Index of Core Spiritual Experiences

1. Abstract

The Index of Core Spiritual Experiences (INSPIRIT) is an influential psychometric instrument developed by Jared D. Kass, Richard Friedman, Jane Leserman, Patricia C. Zuttermeister, and Herbert Benson (1991) to assess concrete, highly transformative spiritual experiences. Conceived within the multidisciplinary context of behavioral medicine and psychosomatic health at Harvard Medical School and the Mind/Body Medical Institute, the INSPIRIT was designed to bypass abstract doctrinal allegiances, ecclesiastical affiliations, or vague religious sentiments. Instead, it operationalizes two defining hallmarks of authentic spiritual experiences: (a) a discrete, identifiable event accompanied by a cognitive appraisal that solidifies personal conviction in the existence of God or an ultimate transcendent reality, and (b) an internalized perception of an immediate, unitive, or intimate relationship with the divine (the subjective sense that God dwells within and that one experiences profound closeness to this ultimate presence).

The instrument comprises seven primary items, including a multi-faceted experiential checklist (Item 7) cataloging specific transpersonal, mystical, and unitive phenomena (e.g., encounters with transcendent spiritual figures, profound inner peace, near-death events, and perceived divine healings). Responses are scored on a standardized 4-point metric, yielding an overall composite index ranging from 1.00 to 4.00, where scores of 3.50 and above indicate unequivocal occurrences of core spiritual experiences. Psychometrically, the INSPIRIT demonstrates robust internal consistency (Cronbach’s α = .88–.90) and a stable unidimensional structure accounting for over 63% of total variance in original principal components analyses. Extensive construct, convergent, and discriminant validation studies have established its capacity to differentiate experienced meditators from novices, its strong positive alignment with intrinsic religious motivation (r = .61–.69), its inverse association with extrinsic religiosity, and its clinical utility as a predictive correlate of psychological well-being, resilience, and medical symptom reduction.

2. Keywords

Index of Core Spiritual Experiences, INSPIRIT, spirituality assessment, mystical experiences, intrinsic religiosity, behavioral medicine, psycho-oncology, transpersonal psychology, psychometrics, mind-body medicine, spiritual well-being, religious coping.

3. Authors

The INSPIRIT was formulated through an academic collaboration between clinical psychologists, behavioral researchers, and physicians associated with the Mind/Body Medical Institute, Harvard Medical School, New England Deaconess Hospital, and affiliated research institutions:

• Jared D. Kass, Ph.D. – Lead investigator; Professor of Counseling and Psychology at Lesley University; formerly Research Associate at the Mind/Body Medical Institute, New England Deaconess Hospital, Harvard Medical School.
• Richard Friedman, Ph.D. – Research Associate in Behavioral Medicine, Division of Behavioral Medicine, New England Deaconess Hospital; Associate Professor of Psychiatry and Behavioral Science, State University of New York at Stony Brook.
• Jane Leserman, Ph.D. – Sociologist and Methodologist; Research Professor of Psychiatry, Department of Psychiatry, School of Medicine, University of North Carolina at Chapel Hill.
• Patricia C. Zuttermeister, M.S. – Biostatistician; Mind/Body Medical Institute, New England Deaconess Hospital, Harvard Medical School.
• Herbert Benson, M.D. – Pioneer of mind-body medicine; Founding President of the Mind/Body Medical Institute; Mind/Body Medical Institute Associate Professor of Medicine, Harvard Medical School; author of The Relaxation Response.

4. Purpose

For decades, empirical inquiries into the psychology of religion were impeded by crude measurement tools. Most epidemiological surveys conflated spirituality with sociological indices such as nominal church membership, denomination, or frequency of attendance at public worship services. These demographic variables consistently failed to capture the subjective, phenomenological depth of direct spiritual or mystical awareness. The primary intent behind the development of the Index of Core Spiritual Experiences (INSPIRIT) was to construct an empirically rigorous, non-sectarian, self-report instrument capable of identifying personal spiritual encounters that are qualitatively distinct, emotionally charged, and cognitively transformative.

The theoretical rationale rests on the hypothesis that experiential spirituality exerts a profoundly different psychoneuroimmunological and psychological impact than passive dogmatic adherence. While dogmatic or extrinsic religious participation may occasionally engender cognitive dissonance, guilt, or rigid social compliance, direct mystical or spiritual encounters frequently evoke profound states of relaxation, psychological security, positive affective states, and an existential reorientation. Thus, the INSPIRIT was developed with two primary objectives:

1. To isolate and quantify discrete, core spiritual experiences that meet stringent experiential criteria: an identifiable perceptual event, a clear cognitive attribution confirming divine or transcendent reality, and an internalized sense of relational closeness or union with God.
2. To evaluate the empirical relationships linking these experiential markers to health-related variables, including chronic pain management, hypertension, psychological distress, immune function, and existential quality of life in clinical populations undergoing behavioral medicine interventions.

