The OESQ is a brief, state-related self-report process measure of psychological flexibility.
References:
Benoy, C., Knitter, B., Knellwolf, L., Doering, S., Klotsche, J., & Gloster, A.T. (2019) Assessing psychological flexibility: Validation of the Open and Engaged State Questionnaire. Journal of Contextual Behavioral Science, 12, 253-260. https://doi.org/10.1016/j.jcbs.2018.08.005
Rogge, R.D., Daks, J.S., Dubler, B.A., & Saint, K.J. (2019) It's all about the process: Examining the convergent validity, conceptual coverage, unique predictive validity, and clinical utility of ACT process measures. Journal of Contextual Behavioral Science, 14, 90-102. https://doi.org/10.1016/j.jcbs.2019.10.001