Volunteering is an important symbol of social progress and plays a significant role in building a community for social governance. However, China currently faces challenges of low participation continuity and high volunteer attrition. Exploring the dynamics and mechanisms underlying sustained volunteering behavior is crucial for addressing these issues. Existing studies predominantly examine the one-way influence of volunteer motivation and role identity on sustained volunteering behavior from a static perspective, with limited focus on the dynamic relationships between variables over time. This static interpretation may be disconnected from real-life situations and fail to fully reflect the continuous nature of volunteering as a result of both individual factors and time. In fact, volunteer motivation and role identity evolve and change throughout the volunteering process. This change represents the cognitive construction and reconstruction that volunteers experience as they engage in sustained behaviors. Failing to consider this dynamic process can result in an incomplete understanding of the formation and continuity mechanisms of volunteer behavior, thereby limiting the effectiveness of strategies aimed at improving volunteer retention rates.

To explore the dynamic relationship between volunteer motivation, role identity, and sustained volunteering behaviors, this study employed a three-wave longitudinal design. The study followed 442 college student volunteers (M_age = 19.27 years, SD = 1.67 years, female 86.65%) three times over a one-year period (T1: March 2023, T2: September 2023, T3: March 2024). Data were analyzed using SPSS 27.0 and Mplus 8.3, and a cross-lagged panel model (CLPM) was constructed to test a reciprocal circular model between the three variables, with gender and age as covariates. Volunteer motivation was assessed using the Volunteer Functions Inventory, and role identity was measured with the Volunteer Role Identity 5-Item Scale. Sustained volunteering was measured by averaging the standardized scores for time spent on volunteering, volunteering frequency, and volunteers' intention to continue volunteering. All measurements had good reliability and validity, and there was no severe common method bias, ensuring the robustness of the study findings. The main variables involved exhibited a certain degree of stability over time, meeting the conditions required for establishing a cross-lagged model.

The study found that: (1) A reciprocal relationship existed between volunteer motivation and role identity. Volunteer motivation at T1 and T2 positively predicted role identity at T2 and T3 (β_T1=.13, p<.01; β_T2=.11, p<.05), and role identity at T1 and T2 positively predicted volunteer motivation at T2 and T3 (β_T1=.10, p<.05; β_T2=.12, p<.05). (2) Role identity and sustained volunteering also demonstrated a reciprocal relationship. Role identity at T1 and T2 positively predicted sustained volunteering at T2 and T3 (β_T1=.24, p<.001; β_T2=.17, p<.01), and sustained volunteering at T1 and T2 positively predicted role identity at T2 and T3 (β_T1=.16, p<.001; β_T2=.11, p<.05). (3) There was no significant direct effect between volunteer motivation and sustained volunteering; rather, their reciprocal relationship was established through role identity. Specifically, the mediating effect of T2 role identity between T1 volunteer motivation and T3 sustained volunteering was significant (β=.02, p<.05, 95%CI=[.00,.04]); Similarly, the mediating effect of T2 role identity between T1 sustained volunteering and T3 volunteer motivation was also significant (β=.02, p<.05, 95%CI=[.00,.04]).

Drawing upon the Triadic Reciprocal Determinism, Functionalism, and Motivated Identity Construction Theory, this study employs the CLPM to investigate the longitudinal reciprocal relationships among volunteer motivation, role identity, and sustained volunteering. The findings demonstrate that stimulating and fulfilling volunteer motivation serves as a critical starting point for promoting sustained participation in volunteer activities. Furthermore, role identity emerges as a pivotal factor in both maintaining and enhancing volunteer motivation and behavior, while also functioning as the core mechanism facilitating individuals' transition from short-term engagement to long-term commitment. These insights carry significant implications for developing effective strategies to foster sustained volunteer engagement and improve volunteer management practices.