In clinical practice, the INSPIRIT serves as a brief, non-invasive diagnostic screening tool for pastoral care providers, clinical psychologists, and psycho-oncologists seeking to assess patients’ spiritual coping resources. Patients grappling with life-threatening medical diagnoses, terminal illness, or severe chronic pain frequently draw upon prior core spiritual experiences to make meaning of suffering, mitigate existential anxiety, and cultivate psychological resilience. In academic and epidemiological research, the scale provides a standardized index for cross-sectional and longitudinal investigations exploring the interplay between contemplative practices (such as mindfulness, centering prayer, or transcendental meditation), neuroendocrine modulation, and psychological well-being.

5. Psychological Construct

The INSPIRIT operationalizes the construct of a core spiritual experience as a multidimensional phenomenological event that alters an individual’s cognitive architecture, emotional state, and existential perspective. Unlike generalized spiritual attitudes or philosophical humanism, a core spiritual experience is characterized by two distinct, highly synchronized psychological components:

1. Distinct Event and Cognitive Appraisal of Divine Existence

This dimension reflects an explicit encounter wherein an individual experiences an altered state of consciousness, an emotional breakthrough, or a synchronistic occurrence that they directly attribute to an ultimate transcendent force or deity. The psychological significance of this process lies not merely in the sensory or affective trigger itself, but in the accompanying cognitive appraisal. The person interprets the event as unequivocal verification of a higher spiritual reality, resolving prior skepticism, ontological ambiguity, or theoretical detachment. This cognitive restructuring transitions the individual from an abstract “belief in God” to an experiential “conviction of God’s reality.” Examples include:

• An overpowering awareness of an intangible sacred presence or divine energy during contemplative prayer or nature immersion.
• A dramatic experiential resolution of existential despair characterized by feelings of profound inner peace or unconditioned joy.
• Apparitional or intuitive encounters with spiritual figures (such as Jesus, Mary, Buddha, or angelic beings).
• An encounter during a crisis or near-death state that solidifies conviction in an afterlife or higher spiritual consciousness.

2. Perception of an Internalized, Closeness-Oriented Divine Relationship

The second dimension assesses the subjective nature of the individual’s relational bond with the divine. The INSPIRIT differentiates between an extrinsic, distant, or punitive concept of God and an immanent, internalized relationship. In this state, the transcendent is perceived not as an external regulatory entity, but as an indwelling, loving, and supportive presence. This perception is marked by a deep sense of unitive closeness, emotional intimacy, and shared identity (“God dwells within you”).

Psychologically, this internalized connection functions as an ultimate secure attachment figure, fostering an internal locus of meaning and emotional regulation. Individuals who maintain high levels of internalized spiritual closeness exhibit lower existential threat reactivity, greater affective equanimity, and a persistent capacity to experience peace and self-transcending love, even amid profound physical illness or psychological duress.

6. Theoretical Framework

The INSPIRIT draws upon foundational perspectives in transpersonal psychology, the psychology of religion, and mind-body medicine. Its theoretical architecture reflects key contributions from several major thinkers:

William James: Primary vs. Secondary Religion

In his classic work, The Varieties of Religious Experience (1902), William James established a clear distinction between institutional religion (ecclesiastical structures, liturgical rituals, theology, and dogmatic creeds) and personal religion (the direct, immediate inner experiences of individuals in their solitude, feeling united with whatever they consider divine). James posited that institutional religion is merely secondary, derived from the foundational, primary mystical experiences of religious originators. The INSPIRIT is rooted in this Jamesian tradition: it explicitly bypasses denominational and institutional markers to isolate the direct, primary phenomenological encounters that constitute authentic personal religion.

Gordon Allport: Intrinsic vs. Extrinsic Religious Orientation

Gordon Allport’s seminal theoretical paradigm (Allport & Ross, 1967) posited two opposing psychological orientations toward religion:

• Extrinsic Religiosity: An instrumental, utilitarian orientation where religion is used to obtain external benefits, such as social status, communal belonging, or psychological security (“persons use their religion”).
• Intrinsic Religiosity: An internalized, deeply meaningful master-motive where religion serves as an overarching interpretive framework through which all of life is experienced (“persons live their religion”).

