We have presented population standardized data of the Freiburg Mindfulness Inventory (FMI) in its short version with 14 items and psychometric data that support the use of a shorter 13 item version FMI-13R, where the only reversed item has been removed. The scale is psychometrically sound. It has one general factor, which can be disentangled for conceptual purposes into two highly correlated factors of Presence and Acceptance. The latter is useful, because it turns out that these conceptual facets explain relationships of the construct with depression, anxiety and physical symptoms: while the acceptance component correlates negatively, the presence component correlates positively, if the other is controlled for in a partial correlation analysis. A CFA supports this distinction into two facets with a reasonably good fit. A regression analysis supports the validity of the instrument: the mindfulness score is higher in those participants who practice more and who are older. However, paradoxical effects can also be seen: practitioners with a very regular practice tend to report lower scores. This is likely a response shift phenomenon. Response shift is a bias where those who are very diligent in their practice become more critical of their state of mindfulness [63].
We have confirmed that the original item 13, which is the only negatively worded item (and has to be recoded to “I am impatient with myself and others”) is, psychometrically spoken, an outlier. Hence, we recommend using the version of the scale that is reduced by that item and thus contains only 13 items, the FMI-13R.
The model performance values in the present study are generally somewhat lower than in other studies such as those by [33, 35, 50, 58, 64].This has very likely to do with the fact that we have an unselected sample representative of the German population, while most mindfulness studies attract persons with some affinity to the concept of mindfulness and/or spirituality. This increases variance and reduces the goodness of fit of models. Hence, the results of this study may provide a more robust and more realistic picture compared to many other studies.
Our analysis confirms that mindfulness is a global construct, which can, for purposes of clarification or for conceptual issues, be separated into highly correlated sub-constructs, Presence, and Acceptance. Over and above, previous research reached similar conclusions as to the factorial structure [35, 58]. This result regarding the factor structure of the FMI has also some pragmatic consequences. Our findings suggest that the Acceptance facet is more important for clinical effects, such as reduced anxiety or depression, but that in order to grow acceptance, a practice of presence is useful [36]. In a similar vein, a recent study reports that acceptance, and not presence, increases psychological well-being [4], thus corroborating our finding. As this is the result of interpreting our cross-sectional data, this needs to be supported by longitudinal studies that can map the temporal development of practitioners. It should be noted that other self-assessment scales of mindfulness tend to conceptualize subfactors similar to “presence” and “acceptance”, too [65–68]. An exception is the Langer Mindfulness Scale [65, 69–71], where mindfulness is defined as an attitude of openness to novelty in which the individual draws novel distinctions, i.e., constructs her or his own categories.
Our factorial analysis arrives at a slightly different allocation of items to constructs than our previous analysis (Supplementary Table S2) [35]. We have also analyzed this previous allocation of items to constructs and obtained a satisfactory fit with these data. Depending on the sample, a model fit of a confirmatory model supports either allocation of items to constructs. We have chosen here to report the previous allocation of items to constructs, because the model fit statistics allow this even for the general sample. So, depending on which kind of individuals or sample are measured, with our without spiritual practice, practitioners may feel free to use either model, if they want to investigate sub-domains of the global mindfulness construct.
While the factorial structure remains, over and above, the same compared to previous studies, the question why there are some differences in the factor structure found, can be answered by the fact that we have used a general, representative sample. If this is used, a slightly different item-allocation ensues. The previously found structure is useful for a sample or individuals with spiritual practice.
Compared to the vast majority of similar studies, we built on a general-population representative study. In contrast, many other studies tap into convenience samples or samples of mindfulness practitioners. In this light, it seems plausible that results might differ somewhat thereby reflecting the (slightly) diverging mental constructs of the participants. However, it seems reassuring to us that the factorial structures are similar to a large extent. As this analysis is derived from a general population sample, it is likely more representative and robust.
One might argue that a variety of widely and empirically well backed-up used instruments for measuring mindfulness exists, such as and probably foremost, the Five Facets Mindfulness Questionnaire [72–75]. While it is true, we think that the present study fills a gap, as there is a paucity of studies built on representative samples, and not convenience samples of patients, students or practitioners. To reiterate, we readily agree that several instruments exhibit supportive evidence, but we think the field would benefit from more research drawing not from adhoc samples but from representative samples allowing gauging individual results.
