence of a trigger. Finally, provocation-induced negative affect correlated with aggression only for participants in the rumination condition. In sum, research suggests that rumination exacerbates angry mood, increases hostility, interacts with perceived provocation to elicit more aggressive behaviors, and may increase physiological arousal. The processes by which rumination causes aggression are still being explored. Network models propose that mood-congruent information is organized in long-term memory around central nodes [Berkowitz, 1990; Bower, 1981]. These associative networks link related memories, thoughts, feelings, and behavioral tendencies. Activation of one part of

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an associative network (e.g., a particular negative emotion) can activate other items stored in that network. Miller et al. [2003] suggested that repetitive thoughts and elaborations about a provocation may maintain the activation of anger-related associative networks over time, making angry mood and hostile thoughts more accessible and subsequent aggressive behavior more likely. Some evidence now supports this theory. Angered participants made to ruminate became angrier and exhibited more aggressive responses following a minor trigger than did participants who distracted themselves [Bushman et al., 2005; Rusting and Nolen-Hoeksema, 1998]. Thus, rumination about perceived insults may activate aggressive associative networks, exacerbating existing angry mood and hostile cognitions and resulting in aggressive behavior. Moreover, these results reinforce the idea that anger, hostility, and aggression are unique constructs that can influence each other [e.g., Bryant and Smith, 2001] and should therefore be examined separately. The above discussion strongly implies that counteracting rumination might decrease aggression, anger, and hostility. Research suggests that the active components of rumination are out-of-control repetitive thoughts [Segerstrom et al., 2003] and negative judgments about current distress [Rude et al., 2007]. Moreover, Martin and Tesser [1996] theorized that rumination can be either about past events or future concerns. Several researchers have recently theorized that mindfulness may constitute a potential antidote to this kind of thought process. Mindfulness and its Impact Extensive research suggests that mindfulness is associated with a range of positive outcomes, from improved life satisfaction and positive mood to decreased stress [Brown and Ryan, 2003; Shapiro et al., 2008]. Clinically, mindfulness interventions have effectively treated depression, anxiety, eating disorders, substance abuse, and borderline personality disorder [for reviews, see Baer, 2003; Grossman et al., 2004]. Only recently studies have examined the mechanisms of mindfulness and its association with rumination and aggression. In this section, we will first discuss the concept of mindfulness and then differentiate it from rumination and related thought processes. We will also review the brief literature examining associations between mindfulness and aggression-related variables. Born out of traditional Eastern meditation practices, mindfulness involves a unique way of paying attention [Baer, 2003; Shapiro et al., 2006]. First, it Aggr. Behav.

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involves bringing one’s full attention to the present moment, rather than dwelling on past events or future possibilities. In fact, mindfulness may be seen in part as a form of attention regulation, in that individuals who are mindful are able to consciously redirect their attention away from past negative memories or future worries and back to present sensations [Baer, 2003; Bishop et al., 2004]. Mindfulness is also characterized by an attitude of nonjudgmental acceptance [Shapiro et al., 2006, 2008]. People practicing mindfulness can notice and experience current internal and external events in an accepting way. Teasdale et al. [1995, 2003] argue that this acceptance permits people to stop brooding about their unpleasant thoughts and feelings. Rather than labeling pain as ‘‘bad’’ and something to avoid, mindful people view pain as just one of many sensations to experience. Hayes et al. [1999] suggests that individuals who are mindful are more willing to experience negative internal and external events. In one study, participants engaged in mindful breathing showed a greater willingness to view pictures with negative emotional content [Arch and Craske, 2006]. Thompson and Waltz [2008] also found links between mindfulness and experiential avoidance. Mindful individuals were less likely to view negative feelings and unpleasant events as scary or unacceptable. This attitude of equanimity toward all kinds of emotions and thoughts may decrease people’s perceived need for rumination, as current distress is not judged so negatively. Distinguishing Between Mindfulness, Rumination, and Related Constructs The intentional ‘‘here and now’’ focus of attention contrasts with the seemingly uncontrollable mental circles people experience when they are ruminating. Some researchers have in fact conceptualized rumination as maladaptive self-focus [Ingram, 1990; Mor and Winquist, 2002], a process characterized by internal, sustained, and rigid attention to perceived discrepancies between current and desired states. This rigid and repetitive self-focus elicits negative affect, particularly when a negative discrepancy exists and when one fails to resolve such a discrepancy [Carver and Scheier, 1981]. By contrast, mindfulness is thought to be characterized by cognitive flexibility, so that it allows people to disengage from rigid mental cycles [Bishop et al., 2004; Shapiro et al., 2006]. Mindful people may notice negative affect in one moment but will inevitably notice other sensations or events in subsequent moments, so they do not get swept up Aggr. Behav.

in analyzing negative feelings. Because there is so much to observe in any given moment, this intentional attention to the present moment [Shapiro et al., 2006] necessitates flexibility and prevents rigid self-absorption. In support of this theory, mindfulness is associated with increased cognitive flexibility [Davis and Nolen-Hoeksema, 2000], whereas rumination is associated with decreased flexibility on neuropsychological tests of executive functioning [Philippot and Brutoux, 2007]. Thus, the intentional and flexible present-focus of mindfulness contrasts sharply with the more rigid dwelling in the past or future that characterizes rumination. Research provides support for the negative associations between mindfulness and rumination. Brown and Ryan [2003] found that their mindfulness measure correlated negatively with rumination. Coffey and Hartman [2008] found a pattern of correlations suggesting that rumination might mediate the association between mindfulness and psychological distress (as measured by a latent factor combining depressive and anxious symptoms). Recent experiments have examined the effect of mindfulness meditation by novice meditators on rumination. Chambers et al. [2008] had 20 participants engaged in a 10-day intensive mindfulness meditation retreat. Compared with a control group that did not attend the retreat, these participants reported decreased depressive symptoms and reflective rumination. Similarly, two studies [Ramel et al., 2004; Shapiro et al., 2008] found that people who participated in 8-week mindfulness courses showed decreased rumination. Moreover, a change in reported rumination accounted for decreases in depressive and anxious symptoms [Ramel et al., 2004]. In sum, initial evidence suggests that heightened mindfulness can decrease rumination, which in turn results in less depression and anxiety. Thus, decreased rumination appears to be one of the mechanisms by which mindfulness leads to greater well-being and less suffering. Theory and initial research suggest that mindfulness is a separate construct from distraction, which has traditionally been seen as a form of avoidant coping [Sexton and Dugas, 2008] and is a common alternative to rumination manipulations [Bushman, 2002; Rusting and Nolen-Hoeksema, 1998]. Distraction is a coping skill that involves pushing away unpleasant thoughts and feelings, often by focusing on other thoughts or activities. Although moderate forms of distraction (such as focusing on pleasant events or neutral thoughts) may be beneficial [Morrow and Nolen-Hoeksema, 1990; Nolen-Hoeksema et al., 1993], this strategy

