Philadelphia Mindfulness Scale (PHLMS)

Abstract

The Philadelphia Mindfulness Scale (PHLMS) is a 20-item psychometric instrument developed by LeeAnn Cardaciotto, James D. Herbert, Evan M. Forman, Eunyoe Moitra, and Valerie Farrow (2008) to assess mindfulness as a bi-dimensional construct comprising Present-Moment Awareness and Acceptance. Grounded in the operational consensus definition proposed by Bishop et al. (2004), the instrument was intentionally constructed to decouple continuous perceptual monitoring of ongoing internal and external experiences from an open, non-judgmental stance toward those phenomena. Unlike unitary measures such as the Mindful Attention Awareness Scale (MAAS), which primarily quantify attention lapses, or complex multi-faceted instruments such as the Five Facet Mindfulness Questionnaire (FFMQ), the PHLMS provides a parsimonious, dual-component operationalization suitable for clinical and non-clinical populations.

Each dimension is assessed via 10 items scored on a 5-point Likert-type frequency scale ranging from 1 (never) to 5 (very often). The Acceptance items are framed to capture experiential avoidance and non-acceptance, requiring reverse scoring such that higher aggregate scores indicate greater psychological acceptance. Psychometric evaluations demonstrate robust internal consistency across undergraduate, community, and psychiatric outpatient samples, with Cronbach’s alpha coefficients typically ranging from .75 to .87 for Awareness and from .75 to .88 for Acceptance. Confirmatory factor analyses consistently substantiate a two-factor orthogonal or weakly correlated structure ($r = -.08$ to $.12$ in non-clinical cohorts), confirming that self-monitored awareness and psychological acceptance function as distinct cognitive-behavioral processes. This article provides an exhaustive psychometric review of the PHLMS, delineating its theoretical architecture, validation trajectories, reliability statistics, structural factor analyses, scoring parameters, and clinical utility across diverse populations.

Keywords

Philadelphia Mindfulness Scale, PHLMS, Mindfulness Assessment, Present-Moment Awareness, Acceptance, Experiential Avoidance, Psychometrics, Factor Analysis, Construct Validity, Cognitive Behavioral Therapy

Authors

The Philadelphia Mindfulness Scale was constructed and psychometrically validated by a research team centered at Drexel University (Philadelphia, Pennsylvania, United States):

• LeeAnn Cardaciotto, Ph.D. — Department of Psychology, Drexel University; currently Professor of Psychology at LaSalle University. Her empirical work focuses on mindfulness, acceptance-based interventions, behavioral assessment, and the psychometric measurement of contemplative processes.
• James D. Herbert, Ph.D. — Department of Psychology, Drexel University; currently President of the University of New England. An authority on cognitive behavioral therapy (CBT), Acceptance and Commitment Therapy (ACT), anxiety disorders, and evidence-based clinical practices.
• Evan M. Forman, Ph.D. — Professor of Psychology and Director of the Center for Weight, Eating, and Lifestyle Science (WELL Center) at Drexel University. His expertise includes mechanisms of behavioral change, health psychology, and acceptance-based behavioral therapies.
• Eunyoe Moitra, Ph.D. — Department of Psychology, Drexel University; currently Associate Professor (Research) at the Warren Alpert Medical School of Brown University. Specializes in behavioral medicine, psychiatric comorbidities, and acceptance-based approaches to chronic health conditions.
• Valerie Farrow, B.A. — Clinical research coordinator and graduate investigator at Drexel University, contributing to scale development, item generation, and psychometric validation.

Purpose

The primary objective of the Philadelphia Mindfulness Scale is to provide an empirically rigorous, theory-driven, and clinically practical measurement tool capable of independently capturing the two foundational pillars of mindfulness: continuous present-moment awareness and non-evaluative psychological acceptance. Prior to the development of the PHLMS, psychological researchers encountered major psychometric dilemmas when attempting to quantify mindfulness. Existing instruments exhibited divergent conceptual definitions. Some instruments conflated attention with acceptance, while others collapsed distinct mindfulness facets into an undifferentiated single score that obscured clinical mechanisms.

