Exploring scale validity and measurement invariance of the Toronto Mindfulness Scale across levels of meditation experience and proficienc

Objectives: The Toronto Mindfulness Scale (TMS) is a widely used instrument of state mindfulness. Research suggests the interpretation and functioning of mindfulness scale items may differ as a function of meditation experience, and thus, establishing invariance across experience levels is essential. Methods: Five hundred and five meditation practitioners (32.7% male, 33.3% female, and 34.1% unspecified) with an average age of 42.37 years (SD?=?12.70) completed the TMS online. Results: Results support at least partial invariance across subgroups based on years of mindfulness meditation experience and self-reported proficiency. Construct validity of the Decentering subscale was also supported; however, the Curiosity subscale did not meet validity expectations, as it required additional model modifications to yield good fit, and means were not sensitive to differences in group experience or proficiency. Conclusions: Our findings suggest further review of the TMS Curiosity items may be warranted to determine its suitability for use within mindfulness assessment