Mindfulness and Rumination

only works for a short time and under certain conditions [Hamilton and Ingram, 2001]. Moreover, attempting to push specific thoughts and feelings out of awareness can paradoxically increase the frequency of negative cognitions and produce greater emotional reactions [Wegner and Zanakos, 1994; Wenzlaff and Wegner, 2000]. Mindfulness, by contrast, constitutes an alternative to distraction. Present-centered awareness should in fact engender a deeper experience of one’s thoughts and emotions [Shapiro et al., 2006], rather than avoidance. Baer [2003] suggests that mindfulness might function in part by exposing individuals to their pain, resulting in subsequent desensitization and decreased negative reactions to pain. Other researchers suggest that mindfulness changes one’s relationship to thoughts rather than changing the content of thought [Hayes et al., 1999]. Unlike distraction, which temporarily pushes away unpleasant cognitions or replaces them with other thoughts, mindfulness should foster the ability to fully experience negative feelings and thoughts without being as emotionally upset by them. Thus, even though experimental distraction manipulations can decrease negative affect and aggression [Bushman, 2002; Rusting and NolenHoeksema, 1998], mindfulness may provide a better alternative. Broderick [2005] provided some initial support for this hypothesis. Comparing 8-minute rumination and distraction inductions to 8 minutes of mindfulness meditation, they found that rumination exacerbated sad mood, whereas distraction and mindfulness meditation decreased sad mood. Importantly, however, mindfulness meditation resulted in less sad mood than did distraction. Mindfulness therefore appears to be a different construct than distraction and may have greater potential as an alternative to ruminative thought processes. Another interesting question is whether mindfulness or rumination, or both, are associated with increased self-awareness. Self-awareness generally decreases physical and verbal aggression [Kinney et al., 2001; Prentice-Dunn and Rogers, 1982; Scheier et al., 1974]. These studies typically induced self-awareness by having participants look at themselves in the mirror, take a self-esteem measure, or focus primarily on themselves rather than others. Carver [1975] suggested that self-awareness makes people more aware of their internal rules about aggression, thus preventing the deindividuation that might allow for aggressive actions that violate social norms [see also Prentice-Dunn and Rogers, 1982]. Interestingly, rumination may not be associated with self-awareness. Trapnell and Campbell [1999] found that rumination correlated with self-reflection

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(‘‘I’m trying to figure myself out’’) but not with awareness of internal states (‘‘I’m generally attentive to my inner feelings’’), as measured by the Private Self-Consciousness scale [Fenigstein et al., 1975]. By contrast, mindfulness is associated with greater awareness of internal states but not with increased self-reflection [Brown and Ryan, 2003]. Moreover, mindfulness correlated with increased attention to and clarity of feelings, as well as value-concordant behavior [Brown and Ryan, 2003]. Thus, although rumination involves repetitive and rigid thoughts about negative thoughts and emotions, it is not apparently associated with greater self-awareness. Mindfulness, by contrast, does appear to foster more self-awareness of internal states and personal values. As such, it should theoretically be associated with less aggression. Mindfulness and Aggression Mindfulness covaries with aggression-related variables. Using their self-report measure of mindfulness, Brown and Ryan [2003] found that greater mindfulness was associated with less impulsiveness and hostility. Heppner et al. [2008] likewise found that greater mindfulness correlated with less anger, hostility, and verbal aggression. In a second study, they had some participants engaged in a mindful eating exercise before receiving a social rejection. Participants in the mindful condition showed less subsequent aggression than did participants who only received a rejection but did not engage in the mindfulness exercise. In a pair of multiple baseline studies, Singh et al. [2007a,b] had three adults with mental illness and three adolescents with conduct disorder participate in a 4-week course in mindfulness training. They were then asked to continue their mindfulness practice on their own. Incidents of aggressive and delinquent behavior were recorded for at least 25 weeks. For all participants, aggression decreased or was eliminated. Although these results are promising, no data have been collected on the mechanisms by which mindfulness decreases aggressive behavior. The above discussion strongly suggests that rumination may be one such mechanism. The Current Studies In sum, although previous research suggests that mindfulness decreases rumination and that mindfulness may decrease aggression, anger, and hostility, no studies have examined the relationships among all of these variables. We conducted two survey studies to examine whether rumination might be one mechanism by which mindfulness is Aggr. Behav.

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associated with less aggression, anger, and hostility. Although nonexperimental research cannot prove a causal mediational model, we expected to find a pattern of correlations consistent with rumination mediating the association between mindfulness and these aggression-related variables. These results would provide an encouraging first step toward establishing a rumination-mediated link between mindfulness and aggression.

STUDY 1

Our first study examined the associations between mindfulness, rumination, and four aggression-related variables in an undergraduate sample. Specifically, we examined the subscales of the Aggression Questionnaire (AQ) [Buss and Perry, 1992] separately to yield indices of physical aggression, verbal aggression, anger, and hostility. Given previous studies [Brown and Ryan, 2003; Heppner et al., 2008], we expected that mindfulness would be strongly associated with hostility, anger, and verbal aggression. Although one previous study failed to find significant correlations between mindfulness and physical aggression using the BPAQ [Heppner et al., 2008], mindfulness-based training has been shown to reduce physical aggression [Singh et al., 2007a,b]. Thus, we had no clear hypothesis about the link between mindfulness and physical aggression. We also used the Rumination and Reflection Scale [Trapnell and Campbell, 1999], which was designed to differentiate between two types of private selfconsciousness [Fenigstein et al., 1975]. Reflection taps both self-reflection and awareness of internal states and is related to openness to experience and need for cognition [Trapnell and Campbell, 1999]. Rumination taps only self-reflection and is associated with neuroticism, anxiety, depression, and negative affect. We used this measure because it allowed us to compare the associations between the two subscales and other study variables. Consistent with prior work [Brown and Ryan, 2003], we expected mindfulness to correlate with rumination but not with reflection. Therefore, comparing the rumination and reflection subscales allowed us to further establish the construct validity of mindfulness. We also selected this measure because it constitutes a general measure of rumination, rather than symptom-specific rumination. There are several measures of anger-related rumination. Caprara [1986] created a measure of ‘‘dissipation–rumination,’’ or the storing in memory of various experiences of provocation, expectations, judgments, and Aggr. Behav.

