Research on the satisfaction of the basic psychological needs for autonomy, competence, and relatedness is well-established in second language (L2) research. However, little is known about the frustration of these basic psychological needs and how they can undermine intrinsic motivation and L2 achievement. Importantly, there is no valid scale of the frustration of the basic psychological needs in the L2 context. Accordingly, the present study introduces a new scale called the Basic Psychological Needs Frustration in Second Language (BPNF-L2) and assesses its factor structure and criterion-related validity through the application of bifactor exploratory structural equation modeling (bifactor ESEM). Our results showed that scores obtained on the BPNF-L2 scale are reliable and valid. Moreover, our results support the criterion-related validity of this factor structure by showing that the general factor of BPNF-L2 negatively explains intrinsic motivation and L2 achievement while the BPNF-L2 specific factors (i.e., autonomy, competence, and relatedness frustration) explain the outcomes differently. The results indicate that feeling frustrated because basic psychological needs are not met may hinder the enjoyment and acquisition of the L2. Educational implications, methodological advancements, and directions for future research are provided.
