保护行为可以有效减少校园欺凌事件并降低校园欺凌带来的不良结果。促进保护行为是当今各国共同关注的主题，探究哪些因素会影响保护行为尤为重要。保护者做出保护行为前会对情境中的风险与收益进行评估，情境中的风险和收益对保护行为的发出起重要作用。一方面，保护者做出保护行为会使自己面临受欺凌风险（言语上、关系上、身体上）；另一方面，保护行为也会获得被保护者的积极反馈，从而带来人际收益。本研究考察保护者做出保护行为的风险对保护行为的影响，以及被保护者感恩表达的作用机制。

研究一采用交叉滞后分析，探索保护行为与三种受欺凌形式（言语受欺凌、关系受欺凌、身体受欺凌）的关系。使用问卷法对我国北部某初中7、8年级24个班级的学生进行3次调查，第一波数据（T1）收集时间为7、8年级春学期初，第二波数据（T2）收集时间为7、8 年级春学期末，第三波数据（T3）收集时间为8、9年级秋学期末。最终被试为424名保护者（非欺凌者与受欺凌者）（M年龄 = 13.67，SD = 0.822，男生 46.5%）。结果显示，（1）青少年 7、8 年级春学期初的保护行为显著正向预测 7、8 年级春学期末的关系受欺凌及身体受欺凌，7、8年级春学期末的保护行为显著正向预测 8、9 年级秋学期末的言语受欺凌；（2）青少年 7、8 年级春学期末的身体受欺凌显著正向预测 8、9 年级秋学期末的保护行为。

研究二通过实验探究保护行为的风险对保护行为的影响，以及被保护者感恩表达的促进作用。具体而言，研究 2a 探究三种保护行为风险对保护行为的影响。被试为我国北部某初中8 年级的 71名学生（24 名女生，M 年龄 = 13.59，SD = 0.575），其中言语威胁组 28 人，社会排斥组 19 人，身体攻击组 24 人。数据分析采用 SPSS 26.0 和 Mplus 8.3。配对样本 t 检验及方差分析结果显示，（1）保护行为带来的三种受欺凌风险的严重程度之间不存在显著差异；（2）三种保护行为风险均会促进青少年的保护行为，且不同保护行为风险对于保护行为的促进作用之间没有显著差异。研究 2b 探究被保护者感恩表达的促进作用。被试为我国北部某初中 8 年级 155 名学生（71 名女生，M 年龄 = 13.74，SD = 0.650），每组人数在 23 到 30 人之间。配对样本 t 检验及重复测量方差分析的结果显示，（1）被保护者的感恩表达促进青少年的保护行为；（2）在言语威胁风险下，被保护者的中性表达和感恩表达对保护行为均没有显著影响；在社会排斥风险下，中性表达和感恩表达均促进保护行为；在身体攻击风险下，中性表达降低青少年的保护行为，感恩表达对保护行为没有显著影响。

本研究支持了保护行为是一种亲社会冒险行为的观点，发现青少年做出保护行为的确存在受欺凌风险；与超级利他主义视角的观点一致，发现受欺凌风险促进了保护行为的发生；验证了感恩表达的道德强化功能，发现被保护者的感恩表达对青少年的保护行为起促进作用；符合成本-收益模型及竞争性利他主义视角，发现青少年在不同的风险情境下，对作出保护行为带来的风险和收益的权衡存在差异，并最终影响保护行为的发出。总之，本研究为保护行为的风险-收益研究提供实证依据，为校园欺凌干预提供启示。

Defending behaviors can effectively reduce the occurrence of school bullying and mitigate the adverse outcomes associated with bullying. Promoting defending behaviors is a topic of common concern in various countries, and it is particularly important to explore the factors that influence defending behavior. Before engaging in defending behavior, defenders tend to evaluate the risks and benefits in the given situation. Thus, the risks and benefits in the context play a significant role in the initiation of defending behavior. Engaging in defending behavior exposes defenders to the risk of being bullied (verbally, relationally, or physically), but it also allows them to receive positive feedback from the individuals they defend, resulting in interpersonal benefits. The present study examined the effect of defenders’ risks of engaging in defending behaviors on defending behaviors and the mechanisms of the defended victims’ gratitude expression.

Study 1 employed cross-lagged analysis to explore the relationship between defending behaviors and three forms of victimization (verbal victimization, relational victimization, and physical victimization). A questionnaire survey was conducted with students from 24 classes in the 7th and 8th grades of a middle school in northern China. The first wave of data (T1) was collected at the beginning of the spring semester for the 7th and 8th grades, the second wave of data (T2) was collected at the end of the spring semester for the 7th and 8th grades, and the third wave of data (T3) was collected at the end of the fall semester for the 8th and 9th grades. The final sample consisted of 424 participants categorized as defenders (non-victims and victims) (46.5% males, Mage = 13.67, SD = 0.822). The results revealed that (1) defending behaviors at the beginning of the 7th and 8th grade spring semester significantly predicted relational victimization and physical victimization at the end of the 7th and 8th grade spring semester, and defending behaviors at the end of the 7th and 8th grade spring semester significantly predicted verbal victimization at the end the 8th and 9th grade fall semester; (2) physical victimization at the end of the 7th and 8th grade spring semester significantly positively predicted defending behaviors at the end the 8th and 9th grade fall semester.

Study 2 employed a behavioral experiment to investigate the influence of the risks of engaging in defending on actual defending behaviors and the facilitating role of defended victims’ gratitude expression. Specifically, Study 2a examined the impact of three types of victimization risks on defending behaviors. The participants were 71 students (24 females, Mage = 13.59, SD = 0.575) from the 8th grade of a middle school in northern China, including 28 in the verbal threat group, 19 in the social exclusion group, and 24 in the physical aggression group. Data analysis was conducted using SPSS 26.0 and Mplus 8.3. Results from paired-samples t-tests and analysis of variance (ANOVA) indicated that (1) there were no significant differences in the severity of the three forms of victimization risks posed by defending behaviors; (2) all three types of risks promoted defending behaviors among adolescents, with no significant differences in the facilitating effects of different defending behavior risks. Study 2b investigated the mechanism of gratitude expression by the defended victims. The participants were 155 students (71 females, Mage = 13.74, SD = 0.650) from the 8th grade of a middle school in northern China, with group sizes ranging from 23 to 30. Results from paired-samples t-tests and repeated measurement ANOVA revealed that (1) defended victims’ gratitude expression facilitated defenders’ defending behaviors; (2) under the risk of verbal threats, the defended victims’ neutral expression and gratitude expression had no significant impact on defending behaviors; under the risk of social exclusion, both neutral expression and gratitude expression promoted defending behaviors; under the risk of physical aggression, neutral expression decreased defenders’ defending behaviors, and gratitude expression had no significant impact on defending behaviors.

This study supported the perspective that defending behavior is a prosocial risky behavior by finding evidence of engaging in defending behaviors was positively associated with the risks of being bullied. Consistent with the perspective of extreme altruists, the study revealed that victimization risks facilitated the occurrence of defending behaviors. The study validated the moral reinforcement function of gratitude expression by demonstrating its promoting effect on adolescent defending behaviors among the defenders. In line with the cost-benefit model and the competitive altruism perspective, the study identified differences in the trade-off between risks and benefits when engaging in defending behaviors among adolescents in different risk contexts, and ultimately influencing the occurrence of defending behaviors. In conclusion, this study provided empirical evidence for the risk-benefit study of defending behaviors and provided insights into school bullying intervention.