thoughts of retaliation. More recently, Sukhodolsky et al. [2001] created a measure specifically about ‘‘anger rumination,’’ which assesses memories of past anger experiences, attention to immediate anger experiences, and thoughts about the antecedents and consequences of an anger experience. Unfortunately, these anger-rumination measures confound process with outcome. We would expect more shared variance between anger-rumination measures and aggression than between general measures of rumination and aggression. Therefore, the strongest evidence for the links between rumination and aggression-related variables will come from studies that use measures of general rumination. Given the impressive existing literature, we expected rumination to correlate positively with all four aggression subscales. Method Participants and procedure. We collected data from 464 undergraduate students at a major university in Los Angeles. They completed these three measures as part of a larger questionnaire given to students enrolled in psychology courses. From information reported on the larger questionnaire packet, two-thirds of the undergraduate participants were female. Just over 50% of participants were Caucasian-American, 19% were AsianAmerican, 9% were Hispanic-American, 7% were African-American, and 13% rated themselves as ‘‘other.’’ Participants’ mean age was 19.7. All responses were anonymous and informed consent was obtained before completing the questionnaire packet. Measures Mindfulness. We measured trait mindfulness using the Mindful Attention Awareness Scale [MAAS; Brown and Ryan, 2003]. This 15-item questionnaire inquires about participants’ typical level of present awareness and attention (e.g., ‘‘I rush through activities without being really attentive to them’’ and ‘‘I drive places on ‘automatic pilot’ and then wonder why I went there’’). Participants indicate how often they have these experiences on a 6-point Likert scale from ‘‘almost always’’ to ‘‘almost never.’’ Higher scores reflect more mindfulness. Brown and Ryan [2003] showed that the MAAS correlates with other mindfulness scales, as well as with emotional intelligence, openness to experience, and internal state awareness. The MAAS also reliably distinguished between meditation practitioners and control participants [Brown and Ryan, 2003]. One item from the MAAS (‘‘I find

Mindfulness and Rumination

myself preoccupied with the future or the past’’) seemed to overlap conceptually with the rumination construct. This item also showed low factor loadings during measure construction [l 5 .28, Brown and Ryan, 2003]. Therefore, this item was left out of our analyses. The other 14 items were used to create a latent variable of mindfulness (see below). Internal consistency of these 14 items was good, a 5 .86. Rumination. Participants completed the Rumination and Reflection Questionnaire [Trapnell and Campbell, 1999]. This 24-item measure assesses both rumination (e.g., ‘‘I always seem to be rehashing in my mind recent things I’ve said or done’’) and reflection (e.g., ‘‘I love exploring my ‘inner self’’). Participants indicate their level of agreement with each item on a 5-point Likert scale from ‘‘strongly disagree’’ to ‘‘strongly agree.’’ Higher subscale scores indicate more rumination and reflection. Trapnell and Campbell [1999] found that the rumination subscale correlated highly with neuroticism, whereas the reflection subscale correlated with measures of openness to experience and need for cognition. The rumination and reflection subscales were minimally but significantly correlated in this sample, r 5 .18, Po.05. These results accord with small correlations found by the Trapnell and Campbell [1999], suggesting that these subscales measure independent tendencies. Moreover, the reflection subscale did not correlate significantly with mindfulness or any aggression subscale.1 Thus, only the 12 rumination items were used in testing the measurement and mediational models (see below). Internal consistency of this measure was also good in this sample, a 5 .90. Aggression, anger, and hostility. Finally, participants completed the AQ [Buss and Perry, 1992]. This 29-item measure assesses physical aggression, verbal aggression, hostility, and anger. Participants indicate how much each item describes them on a 5-point Likert scale from ‘‘extremely uncharacteristic of me’’ to ‘‘extremely characteristic of me.’’ Higher scores reflect more aggression. This measure reliably differentiates between violent and nonviolent participants and correlates with responses to provoking scenarios, peer reports of aggression, and other self-reports of aggression [Harris, 1997; 1 We initially tested a measurement model that included the reflection subscale, as well as rumination, mindfulness, and the four aggression variables. Allowing these seven factors to intercorrelate, the model fit the data well, w2 (1154) 5 1845.53, CFI 5 .85, RMSEA 5 .051. The 12 reflection items all had high loadings (ls from .58 to .78). However, the reflection scale showed small and nonsignificant correlations with all factors (r’so.10) other than rumination (r 5 .18, Po.05).

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Morren and Meesters, 2002; O’Connor et al., 2001]. Although some research confirms the original factor structure of this measure [e.g., Harris, 1995], other results suggest that the original 29 items do not load sufficiently onto four factors, especially across different populations [Bryant and Smith, 2001; Vigil-Colet et al., 2005; Williams et al., 1996]. Bryant and Smith [2001] proposed a reduced version of the AQ that maintains the four original factors but includes only the three items with the highest loadings on each factor. They found that across five diverse samples, this 12-item AQ fit the data better than the original 29-item measure. Therefore, we used only three items to create each of the four latent variables of physical aggression (‘‘Given enough provocation, I may hit another person,’’ ‘‘There are people who pushed me so far that we came to blows,’’ ‘‘I have threatened people I know’’), verbal aggression (‘‘I often find myself disagreeing with people,’’ ‘‘I can’t help getting into arguments when people disagree with me,’’ ‘‘My friends say that I’m somewhat argumentative’’), anger (‘‘I flare up quickly but get over it quickly,’’ ‘‘Sometimes I fly off the handle for no good reason,’’ ‘‘I have trouble controlling my temper’’), and hostility (‘‘At times I feel I have gotten a raw deal out of life,’’ ‘‘Other people always seem to get the breaks,’’ ‘‘I wonder why sometimes I feel so bitter about things’’). Internal consistency values for these items of physical aggression (a 5 .72), verbal aggression (a 5 .78), hostility (a 5 .75), and anger (a 5 .70) were adequate. Plan of Analyses Structural equation modeling (SEM) was used to test whether it is plausible that rumination could mediate the association between mindfulness and aggression. We used the MPlus program 5.0 [Muthe´n and Muthe´n, 1998–2007] with the missing at random assumption [Little and Rubin, 1987] and maximum likelihood estimation. We first tested a measurement model to confirm the relations of the observed variables with their latent constructs [Anderson and Gerbing, 1988]. Based on CFAs done during construction of the MAAS [Brown and Ryan, 2003] and the RRS [Trapnell and Campbell, 1999] and the high Cronbach’s as obtained in these samples, we tested single-factor models for the mindfulness and rumination items. Based on Bryant and Smith’s [2001] findings, we tested a four-factor (physical aggression, verbal aggression, hostility, anger) model of the refined 12-item AQ. The measurement model Aggr. Behav.