The INSPIRIT was formulated to capture the experiential heart of intrinsic religiosity. Kass et al. hypothesized that intrinsic motivation is catalyzed, sustained, and revitalized by direct core spiritual experiences. Without such subjective events, intrinsic faith often remains a theoretical ideal rather than an embodied, lived reality.

Herbert Benson: The Relaxation Response and “Remembered Wellness”

Herbert Benson’s physiological research at Harvard Medical School (Benson, 1975) identified the Relaxation Response as an inducible physiological state characterized by decreased oxygen consumption, reduced sympathetic nervous system activity, decreased heart rate, and increased parasympathetic dominance. Benson discovered that when individuals couple contemplative meditation with deeply held spiritual or philosophical convictions, the therapeutic efficacy of the relaxation response is enhanced. This synergistic interaction, which Benson termed the “faith factor” and “remembered wellness,” suggests that core spiritual experiences trigger powerful neurochemical cascades that diminish stress-induced bodily dysfunction. The INSPIRIT provided the explicit measurement vehicle necessary to test this mind-body connection in clinical health research.

Abraham Maslow: Peak Experiences

Abraham Maslow’s (Maslow, 1964) concept of peak experiences—moments of highest happiness, fulfillment, unitive consciousness, and perceptual clarity—provides another theoretical anchor. Maslow maintained that peak experiences are naturalistic, non-pathological, self-transcending states that foster psychological maturity and self-actualization. The checklist items in INSPIRIT Item 7 (e.g., profound inner peace, complete joy and ecstasy, unitive connection with the earth) operationalize the key emotional and cognitive markers of Maslowian peak experiences.

7. Validity

Extensive psychometric investigations have supported the construct, convergent, discriminant, and predictive validity of the INSPIRIT across clinical, outpatient, and general adult populations.

Construct Validity: Known-Groups Differentiation

Kass et al. (1991) established construct validity by demonstrating the scale’s ability to differentiate between groups with predictable differences in spiritual engagement. Based on transpersonal and meditative literature indicating that regular contemplative practice facilitates mystical states of consciousness, the authors hypothesized that experienced meditators would score significantly higher on the INSPIRIT than novice practitioners. In an outpatient behavioral medicine sample, participants with more than one month of consistent meditative experience achieved significantly higher INSPIRIT mean scores (M = 3.15, SD = 0.70) than individuals with less than one month of meditative practice (M = 2.70, SD = 0.85; t = 2.08, p < .04). This confirmed the instrument’s sensitivity to experiential spiritual practices.

Convergent Validity

Convergent validity has been evaluated against established indices of religious motivation and spirituality:

• Allport & Ross Religious Orientation Inventory (ROI): In the original validation study, INSPIRIT scores exhibited a robust, statistically significant positive correlation with the ROI Intrinsic Scale (r = .69, p < .0001), corroborating the theoretical premise that core spiritual experiences represent an experiential foundation for intrinsic religious commitment.
• Intrinsic Religious Motivation Scale (IRMS): In an independent validation study by VandeCreek, Ayres, and Bassham (1995) comprising 371 hospital-based outpatients and family members, the INSPIRIT demonstrated substantial positive correlations with Hoge’s (1972) Intrinsic Religious Motivation Scale (r = .61 using Kass’s scoring; r = .54 using VandeCreek’s cumulative scoring), confirming consistent construct measurement across diverse health care environments.

Discriminant Validity

Evidence for discriminant validity was demonstrated through the scale’s divergent relationship with the ROI Extrinsic Scale. Whereas the Intrinsic Scale correlated positively at r = .69, the Extrinsic Scale demonstrated a negative correlation approaching statistical significance (r = -.26, p < .06; Kass et al., 1991). This confirms that the INSPIRIT does not measure utilitarian, conformity-driven, or superficial religious posturing.

Predictive and Criterion Validity: Clinical Health Outcomes

In behavioral medicine cohorts, higher INSPIRIT scores have reliably predicted significant reductions in medical symptoms, lower frequency of healthcare utilization, reduced state anxiety, and elevated psychological resilience. Kass et al. (1991) observed that higher scores on the INSPIRIT were positively associated with greater life purpose and satisfaction, while buffered against negative affective responses to chronic physical symptoms. Similarly, in oncology and palliative care samples, higher INSPIRIT scores have correlated significantly with lower existential distress and elevated perceived quality of life.

8. Reliability

The INSPIRIT demonstrates high internal consistency and measurement precision across varying demographic and medical cohorts.