For example, the Mindful Attention Awareness Scale (Brown & Ryan, 2003) operationalizes mindfulness almost exclusively as undivided attentiveness to present reality, explicitly excluding acceptance under the assumption that open attention inherently presupposes acceptance. Conversely, clinical models such as Dialectical Behavior Therapy (DBT; Linehan, 1993) and Acceptance and Commitment Therapy (ACT; Hayes et al., 1999) demonstrate that hyper-awareness of internal sensations—such as heart palpitations, catastrophic thoughts, or emotional surges—can exacerbate psychiatric distress if accompanied by experiential avoidance, suppression, or emotional resistance. Individuals with panic disorder, health anxiety, or PTSD often demonstrate elevated or hypervigilant present-moment somatic monitoring without corresponding acceptance, producing clinical deterioration rather than psychological flexibility.

Cardaciotto et al. (2008) designed the PHLMS to resolve this measurement challenge by achieving three key aims:

• Operational Alignment: Directly operationalize the operational consensus definition formulated by Bishop et al. (2004), establishing independent scales for attentional monitoring and open orientation to experience.
• Orthogonal Measurement: Enable clinicians and researchers to independently quantify Awareness and Acceptance, allowing researchers to evaluate whether mindfulness interventions (e.g., Mindfulness-Based Stress Reduction [MBSR] or Mindfulness-Based Cognitive Therapy [MBCT]) cultivate both dimensions synchronously or differentially across treatment trajectories.
• Clinical Differentiation: Provide a practical tool that avoids confounding mindful presence with positive emotional states, social desirability, or esoteric spiritual jargon, ensuring broad applicability across general psychiatric outpatients, medical patients, and non-clinical cohorts.

Psychological Construct

The PHLMS conceptualizes mindfulness not as an indivisible, monolithic trait, but as a bi-dimensional behavioral orientation consisting of two functionally distinct, interactive cognitive processes: Present-Moment Awareness and Acceptance.

1. Present-Moment Awareness

Present-Moment Awareness represents the conscious, sustained monitoring of one’s immediate, ongoing psychological and environmental experience. It involves allocating attentional resources to internal sensations (e.g., physiological responses, emotional shifts, streams of cognition) and external sensory stimuli (e.g., visual cues, ambient sounds, tactile sensations) as they unfold in real time. Items indexing this construct (Items 1, 3, 5, 7, 9, 11, 13, 15, 17, and 19) capture distinct facets of perceptual tracking:

• Cognitive Monitoring: Recognizing the flow of cognitions as mental events rather than fused realities (e.g., Item 1: “I am aware that thoughts are passing through my mind”; Item 13: “I am aware of thoughts I’m having when my mood changes”).
• Interoceptive and Somatic Sensitivity: Tracking physiological fluctuations, visceral states, and bodily arousal without automated dissociation (e.g., Item 7: “When I am startled, I notice what is going on inside my body”; Item 15: “I notice changes inside my body, like my heart beating faster or my muscles getting tense”).
• Exteroceptive Sensory Attunement: Maintaining sensory contact with physical surroundings during everyday activities (e.g., Item 5: “When I shower, I am aware of how the water is running over my body”; Item 9: “When I walk outside, I am aware of smells or how the air feels against my face”).
• Interpersonal Attentiveness: Recognizing behavioral cues and emotional expressions in social environments (e.g., Item 3: “When talking with other people, I am aware of their facial and body expressions”; Item 19: “When talking with other people, I am aware of the emotions I am experiencing”).