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allowed these six latent variables to intercorrelate freely. To better confirm this measurement model, we compared the above six-factor model to several alternative models: (a) a five-factor model in which the mindfulness and rumination items loaded onto a single factor, (b) a three-factor model in which all 12 aggression items loaded onto a single factor, (c) a two-factor model in which the mindfulness and rumination items loaded onto one factor and all aggression items loaded onto one factor, and (d) a single-factor model with all measured variables loading onto one factor. w2 difference tests compared each alternative model to the proposed sixfactor model. In these tests, if the difference in w2 was significant for the number of degrees of freedom difference, then the model fit significantly less well than the proposed model. We next used path models to test the plausibility of mediation from trait mindfulness to the four aggression factors via rumination. First, we fit a model where the aggression subscales were regressed on trait mindfulness (see Fig. 1A). We then introduced the rumination factor as a mediator (see Fig. 1B). We looked for evidence suggesting mediation in a few ways. Traditionally, a test of mediation requires three separate regression analyses [Baron and Kenny, 1986]. First, the independent variable (IV; mindfulness) must predict the dependent variable (DV; aggression). This first analysis establishes that a relationship in fact exists to be explained. Second, the IV must predict the proposed mediator (rumination). Third, the DV is regressed on both the IV and the mediator. The mediator must predict the DV, even with the IV also entered into the equation. If these three tests are all significant, then the coefficient for the IV in this third equation is examined. Statistically, mediation occurs when the IV no longer affects the DV after inclusion of the mediator in the regression equation. Conceptually, this result suggests that the original effect of the IV is in fact explained by the mediating variable. In other words, the IV has no direct effect on the DV, after accounting for the effect of the mediator. True tests of mediation require experimental or longitudinal designs in order to demonstrate that the IV in fact causes the mediator, which in turn causes the DV. Nonexperimental studies like this one cannot determine the actual temporal association between variables. Rather, statistical tests of mediation with these data suggest that the proposed mediation model is plausible. Researchers have designed ways to quantify the effect of mediation and subsequently test for Aggr. Behav.

significance [for a review, see MacKinnon et al., 2002]. One common approach is to create an estimate of the ‘‘indirect effect,’’ or the effect of the mediator [e.g., Sobel, 1982]. The indirect effect is defined as a product of two regression coefficients: (1) the effect of the IV on the mediator and (2) the effect of the mediator on the DV after controlling for the IV. A significance test of mediation roughly determines whether the indirect effect differs significantly from zero. Traditional significance tests involve dividing the indirect effect by an estimate of its standard error and comparing the resulting value to the standard normal distribution [see MacKinnon et al., 2002; e.g., Sobel, 1982]. However, analyses indicate that estimates of indirect effects are not necessarily normally distributed [Bollen and Stine, 1990; MacKinnon et al., 2002]. Accordingly, these traditional tests generally have low power and may lead to incorrect conclusions. One promising new method of testing indirect effects without making assumptions about normality uses bootstrapping methodology [Bollen and Stine, 1990; MacKinnon et al., 2004; Preacher and Hayes, 2004]. A ‘‘bootstrap sample’’ consists of N individuals sampled randomly with replacement from the original data set, where N is the size of the original data set. Five hundred bootstrap samples are created in this way, yielding an empirical sampling distribution from which 95% confidence intervals can be estimated [Bollen and Stine, 1990; MacKinnon et al., 2004]. In simulations in which the distributions of indirect effects are skewed, these resampling methods have more power than traditional tests that assume normality [Bollen and Stine, 1990; MacKinnon et al., 2004; Shrout and Bolger, 2002]. Recent simulation studies suggest that the bias-corrected bootstrap method produces the most accurate confidence intervals and has greater power and more accurate Type I error rates than other bootstrap methods [Cheung and Lau, 2008; MacKinnon et al., 2004]. Therefore, our analyses below report both the indirect effects of mediation as well as bias-corrected bootstrap confidence intervals.

Results and Discussion Measurement model. A measurement model was used to confirm the factor structures of trait mindfulness, rumination, and the four [shortened; Bryant and Smith, 2001] aggression subscales. The model fit the data well, w2(650) 5 1388.60, CFI 5 .89, RMSEA 5 .049.

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Fig. 1. (A) Path model with mindfulness predicting aggression variables and (B) mediation model with rumination mediating the association between mindfulness and the aggression variables.

As expected, the model confirmed a single latent factor structure for trait mindfulness. The factor loadings for the individual mindfulness items ranged from .30 to .78. Items like ‘‘I could be experiencing some emotion and not be conscious of it until some time later’’ and ‘‘I tend not to notice feelings of physical tension or discomfort until they really grab my attention’’ had the lowest factor loadings. Items like ‘‘It seems I am running on automatic, without much awareness of what I’m doing’’ and ‘‘I find myself doing things without paying attention’’ had

the highest factor loadings. These results are in accordance with earlier factor analyses of this measure [Brown and Ryan, 2003]. We computed a composite reliability coefficient by the method suggested by Werts et al. [1974] using the factor loadings of individual items and residual variances [see also Lattin et al., 2003]. The measure showed good composite reliability, rc 5 .86. The model also confirmed a single latent factor structure for rumination. The factor loadings for the individual rumination items were high, ranging from Aggr. Behav.

