胖负面身体自我女性对不同效价身体信息的认知偏向:一项ERP研究

Cognitive Bias toward Body-Related Information of Different Emotional Valence among Females with Fat Negative Physical Self:An Event-Related Potential Study

采用改编后的1-back任务并结合ERPs技术考察胖负面身体自我女性对不同效价身体信息的认知偏向及其时间进程,结果发现:(1)身体词比非身体中性词诱发更大的P2和LPP波幅以及更小的N300波幅;(2)瘦积极、瘦消极词比胖积极、胖消极词诱发更大的LPP波幅。结果表明,女性在早期加工阶段区分了身体与非身体信息,在晚期加工阶段对瘦信息投入更多的认知资源,对瘦信息的注意维持增强,且晚期对身体信息的认知偏向是由体形维度主导而非情绪效价。

Considering the prevalence and serious consequences of weight dissatisfaction,investigation of the cognitive and neural mechanisms of weight dissatisfaction seems to have important social implications.According to Vitousek and Hollon’s(1990)cognitive theory of eating disorders,stereotyped,emotional,and exaggerated evaluations of weight-related information lead to maladaptive schemas related to body shape,weight,and the self.People with maladaptive schemas show an enhancement in attention and memory for schema-consistent information(e.g.,fat stimuli)and selectively resist schema-inconsistent information(e.g.,thin stimuli).At present,although previous studies have confirmed that people with fat negative body self show cognitive bias toward body-related information,there is still a lack of empirical research on the processing characteristics and neural mechanism toward body-related information of different emotional valence.In this experiment,participants were assigned to an experimental group with high weight dissatisfaction(HWD)and a control group with low weight dissatisfaction(LWD)according to the scores on the Negative Physical Self Scale-Fatness.The final sample included 40 female college students.We employed a modified 1-back task and recorded ERPs time-locked to visually present body-related words,including negative fat words,positive fat words,negative thin words,and positive thin words.The participants were requested to judge whether the current word was the same as the last one.Compared with the passive viewing and dot-probe paradigm,the 1-back task required participants to pay attention to each word,and after reducing the continuous repetition probability of the word,more analyzable trials could be reserved,and the fatigue effect of the participants could be alleviated to some extent.The behavioral results showed that the average accuracy for each group in the current study was over 95%,indicating that participants could complete the task efficiently.There was no significant difference in response time between the HWD and LWD groups.The ERP results showed that body-related words did not elicit larger anterior N1 and N170 amplitudes in the HWD group than in the LWD group,showing that there was no negative cognitive bias toward fatness-related information in the early ERP components related to attentional processing and cognitive resource investment among females with HWD.Besides,in both the HWD group and LWD group,body-related words induced larger P2 and LPP amplitudes and smaller N300 amplitudes than did non-body-related neutral words,additionally,positive thin words and negative thin words induced larger LPP amplitudes than did positive fat words and negative fat words.Since there were significant differences in LPP amplitude induced by different bodyrelated words,the average LPP amplitudes were analyzed by four-factor ANOVA to further distinguish the processing differences between body shape dimensions(fat and thin)and emotional valence(positive and negative).The results showed that cognitive bias toward body-related words was dominated by body dimensions rather than emotional valence in the late processing stage,and the LPP amplitude induced by thinness-related words was significantly higher than that induced by fatness-related words.In conclusion,the present study partially validates the cognitive-behavioral theory.Specifically,in the early processing stage,females could distinguish between body-related and non-body-related information,both fatness-related and thinness-related information were emotionally salient,and under the influence of task demand,the processing of body-related information was suppressed subsequently.In the late processing stage,females invested more cognitive resources toward thinness-related information and maintained more attention to thinness-related information.And the most important finding was that the females’cognitive bias toward body-related information in late processing was dominated by body shape rather than emotional valence.These findings reveal the mechanism of cognitive bias toward body-related information among females with fat negative body self and contribute to the model of the cognitive-behavioral theory of body image disturbance,which may help enhance prevention and interventions for reducing weight dissatisfaction.