2. Acceptance

Acceptance reflects an open, non-defensive, and non-judgmental stance toward ongoing internal experiences, characterized by the willingness to experience unpleasant thoughts, feelings, and physiological sensations without attempting to modify, avoid, escape, or suppress them. Rather than indicating passive resignation, fatalism, or behavioral inaction, acceptance is an active, functional posture of psychological non-resistance. In the PHLMS, all 10 Acceptance items (Items 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20) are explicitly keyed in the direction of non-acceptance, cognitive fusion, and experiential avoidance, which are subsequently reverse-scored:

• Emotional Distraction and Avoidance: Engaging in deliberate diversionary behaviors to evade aversive affective states (e.g., Item 2: “I try to distract myself when I feel unpleasant emotions”; Item 20: “When I have a bad memory, I try to distract myself to make it go away”).
• Experiential Suppression: Deliberately stifling intrusive or distressful memories, topics, or self-evaluations (e.g., Item 4: “There are aspects of myself I don’t want to think about”; Item 12: “There are things I try not to think about”; Item 18: “I try to put my problems out of my mind”).
• Judgmental Self-Correction and Invalidation: Applying prescriptive cognitive rules that condemn normal emotional reactions (e.g., Item 10: “I tell myself that I shouldn’t have certain thoughts”; Item 14: “I tell myself that I shouldn’t feel sad”).
• Impulsive Behavioral Escape: Compulsive activity used as an affective barrier against internal experiencing (e.g., Item 6: “I try to stay busy to keep thoughts or feelings from coming to mind”; Item 8: “I wish I could control my emotions more easily”).

Theoretical Framework

The architectural foundation of the PHLMS is anchored in modern contemporary behavioral and cognitive paradigms, specifically the operational definition put forward by the Bishop et al. (2004) consensus panel. Bishop and colleagues conceptualized mindfulness as a two-component process:

1. The self-regulation of attention directed toward immediate experience, enabling sustained vigilance, mental flexibility, and attentional switching.
2. Adopting a particular orientation toward one’s experiences characterized by curiosity, openness, and acceptance.

Prior psychometric tradition often treated these components as an indivisible psychological trait. However, Cardaciotto and colleagues (2008) highlighted critical theoretical tensions between attention and acceptance. Drawing from Relational Frame Theory (RFT) and the psychological flexibility model of Acceptance and Commitment Therapy (Hayes, Strosahl, & Wilson, 1999), the authors recognized that attention alone can be deployed rigidly, defensively, or hyper-reflectively. In conditions characterized by high internal distress (e.g., generalized anxiety disorder, hypochondriasis, obsessive-compulsive spectrums), individuals often display elevated present-moment internal awareness coupled with severe experiential aversion. When an individual notices their physiological changes without cultivating an attitude of radical acceptance (Linehan, 1993), that increased awareness can escalate panic symptoms and cognitive catastrophic misinterpretations.

Furthermore, the construct validity of mindfulness instruments has historically suffered from conflating trait mindfulness with psychological symptoms or psychological well-being. For instance, several items on early scales required respondents to report absentmindedness or general cognitive failures (e.g., breaking objects, forgetting people’s names), which may measure generalized cognitive efficiency, executive dysfunction, or depression rather than mindful attention per se. The PHLMS addressed this theoretical confound by constructing items that describe neutral, experiential behaviors (e.g., feeling water in the shower, noticing bodily tension, observing thoughts passing) devoid of clinical value judgments. Consequently, the PHLMS permits the empirical discovery of how awareness and acceptance dynamically interact across diverse clinical psychopathologies.

Validity

The psychometric validity of the PHLMS has been rigorously tested across non-clinical college populations, general adult community cohorts, and structured clinical samples suffering from mood, anxiety, and eating disorders.

1. Construct and Convergent Validity

Convergent validity has been established by correlating PHLMS subscales with established measures of mindfulness, emotional regulation, and psychological distress:

• Awareness Subscale: Correlates moderately to strongly with the Mindful Attention Awareness Scale (MAAS; $r = .30$ to $.45$, depending on sample characteristics), the Kentucky Inventory of Mindfulness Skills (KIMS) Observe subscale ($r = .56$ to $.68$), and self-reported Private Self-Consciousness ($r = .42$). Crucially, Awareness correlates weakly or near zero with measures of experiential avoidance (AAQ-II) and neuroticism, demonstrating that present-moment attunement can occur independently of affective distress.
• Acceptance Subscale: Demonstrates strong negative correlations with the Acceptance and Action Questionnaire (AAQ; $r = -.58$ to $-.71$), indicating that the reverse-scored PHLMS Acceptance scale accurately indexes low experiential avoidance and psychological non-reactivity. It also correlates positively with the KIMS Accept Without Judgment subscale ($r = .52$ to $.64$) and emotional clarity measures.