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.51 to .77. The composite reliability for this measure in this sample was .90. The model confirmed a four-factor model of aggression, using only 12 items from the AQ. Factor loadings and composite reliabilities were good for physical aggression (ls from .59–.73, rc 5 .73), verbal aggression (ls from .71–.77, rc 5 .78), anger (ls from .49–.79, rc 5 .71), and hostility (ls from .69–.76, rc 5 .76). To better confirm this measurement model, we compared the above six-factor model to several alternative models. Table I shows model fits for all of these models. A w2 difference test revealed that the six-factor model provided a significantly better fit than combining rumination and mindfulness into a single factor, supporting the discriminant validity of rumination and mindfulness as distinct constructs. Combining the aggression factors into a single factor also created a significantly worse fit, confirming previous work on the discriminant validity of these separate facets of aggression. The six-factor model also fit significantly better than treating a two-factor model of rumination/mindfulness and aggression. In addition, a single-factor model fit significantly less well than the proposed six-factor model, revealing that the distinctions among these constructs account for more data than a single factor of self-report. Thus, theoretically tenable alternative models fit the data less well than the proposed six-factor model. Table II shows variable means, standard deviations, and ranges. Participants on average endorsed a moderate level of trait rumination and trait mindfulness. Participants in this sample also reported moderate levels of verbal aggression, hostility, and anger, but they reported lower levels of physical aggression.

Table III presents intercorrelations between all study variables. Rumination and trait mindfulness showed a strong negative correlation. The more mindful people were, the less they ruminated. Higher mindfulness was related to less aggression on all aggression subscales. Rumination showed strong positive correlations with the anger and hostility subscales and weaker or nonsignificant associations with physical (r 5 .08, ns) and verbal aggression (r 5 .12, Po.05). Finally, the aggression subscales showed strong positive intercorrelations, as expected [Bryant and Smith, 2001; Buss and Perry, 1992]. Mediation models. A path model with the aggression subscales regressed on trait mindfulness was fitted first. This model fit the data adequately, w2(289) 5 610.19, Po.001, RMSEA 5 .049, CFI 5 .91. Trait mindfulness was a significant predictor of all four aggression subscales (see Table IV). Next, we added rumination as a mediator variable. The model fit was adequate, w2(650) 5 1388.59, Po.001, RMSEA 5 .049, CFI 5 .89. Trait mindfulness significantly predicted rumination, b 5 .46, SE 5 .04, Po.001. Table IV shows all TABLE II. Means, Standard Deviations, and Ranges for All Study Variables Study 1 Variable Mindfulness Rumination Physical aggression Verbal aggression Hostility Anger

Study 2

Mean

SD

Range

Mean

SD

Range

4.05 3.55 1.81 2.54 2.54 2.21

.76 .71 .92 .94 .98 .85

1.2–5.8 1.4–5 1–5 1–5 1–5 1–5

4.09 3.19 1.39 2.42 2.03 2.06

.70 .83 .66 .83 1.03 .85

2.2–5.9 1.2–5 1–4.3 1–4.7 1–5 1–4.7

TABLE I. Alternative Models to the Proposed six-factor Measurement Model Model tested Study 1 Proposed six-factor model: mindfulness factor, rumination factor, four aggression factors Five-factor model: one rumination/mindfulness factor, four aggression factors Three-factor model: rumination factor, mindfulness factor, one aggression factor Two-factor model: one rumination/mindfulness factor, one aggression factor One-factor model: single rumination/mindfulness/aggression factor Study 2 Proposed six-factor model: mindfulness factor, rumination factor, four aggression factors Five-factor model: one rumination/mindfulness factor, four aggression factors Three-factor model: rumination factor, mindfulness factor, one aggression factor Two-factor model: one rumination/mindfulness factor, one aggression factor One-factor model: single rumination/mindfulness/aggression factor Po.05; Po.01.

Aggr. Behav.

w2 (df)

RMSEA

CFI

Dw2 (Ddf)

1388.60 2553.89 1973.57 3131.88 3803.67

(650) (655) (662) (664) (665)

.049 .079 .065 .089 .101

.89 .71 .80 .62 .52

– 1165.29 (5) 584.97 (12) 1743.28 (14) 2415.07 (15)

1069.17 1573.89 1317.37 1819.33 2014.74

(650) (655) (662) (664) (665)

.059 .087 .073 .097 .105

.87 .71 .79 .64 .58

– 504.72 (5) 248.20 (12) 750.16 (14) 945.57 (15)

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TABLE III. Zero-Order Correlations for All Study Variables Variable 1. 2. 3. 4. 5. 6.

Mindfulness Rumination Physical aggression Verbal aggression Hostility Anger

1 – .46 .14 .22 .38 .37

2

3

.48 – .08 .12 .56 .28

4

.24 .22

.25 .36 .36

– .46 .35 .51

– .30 .62

5

6

.43 .63 .40 .40

.23 .43 .48 .59 .50 –

– .52

Values below the diagonal are from Study 1. Values above the diagonal are from Study 2. Po.05; Po.01; Po.001.

TABLE IV. Betas, Standard Errors, Indirect Path Estimates, and Bias-Corrected Bootstrap CIs for Mediational Models Model tested Study 1 Mindfulness to aggression (SE) Rumination to aggression (SE) Mindfulness to aggression, via rumination (SE) Indirect paths (SE) Bias-corrected bootstrap 95% confidence intervals Study 2 Mindfulness to aggression (SE) Rumination to aggression (SE) Mindfulness to aggression, via rumination (SE) Indirect paths (SE) Bias-corrected bootstrap 95% confidence intervals a

PA b (SE)

VA b (SE)

Hostility b (SE)

Anger b (SE)

.14 (.06) .02 (.06) .13 (.06) .01 (.03) ( .18, .16)

.22 (.05) .02 (.06) .21 (.06) .01 (.03) ( .16, 11)

.38 (.05) .48 (.05) .16 (.06) .22 (.03)a ( .91, .38)

.37 (.05) .14 (.06) .31 (.06) .06 (.03)a ( .22, .01)

.21 (.09) .05 (.10) .19 (.10) .02 (.05) ( .23, .11)

.24 (.09) .33 (.10) .08 (.10) .15 (.05)a ( .51, .08)

.41 (.08) .54 (.08) .16 (.08) .25 (.05)a ( 1.13, .57)

.23 (.08) .41 (.09) .03 (.10) .19 (.05)a ( .67, .11)

Zero is not included in the 95% confidence interval, indicating that the indirect path is significantly different from zero.

