Reliability and vailidity of the Japanese Version of the Acceptance and Action Questionnaire-3

Psychological flexibility is a core process in Acceptance and Commitment Therapy (ACT; Hayes et al., 2012) and is associated with higher well-being and lower levels of various psychological and behavioral problems. Its opposite process, psychological inflexibility, has traditionally been measured by the Acceptance and Action Questionnaire-II (AAQ-II; Bond et al., 2011). However, in recent years, criticisms regarding the psychometric properties of the AAQ-II have emerged, leading to its detailed examination and the development of revised versions (e.g., Fang et al., 2023; Ong et al., 2020; Ruiz et al., 2024). The current latest version is the AAQ-3. While English and Chinese versions have been developed, a Japanese version has not yet been created. Given the critiques regarding the proliferation of constructs and measurement scales in psychology (Anvari et al., 2025), the continuous revision of existing scales is preferable to creating new ones. Therefore, the purpose of this study is to develop a Japanese version of the AAQ-3 and to examine its psychometric properties.