2. Discriminant Validity

One of the strongest psychometric features of the PHLMS is the discriminant independence between its two constituent factors. In non-clinical development samples (Cardaciotto et al., 2008), the intercorrelation between the Awareness subscale and the Acceptance subscale was near zero ($r = -.08$, $p > .05$ in Sample 1; $r = .04$, $p > .05$ in Sample 2). In psychiatric outpatient samples, the correlation remains negligible to weak ($r = -.14$ to $.10$), empirically validating the theoretical hypothesis that an individual’s propensity to monitor present-moment sensations does not automatically imply non-judgmental acceptance of those experiences.

Moreover, the two subscales display divergent patterns of association with psychological distress:

• The Acceptance subscale consistently exhibits strong negative correlations with depressive symptomatology on the Beck Depression Inventory (BDI-II; $r = -.45$ to $-.58$), generalized anxiety on the Beck Anxiety Inventory (BAI; $r = -.38$ to $-.52$), and perceived stress ($r = -.49$).
• The Awareness subscale shows negligible or slightly positive correlations with general anxiety ($r = .05$ to $.15$) and somatic vigilance, confirming that elevated perceptual monitoring without acceptance does not confer psychological relief.

3. Criterion and Incremental Validity

The PHLMS shows robust incremental validity in predicting clinical symptoms beyond global neuroticism and demographic variables. Regression analyses by Forman et al. (2007) and Cardaciotto et al. (2008) showed that PHLMS Acceptance accounted for significant unique variance in psychological distress, functioning, and quality of life after controlling for age, sex, and trait negative affect. In longitudinal and treatment-outcome designs, changes in Acceptance mediate clinical improvements observed during Acceptance and Commitment Therapy and Mindfulness-Based Cognitive Therapy.

Reliability

The PHLMS exhibits strong, stable internal consistency and temporal reliability across multiple independent empirical investigations.

1. Internal Consistency

During original scale development across undergraduate university samples ($N = 620$ and $N = 348$) and psychiatric outpatient samples ($N = 98$), internal consistency estimates met or exceeded rigorous psychometric thresholds:

• Awareness Subscale: Cardaciotto et al. (2008) reported a Cronbach’s alpha ($lpha$) of .85 in the primary student development sample, .87 in a cross-validation student sample, and .80 in an outpatient psychiatric clinical sample. International adaptations (e.g., German validation by Ziemer et al., 2019; Spanish validation by Cebolla et al., 2012; Persian validation by Kakavand et al., 2016) report alpha coefficients ranging between .78 and .86.
• Acceptance Subscale: Cardaciotto et al. (2008) observed Cronbach’s alphas of .86 in the primary development sample, .87 in the cross-validation cohort, and .82 in the clinical outpatient cohort. Cross-cultural adaptations report internal consistency coefficients ranging between .75 and .89.
• Composite Reliability: Studies applying McDonald’s omega ($\omega$) confirm that factor saturation is high, with $\omega$ values consistently exceeding .82 for both latent constructs, demonstrating that item variance is driven by the intended underlying factors.

2. Test-Retest Reliability

Temporal stability was evaluated across multiple intervals to ensure that the PHLMS captures stable trait dispositions while remaining sensitive to clinical intervention:

• Over a one-week retest interval ($N = 78$), Pearson product-moment correlations showed excellent stability: $r = .80$ ($p < .001$) for Awareness, and$r = .85$ ($p < .001$) for Acceptance.
• Over a two-to-four-week retest interval, stability coefficients remained solid ($r = .72$ to $.79$ across subscales), demonstrating that baseline scores are reliable traits over time in the absence of mindfulness meditation training or therapeutic intervention.