Internal Consistency

• Initial Validation Sample: In the original study of 83 behavioral medicine outpatients presenting with hypertension, cancer, chronic pain, and musculoskeletal disorders, Kass et al. (1991) reported an overall Cronbach’s coefficient alpha of .90. Item-total correlations across the seven items ranged between .69 and .85, demonstrating high internal cohesion without excessive item redundancy.
• Independent Health Care Cross-Validation: In the expanded clinical study by VandeCreek, Ayres, and Bassham (1995) involving 247 cancer outpatients and 124 surgical waiting-room family members (N = 371), internal consistency remained strong, yielding an overall Cronbach’s alpha of .88 across the full set of items and checklist components.

Stability and Test-Retest Properties

Because the INSPIRIT measures both lifetime transformative occurrences (which, once experienced, represent permanent autobiographical milestones) and stable attitudes regarding perceived divine closeness, the instrument exhibits substantial longitudinal stability. Short-term test-retest assessments over two- to four-week intervals in stable outpatient populations have demonstrated reliability coefficients exceeding r = .85. Minor fluctuations in longitudinal scoring typically reflect changes in state-level perceived closeness to God or the emergence of newly integrated spiritual experiences following acute contemplative or medical crises.

9. Factor Analysis

The structural dimensionality of the INSPIRIT was established through empirical factor analysis during the scale’s initial development and subsequently evaluated in independent replication studies.

Initial Item Pool Extraction

The original exploratory item pool comprised 11 candidate questions, incorporating items adapted from the National Opinion Research Center (NORC) General Social Surveys (Davis & Smith, 1985; Greeley, 1974) and newly authored questions by Kass et al. (1991). Principal components analysis (PCA) with orthogonal varimax rotation yielded three distinct factors:

• Factor 1 (Core Factor): Contained Items 1 through 7, displaying an eigenvalue of 4.58 and accounting for the majority of common variance.
• Factor 2: Contained Items 9 and 10, with an eigenvalue of 1.96.
• Factor 3: Contained Items 8 and 11, with an eigenvalue of 1.29.

Because Items 8 through 11 failed to form a unified, theoretically coherent construct and exhibited a significant drop-off in scree plot eigenvalue magnitude, they were eliminated. Items 1 through 7 were retained because they cleanly operationalized the two essential dimensions of core spiritual experiences.

Final Factor Structure

A subsequent unrotated principal components analysis conducted on the final 7-item scale revealed a clean, robust single-factor solution:

• Eigenvalue: 4.42
• Variance Explained: 63.1% of the total variance was accounted for by this single general factor.
• Factor Loadings: Every individual item demonstrated substantial factor loadings on this central dimension, ranging from .69 to .85:

The Item 7 Structural Controversy: Kass vs. VandeCreek

A methodological divergence emerged regarding the internal psychometric treatment of Item 7:

• Kass et al. (1991) Model: Item 7 is treated as a unified, single item. The overall question is scored based on the highest score recorded across any of the 12 experiential sub-types. The rationale is that a single profoundly transformative experience that solidifies conviction of God’s existence (score of 4) is sufficient to categorize an individual as having experienced a core spiritual event, regardless of whether they have had multiple different experiential varieties.
• VandeCreek et al. (1995) Model: These researchers argued that Kass’s approach discards critical clinical data regarding the cumulative breadth of spiritual phenomena. When VandeCreek et al. conducted a two-factor extraction treating all 12 checklist sub-items as independent variables alongside Items 1–6, they identified:

1. Factor 1 (General Spiritual Practices and Closeness): Accounted for 34.0% of the variance, with item loadings ranging from .52 to .68.
2. Factor 2 (Specific Spiritual / Mystical Occurrences): Accounted for 8.4% of the variance, with sub-item loadings ranging from .65 to .79.

While VandeCreek’s method captures cumulative experiential volume, comparative correlation studies with intrinsic religious motivation scales indicate that Kass’s original scoring yields higher convergent validity coefficients (r = .61 vs. .54). This suggests that the cognitive depth of an experience exerts a more definitive impact on intrinsic religiosity than the sheer quantity of disparate experiences.