One might argue against the usage of any questionnaire to assess mindfulness [21]. For example, a recent study advocates breath counting as a measure of mindfulness [22]. One further behavioral alternative to self-assessment, perceptual stability in perceiving the Necker Cube, has been elaborated on earlier [76]. While we would in principle agree that self-reports are not a good means of assessing mindfulness, it is still quite pragmatic and well backed-up by empirical evidence as reported by several reviews [19, 20, 65]. Ideally, one would have various and multi-level-analyses methods, such as observation of actions and daily practice in addition to self-report. This is the traditional testing mode in, for instance spiritual traditions using breath awareness such as Zen and Vipassana practice [22, 77]. However, it might only useful in personal encounters and contexts where personal spiritual growth is in the focus. For such purposes we would not advocate, at least for the time being, the usage of a questionnaire instruments, ours or anybody else’s, at any rate.
But if, for instance, a practitioner wants to get an overview over various personality components in a client, or if researchers want to assess progress of participants in a mindfulness training program, questionnaires are still a parsimonious method of collecting data. It was in this spirit that we conducted this study and present population norm data.
Whereas the main objective of the present study is to provide norm values and robust statistics due to the representative sample, our results shed some light to potential pathways (or mediators) of mindfulness. Of remark, while authors continue to publish studies investigating the effects of mindfulness and the instruments for measuring mindfulness, much less effort has been put into the understanding of how mindfulness conveys its effects [but see 78, 79–82]. As stated above, our results suggest that acceptance rather than presence mediates the beneficial effects of mindfulness practice. On this ground, we hypothesize that accepting negatively valanced experiences is a direct cause of alleviating health conditions; presence rather serves as a means of building up acceptance. Future intervention development efforts can investigate whether the individual capacity of acceptance is a vehicle of health. This finding may provide the creators of mindfulness interventions with opportunities for novel approaches or at least with more confidence to continue their research endeavors. Mindfulness training appears to be one avenue for increasing acceptance, which in turn conveys health-related benefits. Other avenues for building up acceptance such as neurofeedback might exist and should be investigated.
The strength of this study is the fact that we used an approximation to the German population by employing a professional response panel and approximating the most important sociodemographic parameters of the German population. Thus, there is no positive selection bias due to affinity to meditation, mindfulness or other spiritual practices. This also resulted in a comparatively large sample of more than 1.000 participants. We thus are able to report population standardized scores which should allow researchers and practitioners to use the instrument also for assessment purposes, where mindfulness is to be assessed, for instance for purposes of comparison, or for the assessment of development.
Limitations and future Research
A word of caution is due: Every self-assessment instrument is prone to a social desirability bias [83, 84]. Indirect hints that this might be a problem can be seen in our regression analysis: whoever has theoretical knowledge of mindfulness has in tendency a higher score. Also, practitioners with more practice and experience tend to score lower, likely because they assess themselves more critically. This effect is well-known and has been dubbed the Dunning-Kruger Effect [59]. These are some of the limitations of such instruments. If this limitation is kept in mind, one would use scores derived from such instruments diligently, i.e. not in an absolute and definitive way, but as an indicator which might be most useful if assessed in comparison to other indicators or in its temporal sequence.
It might be useful to explore in future studies, how the two components, Presence and Acceptance, are related in their temporal development and how they relate to other relevant constructs. In addition, the field is likely to benefit from more studies drawing on representative, or at least diverse samples such as the sample of the present study. Seen from a broader perspective, a clearer understanding of the causal mechanisms of mindfulness will, reversely, support the improvement of measurement. To the extent that we know what mindfulness “does” to body and mind, we are able to measure those effects. In particular, presence and acceptance may be susceptible to behavioral and/or physiological measurement. For example, a recent study investigated experience-sampling in the context of breathing concentration exercise as behavioral means for measuring mindfulness [22]. Relatedly, perceptual stability of ambiguate images may prove to serve as a behavioral measurement of mindfulness [76]. Furthermore, our results suggest that acceptance as a mediator of change is a worthwhile candidate of research efforts, in line with existing evidence [56, 82, 85]. We suggest that future studies continue to elaborate this direction.
We conclude that the Freiburg Mindfulness Inventory (FMI-13R) in its newly presented 13-item version is a psychometrically sound instrument to assess self-attributed mindfulness. It can be used as a short-term state assessment, or a longer term trait assessment, depending on the time frame indicated on the questionnaire when presenting it. Although it assesses a general factor, this factor can be disentangled in two highly correlated conceptual components, Presence and Acceptance. For this differentiation there is not only some statistical support from a CFA, but also from partial correlations. The population standardized data reported here can be used to put findings with the instrument into context.