Po.05; Po.01; Po.001.

other betas in the mediational model. Mindfulness still significantly predicted all aggression subscales. Rumination only significantly predicted hostility and anger. To look for whether the pattern of relations was consistent with a mediating role for rumination, we first examined whether the bs between mindfulness and the aggression subscales decreased with the inclusion of rumination in the model. The b estimates for the links between mindfulness and hostility dropped from .38 to .16 with the inclusion of rumination, consistent with partial mediation. Likewise, the bs between mindfulness and anger dropped from .37 to .31. The bs from mindfulness to physical and verbal aggression barely changed with the inclusion of rumination (for both, bs dropped from .02 to .01), indicating that rumination did not account for these associations. We also calculated indirect effect estimates and biascorrected bootstrap estimates for the 95% confidence intervals (see Table IV). Confidence intervals that do not include zero indicate a significant indirect effect. Only the indirect effects for hostility and anger were meaningfully different from zero. These results suggest that our proposed mediation model is plausible and that rumination may partially

mediate the associations between mindfulness and anger and hostility. In sum, Study 1 found support for many of our hypotheses. Specifically, greater mindfulness was associated with less rumination. Mindfulness was also negatively associated with all four aggression subscales. Finally, the pattern of correlations was consistent with rumination partially mediating the links between mindfulness and both hostility and anger. Thus, it appears that more mindful people may be less angry and hostile in part because they ruminate less. This finding constitutes the first evidence that rumination may be one potential mechanism by which mindfulness is associated with anger and hostility. The absence of meaningful associations between rumination and physical and verbal aggression was surprising, given previous evidence that rumination produces increased behavioral aggression [Bushman, 2002; Bushman et al., 2005; Caprara et al., 1987]. The absence of an observed association between rumination and aggression could have resulted from low levels of particularly physical aggression reported in this undergraduate sample. The presence of a floor effect would make any existing relationships difficult to find. Replication with a different Aggr. Behav.

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population would help clarify the association between rumination and behavioral aggression. Moreover, because we did not have access to demographic data with this sample, we were unable to determine whether the associations between mindfulness, rumination, and aggression reflected any effects of age or gender. We addressed these limitations in our second study.

regular meditation practices. Of the participants who meditated regularly, 7% meditated a few times a month, 45% meditated a few times a week to once a week, and 48% meditated once a day or more. We included the same measures of mindfulness, rumination, and aggression as in Study 1.

Results and Discussion STUDY 2

Study 2 was a replication study using a nonundergraduate population. The vast majority of research on links between rumination and aggression has employed undergraduate samples. Finding similar results in a different population will help generalize these important associations to people of different ages and life experiences. Moreover, we wanted to find a sample with increased exposure to and knowledge about mindfulness. Grossman [2008] suggests that because of their general inexperience with mindfulness and related concepts, undergraduates’ understanding of and subsequent reporting of ‘‘mindfulness’’ likely differs from the construct that authors of these measures intended. Therefore, we targeted adults who were presumably more knowledgeable about the construct of mindfulness, as evidenced by their membership in mindfulnessrelated listservs. The meaning of mindfulness in this population should be more in line with the conceptual basis of mindfulness measures. Method Participants and procedure. To find participants, we created an Internet survey and posted the survey link on several mindfulness-related listservs. People were invited to participate through an introductory email. Because of this method of recruitment, we cannot know what percentage of people responded to our request. All participants had to read and agree to an informed consent before participation. Study 2 had 211 participants from 26 different states and 6 countries. The participants ranged in age from 15 to 72 (mean 5 31.8, SD 5 11.8), and 60% were female. On average, these participants had graduated from college and taken some graduate courses and earned an average annual income of $40,000–60,000. Over 80% of these participants were Caucasian-American, 3% were Hispanic-American, and 5% each were AsianAmerican, African-American, and mixed. In this sample, 57% of participants reported meditating at least once in their lives, and 22% currently had Aggr. Behav.

Measurement models. Measurement models were again used to confirm the factor structure of the mindfulness, rumination, and aggression variables.2 The measurement model with trait mindfulness, rumination, and aggression fit adequately, w2(650) 5 1069.17, CFI 5 .87, RMSEA 5 .059. The factor loadings for the individual trait mindfulness items again showed a wide range (from .25 to .82) and a similar pattern as in Study 1. The factor loadings for the rumination items ranged from .62 to .86. Aggression items loaded onto their subscales similarly to Study 1 (ls from .43 to .90). The composite reliabilities for trait mindfulness (rc 5 .87) and rumination (rc 5 .94) were good. The composite reliabilities for physical aggression (.74), verbal aggression (.71), anger (.75), and hostility (.83) were also adequate. We again compared the six-factor model to several alternative models (see Table I). A w2 difference test revealed that the six-factor model provided a significantly better fit than combining rumination and mindfulness into a single factor, supporting the discriminant validity of rumination and mindfulness as distinct constructs. Combining the aggression factors into a single factor also created a significantly worse fit, confirming previous work on the discriminant validity of these separate facets of aggression. The six-factor model also fit significantly better than treating a two-factor model of rumination/mindfulness and aggression. In addition, a single factor model fit significantly less well than the proposed six-factor model, revealing that the distinctions among these constructs account for more data than a single factor of self-report. Thus, theoretically tenable alternative models fit the data less well than the proposed six-factor model. 2

We again initially tested a measurement model that included the reflection subscale, as well as rumination, mindfulness, and the four aggression variables. Allowing these seven factors to intercorrelate, the model fit the data well, w2(1154) 5 1865.41, CFI 5 .84, RMSEA 5 .058. The twelve reflection items all had high loadings (ls from .57 to .80). However, the reflection scale showed small and nonsignificant correlations with all factors (rso.15), including rumination (r 5 .06, ns). Therefore, the reflection subscale was not included in subsequent models.