Factor Analysis

The structural validity of the PHLMS was refined using both Exploratory Factor Analysis (EFA) and rigorous Confirmatory Factor Analysis (CFA).

1. Exploratory Factor Analysis (EFA)

Initial item generation yielded a broad pool of 114 candidate mindfulness statements derived from clinical theory, contemplative traditions, and consensus definitions. Successive principal axis factor extractions with oblimin and varimax rotations were conducted. The scree test, parallel analysis, and Kaiser-Guttman eigenvalue criteria consistently indicated a two-factor latent architecture. Successive iterations removed items that exhibited cross-loadings (> .30 on secondary factors), low primary factor saturation (< .40), or conceptual redundancies. This process condensed the instrument into the final 20-item scale, consisting of 10 pure items loading on Factor 1 (Awareness) and 10 pure items loading on Factor 2 (Acceptance).

2. Confirmatory Factor Analysis (CFA)

Cardaciotto et al. (2008) tested three competing structural models using maximum likelihood structural equation modeling:

1. Unidimensional Model: All 20 items loading onto a single general mindfulness construct. This model yielded unacceptable fit ($\chi^2/df > 6.5$, $ ext{RMSEA} > .12$,$ ext{CFI} < .70$), rejecting the idea that mindfulness is a single undifferentiated dimension.
2. Two-Factor Correlated Model: 10 items loading on Awareness and 10 items loading on Acceptance, with the inter-factor correlation freely estimated. This model provided excellent fit across both non-clinical and psychiatric outpatient samples. Model fit indices confirmed structural integrity: $\chi^2(169) = 328.45$, $p < .001$;$ ext{Root Mean Square Error of Approximation (RMSEA)} = .049$ ($90% ext{ CI } [.042, .056]$); $ ext{Comparative Fit Index (CFI)} = .94$;$ ext{Tucker-Lewis Index (TLI)} = .93$; and$ ext{Standardized Root Mean Square Residual (SRMR)} = .051$.
3. Two-Factor Orthogonal Model: In non-clinical cohorts, fixing the covariance between Awareness and Acceptance to zero produced minimal change in fit ($\Delta \chi^2$ non-significant), substantiating the near-independence of these psychological tendencies.

Standardized item factor loadings for the Awareness factor range from .48 to .76 (e.g., Item 1: .65; Item 5: .58; Item 15: .72; Item 17: .76). Standardized loadings for the Acceptance factor range from .47 to .78 (e.g., Item 2: .68; Item 4: .61; Item 10: .74; Item 14: .71; Item 20: .73). Cross-cultural CFA replications in Spain, Germany, China, and Italy have affirmed this two-factor solution without needing substantial residual error covariances.

Instrument / Measurement Tool

• Test Type: Self-report psychological scale / trait questionnaire.
• Administration Format: Paper-and-pencil questionnaire or computerized self-administered survey.
• Target Population: Adults and adolescents aged 16 and older; validated in clinical psychiatric settings, medical patients, and non-clinical general populations.
• Completion Time: Approximately 3 to 5 minutes.
• Item Count: 20 items total (10 items assessing Awareness; 10 items assessing Acceptance).
• Response Scale: 5-point Likert-type frequency scale:
  • 1 = never
  • 2 = rarely
  • 3 = sometimes
  • 4 = often
  • 5 = very often
• Subscale Allocation:
  • Awareness Subscale: Items 1, 3, 5, 7, 9, 11, 13, 15, 17, and 19.
  • Acceptance Subscale: Items 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20.
• Scoring Protocol and Calculations:
  • Reverse Scoring: All 10 items on the Acceptance subscale are negatively keyed experiential avoidance statements. They must be reverse scored prior to calculating subscale sums: $1
    ightarrow 5$, $2
    ightarrow 4$, $3
    ightarrow 3$, $4
    ightarrow 2$, $5
    ightarrow 1$.
  • Subscale Score Derivation: Calculate the sum or mean of the 10 Awareness items (score range: 10 to 50) and the sum or mean of the 10 reverse-coded Acceptance items (score range: 10 to 50). Higher scores denote greater present-moment awareness and greater psychological acceptance, respectively.
  • Caution on Total Composite Score: Because Awareness and Acceptance are empirically orthogonal in non-clinical samples and correlate weakly in clinical groups, computing a single collapsed “total mindfulness” score is not recommended. Doing so obscures distinct profiles, such as individuals high in internal awareness but low in acceptance (typical in panic or health anxiety).