10. Instrument / Measurement Tool

• Name: Index of Core Spiritual Experiences (INSPIRIT)
• Authoring Body: Mind/Body Medical Institute, Harvard Medical School / New England Deaconess Hospital (Jared D. Kass et al., 1991)
• Target Population: Adults and adolescents; validated across healthy, psychiatric, and medically ill populations (including chronic pain, cardiovascular, and oncology patients)
• Administration Type: Paper-and-pencil or computerized self-report questionnaire
• Administration Time: Approximately 3 to 5 minutes
• Format & Composition:
  • 7 primary items.
  • Items 1, 2, and 4 adapted from the National Opinion Research Center (NORC).
  • Item 3 adapted from NORC and Greeley (1974).
  • Items 5, 6, and 7 developed by Kass et al. (1991).
  • Item 7 incorporates a structured checklist of 12 distinct spiritual/mystical phenomena, plus an open-ended “Other” category.
• Response Scales:
  • Items 1–4: 4-point ordinal scales with item-specific behavioral and subjective response anchors. (Note: “Can’t answer” options are treated as missing data or scored neutrally per research protocol).
  • Item 5: Dichotomous cognitive appraisal query (Yes = 4, No = 1).
  • Item 6: 4-point Likert scale (1 = Definitely disagree to 4 = Definitely agree).
  • Item 7 Checklist: 4-point impact scale evaluating each experience’s effect on belief in God:
    • 1 = I have never had this experience
    • 2 = Did not strengthen belief in God
    • 3 = Strengthened belief in God
    • 4 = Convinced me of God’s existence
• Scoring Procedure:
  • Standard (Kass) Method: Item 7 is assigned a single score equal to the highest rating recorded among its 12 sub-types (range: 1 to 4). The total INSPIRIT composite score is calculated as the unweighted mathematical mean of all 7 items:
    
    Total INSPIRIT Score = (∑ Items 1 to 7) / 7
  • Score Range: 1.00 to 4.00.
  • Interpretation:
    • Scores 1.00 – 2.49: Low occurrence of core spiritual experiences; limited subjective closeness to the divine.
    • Scores 2.50 – 3.49: Moderate spiritual orientation and occasional spiritual experiences without absolute cognitive certitude.
    • Scores 3.50 – 4.00: Strong, unequivocal indication of the occurrence of at least one core spiritual experience, high internalized divine closeness, and high intrinsic spiritual motivation.

11. Permissions & Fee and Test Year

The INSPIRIT was originally published in 1991 in the Journal for the Scientific Study of Religion (Volume 30, Issue 2, pages 203–211). The copyright for the original article is held by the Society for the Scientific Study of Religion (published by John Wiley & Sons, Inc.).

For academic, clinical, and non-commercial research purposes, the INSPIRIT is generally accessible for use under standard academic fair-use guidelines, provided appropriate scholarly attribution and citation are given to Kass et al. (1991). Commercial applications, automated electronic health record integrations, or proprietary distributions require formal copyright clearance and licensing permissions through the copyright holder or the primary author (Dr. Jared D. Kass, Lesley University). No standard administrative fee is required for individual academic investigators.

12. References

Allport, G. W., & Ross, J. M. (1967). Personal religious orientation and prejudice. Journal of Personality and Social Psychology, 5(4), 432–443. https://doi.org/10.1037/h0021212

Benson, H. (1975). The Relaxation Response. William Morrow and Company.

Davidson, J. (1976). The physiology of meditation and mystical states of consciousness. Perspectives in Biology and Medicine, 19(3), 345–379. https://doi.org/10.1353/pbm.1976.0042

Davis, J. A., & Smith, T. W. (1985). General Social Surveys: 1972–1985. National Opinion Research Center.

Greeley, A. M. (1974). Ecstasy: A Way of Knowing. Prentice-Hall.

Hoge, D. R. (1972). A validated intrinsic religious motivation scale. Journal for the Scientific Study of Religion, 11(4), 369–376. https://doi.org/10.2307/1384677

James, W. (1902). The Varieties of Religious Experience: A Study in Human Nature. Longmans, Green, and Co. https://doi.org/10.1037/10004-000

Kass, J. D., Friedman, R., Leserman, J., Zuttermeister, P. C., & Benson, H. (1991). Health outcomes and a new index of spiritual experience. Journal for the Scientific Study of Religion, 30(2), 203–211. https://doi.org/10.2307/1387214

Kornfield, J. (1979). Intensive insight meditation: A phenomenological study. The Journal of Transpersonal Psychology, 11(1), 41–58.

Maslow, A. H. (1964). Religions, Values, and Peak-Experiences. Ohio State University Press.

VandeCreek, L., Ayres, S., & Bassham, M. (1995). Using the INSPIRIT to conduct spiritual assessments. Journal of Pastoral Care, 49(1), 83–89. https://doi.org/10.1177/002234099504900110

Walsh, R. (1978). Initial meditative experiences: Part I. Journal of Transpersonal Psychology, 9(2), 151–192.

13. Items of the Scale (Questionnaire)