Mindfulness and Rumination

Participants again endorsed a moderate level of rumination and mindfulness (see Table II). This sample showed a smaller range on the mindfulness measure. Specifically, no one in this sample averaged below three on the 6-point scale, whereas undergraduates in the first sample ranged from 1.2 to 5.8. With this sample, physical aggression, anger and, hostility averages were significantly lower than values in Study 1 (using one-sample t-tests, Pso.05); only verbal aggression was endorsed at a similar level as in Study 1. The ranges of the aggression subscales and rumination measure were similar across both samples. Rumination showed strong negative correlations with trait mindfulness (see Table III). Both rumination and trait mindfulness showed strong correlations with all four aggression subscales. Mediation models. The path model with the aggression subscales regressed on trait mindfulness fit the data adequately, w2(288) 5 468.88, Po.001, RMSEA 5 .060, CFI 5 .89. Specifically, trait mindfulness was a significant predictor of all four aggression subscales. When we added rumination as a potential mediator variable, the model fit was again adequate, w2(649) 5 1047.85, Po.001, RMSEA 5 .058, CFI 5 .88. Finally, we added age and gender to the models as covariates. The initial model with mindfulness and aggression fit adequately, w2(330) 5 538.22, Po.001, RMSEA 5 .055, CFI 5 .87. The mediation model also fit the data adequately, w2(713) 5 1152.37, Po.001, RMSEA 5 .054, CFI 5 .87. Trait mindfulness significantly predicted rumination, b 5 .46, SE 5 .06, Po.001. Rumination significantly predicted verbal aggression, hostility, and anger, but not physical aggression (see Table IV). Trait mindfulness no longer significantly predicted any aggression subscale. Gender did not show any significant associations with mindfulness, rumination, or the aggression subscales (all bso.13). Older participants reported less rumination (b 5 .22, Po.01) and physical aggression (b 5 .25, Po.01). To look for evidence consistent with a mediating role for rumination, we first examined whether the bs between mindfulness and the aggression subscales decreased with the inclusion of rumination in the model. The inclusion of rumination in the model caused b estimates to decrease to nonsignificance for the associations between trait mindfulness and hostility (b dropped from .41 to .16), anger (a dropped from .23 to .03), and verbal aggression (b dropped from .24 to .08). As before, we also calculated indirect effect estimates and bias-corrected bootstrap estimates for the 95%

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confidence intervals (see Table IV). These data are consistent with the idea that rumination mediates the links between mindfulness and verbal aggression, hostility, and anger. In sum, this study served as a replication of Study 1 with a nonundergraduate sample. Even after including age and gender as covariates in the model, the pattern of correlations was consistent with rumination again partially mediating the associations between mindfulness and both anger and hostility. This time, analyses also suggested that rumination may partially mediate the link between mindfulness and verbal aggression. Once again, the pattern was not consistent with rumination mediating the relationship between mindfulness and physical aggression. Implications of these results will be discussed below. Why rumination correlated with physical and verbal aggression in this sample and not in the undergraduate sample is unclear. This particular sample showed a slightly larger variance on the rumination measure, which might explain the larger correlations. Alternatively, perhaps other factors than rumination best predict tendencies for aggressive behavior in younger, undergraduate populations. For example, alcohol consumption and emotional vulnerability are associated with increased aggressive behavior [Caprara et al., 1987; Chermack and Giancola, 1997]. These constructs may influence college-aged students more than adults who are older and working. Although data on aggression in children are plentiful, age-related differences in predictors of aggression have not been identified as frequently in adults [e.g., Hennessy and Wiesenthal, 2004]. Future research should investigate the predictors of behavioral aggression in adults of different ages.

GENERAL DISCUSSION

This pair of studies explored whether rumination might potentially mediate the association between mindfulness and several aggression-related variables. SEM analyses allowed us to confirm the factor structures of rumination and mindfulness and to ensure that they are in fact distinct constructs. Moreover, we examined physical aggression, verbal aggression, anger, and hostility separately, rather than as one composite measure of aggression. These studies therefore yield important new information about the potential of mindfulness to decrease both rumination and the behavioral, emotional, and cognitive components of aggression. Aggr. Behav.

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With two different samples, we found that people who are mindful are less angry and hostile. Moreover, our results are consistent with the proposed model that the relationships between mindfulness and anger and hostility are partly mediated by lower levels of ruminative thinking. Only two previous studies have examined the links between mindfulness, hostility, and anger [Brown and Ryan, 2003; Heppner et al., 2008]. The current studies therefore provide important initial evidence that mindfulness may contribute to decreased anger and hostility. Moreover, this is the first study we know of to suggest that mindfulness might reduce anger and hostility through its effect on rumination. Only one other study has found that decreased rumination following mindfulness training accounted for decreased depressive and anxious symptoms [Ramel et al., 2004]. Therefore, our results provide necessary additional evidence that rumination may be one mechanism of mindfulness. Mindfulness was also associated with less physical and verbal aggression in both of our studies. Two previous case studies found that teaching mindfulness decreased aggressive behavior [Singh et al., 2007a,b]. Our studies therefore provide needed statistical support for the relationship between mindfulness and behavioral aggression. Experimental work should be a focus of future studies. The potential role of rumination in these relationships, however, is less clear. Results were consistent with rumination mediating the association between mindfulness and verbal aggression only for our nonundergraduate sample. Moreover, contrary to predictions, the pattern of correlations did not suggest that rumination might mediate the relationship between mindfulness and physical aggression. In the undergraduate sample, the lack of support for mediation might be due to weak and nonsignificant correlations between rumination and overt aggression. However, rumination was associated with both physical and verbal aggression in the nonundergraduate sample. Despite this, the results did not support the proposed model that rumination would mediate the link between mindfulness and physical aggression. Therefore, it seems that rumination may not constitute a major mechanism through which mindfulness affects verbal and especially physical aggression. Several other proposed mechanisms for mindfulness may influence behavioral aggression. Relaxation is one common outcome of mindfulness practice [for a review, see Baer, 2003]. Studies have also found that relaxation can decrease aggression, presumably because relaxation decreases physiological arousal Aggr. Behav.

[Lopata, 2003; Tyson, 1998]. Thus, mindfulness practice may decrease aggression partially through making individuals more relaxed. Another possible mechanism between mindfulness and behavioral aggression is emotion regulation, or the ability to influence the experience and expression of emotions [Gross, 1998]. Common emotion regulation strategies include altering thoughts or behavior in order to better cope with negative emotions. Two studies have found that mindfulness correlates with the ability to regulate negative affect [Brown and Ryan, 2003; Coffey and Hartman, 2008]. Moreover, Coffey and Hartman [2008] found that emotion regulation mediated the association between mindfulness and depressive and anxious symptoms. Likewise, research has found links between aggressive behavior and poor emotion regulation [e.g., Izard et al., 2008; McNulty and Hellmuth, 2008]. Thus, mindfulness may decrease aggressive behavior in part because it promotes the ability to cope with and even change negative internal emotions. Mindfulness may also promote better cognitive functioning and flexibility. As discussed above, mindfulness is associated with increased cognitive flexibility [Davis and Nolen-Hoeksema, 2000]. A recent study also showed that participating in mindfulness training led to increases in working memory and sustained attention [Chambers et al., 2008]. Some researchers in fact suggest that mindfulness is a form of ‘‘mental training’’ that involves self-regulation of attention and cognitive inhibition [Bishop et al., 2004]. On the other hand, aggression is associated with decreased cognitive performance, especially on tests of planning, attentional control, and goal-directed behavior [Giancola, 2000]. Thus, mindfulness may actually promote better executive functioning, which may prevent some of the cognitive errors that contribute to aggressive behavior. Relatedly, mindfulness may decrease aggression because it decreases behaving in automatic or impulsive ways. Mindfulness should help make people aware of feelings and thoughts when they arise, rather than after they are already acted upon. This may be especially important when emotional association networks get activated, as in the case of a perceived provocation. As Ryan and Deci [2000] suggest, an open awareness is necessary for choosing actions that coincide with one’s values, needs, and best interest. Initial evidence in fact suggests that mindfulness is positively associated with valueconcordant behavior and negatively associated with impulsivity [Brown and Ryan, 2003]. Future studies should explore these and other potential