Permissions & Fee and Test Year

The Philadelphia Mindfulness Scale was formally published in 2008 by LeeAnn Cardaciotto, James D. Herbert, Evan M. Forman, Eunyoe Moitra, and Valerie Farrow in the peer-reviewed journal Assessment (Sage Publications), following Cardaciotto’s 2005 doctoral dissertation work at Drexel University. The PHLMS is classified as an open-access psychometric instrument for non-commercial academic research and clinical assessment purposes.

No licensing fees, user registration charges, or royalty payments are required when administering the scale for scientific research, clinical therapy evaluation, or higher educational instruction, provided that appropriate scholarly attribution is cited. For commercial deployment, inclusion in for-profit proprietary digital applications, or commercial test battery republication, formal copyright clearance should be directed to the copyright holder (Sage Publications or the primary authors).

References

• Bishop, S. R., Lau, M., Shapiro, S., Carlson, L., Anderson, N. D., Carmody, J., Segal, Z. V., Abbey, S., Speca, M., Velting, D., & Devins, G. (2004). Mindfulness: A proposed operational definition. Clinical Psychology: Science and Practice, 11(3), 230–241. https://doi.org/10.1093/clipsy.bph077
• Brown, K. W., & Ryan, R. M. (2003). The benefits of being present: Mindfulness and its role in psychological well-being. Journal of Personality and Social Psychology, 84(4), 822–848. https://doi.org/10.1037/0022-3514.84.4.822
• Cardaciotto, L. (2005). Assessing mindfulness: The development of a bi-dimensional measure of awareness and acceptance (Doctoral dissertation). Drexel University, Philadelphia, PA. Dissertation Abstracts International, 66(06B), 3402.
• Cardaciotto, L., Herbert, J. D., Forman, E. M., Moitra, E., & Farrow, V. (2008). The assessment of present-moment awareness and acceptance: The Philadelphia Mindfulness Scale. Assessment, 15(2), 204–223. https://doi.org/10.1177/1073191107311461
• Cebolla, A., García-Palacios, A., Soler, J., Guillen, V., Baños, R., & Botella, C. (2012). Psychometric properties of the Spanish validation of the Philadelphia Mindfulness Scale. The Spanish Journal of Psychology, 15(3), 1445–1453. https://doi.org/10.5209/rev_sjop.2012.v15.n3.39423
• Forman, E. M., Herbert, J. D., Moitra, E., Yeomans, P. D., & Geller, P. A. (2007). A randomized controlled effectiveness trial of acceptance and commitment therapy and cognitive therapy for anxiety and depression. Behavior Modification, 31(6), 772–799. https://doi.org/10.1177/0145445507302202
• Hayes, S. C., Strosahl, K. D., & Wilson, K. G. (1999). Acceptance and commitment therapy: An experiential approach to behavior change. Guilford Press.
• Linehan, M. M. (1993). Cognitive-behavioral treatment of borderline personality disorder. Guilford Press.
• Ziemer, J., Rogoll, J., Baus, N., & Moosdorf, F. (2019). Psychometric validation and factor structure of the German version of the Philadelphia Mindfulness Scale. Frontiers in Psychology, 10, 2415. https://doi.org/10.3389/fpsyg.2019.02415

13. Items of the Scale (Questionnaire)