Mindfulness and Rumination

mechanisms of the relationship between mindfulness and behavioral aggression. The current studies also suggest important information about the construct of mindfulness. Our use of SEM analyses allowed us to confirm the single-factor structure of the MAAS. In both samples, the mindfulness items assessing awareness of internal states showed the weakest factor loadings, whereas items tapping intentional attention had the strongest factor loadings. These findings concur with a recent item response analysis suggesting that the MAAS most clearly measures automaticity [Van Dam et al., 2009; see also MacKillop and Anderson, 2007]. Additionally, mindfulness shared no variance with reflection, suggesting that mindfulness is not related to selfanalysis or philosophical introspection [see also Brown and Ryan, 2003]. Interestingly, both samples showed the same mean level of mindfulness and similar correlations between mindfulness and other study variables. These similarities across samples suggest that the MAAS functions similarly across populations with and without extensive knowledge about mindfulness. Brown and Ryan [2004] in fact suggest that mindfulness is an inherent, individual capacity, rather than a product of any behavioral practice like meditation. Future research should investigate the meaning of self-reported mindfulness and the associations between mindfulness, spiritual beliefs, and meditation experience in different populations. This study possessed some methodological limitations that should be addressed in future research. As stated above, statistical tests of mediation with cross-sectional data cannot illuminate the temporal associations between study variables. Thus, although we proposed that mindfulness contributes to decreased rumination, which in turn contributes to decreased anger, hostility, and aggression, our results cannot rule out other possibilities. For instance, high levels of rumination could make people less mindful, which might lead to increased subsequent anger, hostility, and aggression. It does seem theoretically plausible that people who abstain from the repetitive and inflexible process of rumination have more available attention for the present moment. However, we know of no experimental studies that have examined this possibility. Moreover, experimental studies suggest that increased mindfulness causes reductions in rumination [Ramel et al., 2004; Shapiro et al., 2008], indicating the same directionality that we proposed. Future research could examine the temporal association between mindfulness and rumination. Alternatively, our results cannot rule out the possibility that low aggressive tendencies might cause

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individuals to engage in high levels of mindfulness and low levels of rumination. However, substantial experimental evidence suggests that higher levels of rumination in fact cause increased behavioral aggression, compared with lower levels of rumination [Bushman, 2002; Bushman et al., 2005; Rusting and Nolen-Hoeksema, 1998]. We know of no studies showing that manipulated aggression increases subsequent rumination. Likewise, meditation training leads to decreased aggressive behavior [Heppner et al., 2008; Singh et al., 2007a,b]. Proposed mechanisms of mindfulness include intentional attention, cognitive and behavioral flexibility, selfregulation, and values clarification [Shapiro et al., 2006]. It seems much more likely that these mechanisms result in low aggressive tendencies than the other way around. Therefore, both empirical and theoretical work strongly suggest that aggressionrelated variables should be the DVs in our model. However, only longitudinal or experimental studies can rule out alternative possibilities. In addition, we included only self-report measures, which allowed the possibility of reporter bias. As with any study of aggression, participants may underreport aggressive attitudes or behaviors due to social norms. Both of our samples reported less physical aggression than in other published research [e.g., Buss and Perry, 1982]. Given that underreporting tendencies would diminish the likelihood of finding correlations, these data may actually underestimate true effects. Future studies should therefore include behavioral measures of aggression. However, this limitation does not pose a barrier to interpretation of our data. In sum, our studies contribute important new information about how mindfulness relates to rumination and aggression-related variables and suggest several hypotheses for future research. First, our results suggest theoretical hypotheses for how mindfulness might help a person respond to a provocation or triggering event. Specifically, present-focused and intentional attention may prevent the destructive cognitive and emotional cycles that occur following a perceived provocation. Associative network theories suggest that when a particular provoking trigger is experienced, related emotions, beliefs, and memories are brought to mind [Anderson and Bushman, 2002; Berkowitz, 1990]. Some research suggests that anger in particular produces a high amount of arousal and cognitive processing [Baumeister et al., 1990]. It is likely that people with a tendency to ruminate will harp on perceived provocations and possible revenge, thus keeping their aggressive association networks active Aggr. Behav.

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and increasing their likelihood of reporting hostile thoughts and angry feelings [Berkowitz, 1990; Rusting and Nolen-Hoeksema, 1998]. Mindfulness may help stop or even prevent this activation by keeping a person attentive to the present moment and preventing rumination about past provocations. Therefore, a mindful person may actually experience less anger and hostility following a triggering event, in part because of decreased rumination. Although the current studies suggest that rumination does not mediate the link between mindfulness and dispositional physical aggression, it is possible that rumination might be more related to situationally induced aggression. Thus, perhaps a mindful person would respond to an acute provocation with less rumination and subsequently less behavioral aggression. Alternatively, mindfulness might help a person respond to a provocation with less behavioral aggression through other mechanisms like relaxation or self-regulation. Many more experimental studies are needed to test these specific hypotheses. Our nonexperimental findings also have important implications for future anger management treatments. Interventions for anger problems typically include contingency management, stimulus control, or social skills training [Deffenbacher et al., 2002; Edmondson and Conger, 1996]. Mindfulness training may provide a good complement to these other important skills. By increasing awareness of current emotions, thoughts, and situations, mindfulness may help promote acceptance, distress tolerance, and intentional attention. These emotion regulation skills provide a solid foundation for skills training. Recent clinical interventions have incorporated mindfulness training in treatments for depressive relapse, chronic pain, anxiety, borderline personality disorder, and relapse prevention in substance abusers [see Baer, 2003 for a review]. The nonexperimental results presented here suggest the hypothesis that mindfulness training may also enhance treatments for anger problems. Future research studies should empirically test the benefit of adding mindfulness training to anger management interventions.

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