The Neural Mechanism Of The Stereotype Activation

As one of the most important topics in the social cognition research, stereotype refers to stabilizing beliefs toward certain groups. The characteristic of this psychological phenomenon significant reveal as an automatic social thinking as well as a social categorization function to social groups. With the emergence of the social cognitive neuroscience approach, the current stereotype and stereotyping research has deepened on their neural mechanisms. Recent research indicates that many brain regions are involved in the stereotyping processes, including attention system, sematic processing system, executive control system, and limbic system. Moreover, these attention, sematic and inhibition processes could be revealed by certain event-related potentials (ERPs).Basing on the social cognitive neuroscience research frame, the current study utilized ERP and fMRI techniques to explore the neural mechanisms of the sematic stereotype through two parts with a total of four experiments. Since previous research has showed that the stereotyoe activation mainly associated with the attention system and sematic system, we primarily inspected the processes of sematic stereotype in attentional and sematic processing. In the first part (including Experiment1and Experiment2), we inspected the attentional processes of sematic stereotype, and explored its association with the posterior attention net (PAN) and working memory of the attention system, In the second part (including Experiment3and Experiment4), we inspected the sematic processes of the sematic stereotype representation. Because previous research has revealed that the conscious and attention could moderate the long-term memory bases of the stereotype, in this part we conduct the conscious and attention as independent variable and explore the different neural bases of the implicit and explicit sematic stereotypes. The intention of the Experiment1was to investigate the association between the automatic stereotype activation and posterior attention net (PAN). In this experiment, a modified attentional cueing task was used to evoke the stereotype activation and the inhibition of return (IOR), and ERPs were used to identify their association. In this task, gender traits were used as priming cue. and the gender labels were used as target. In each trial, participants were asked to give response to the cue’s spatial location (right/left) but ignore the sematic information. The result found that the sematic stereotypes still affect the IOR, and this effect significantly revealed as the female stereotypical inconsistent semantics modified the attention shift processing of the IOR. Moreover, all those effect were showed by a posterior N2effect. However, this effect only appeared at the valid cue condition. Since the IOR was mainly processed by PAN, this experiment demonstrated that the sematic stereotypes could interact with the attentional process of the PAN. First, it could affect the IOR and evoke the attentional bias under given condition. But in other hand, this sematic stereotype activation in IOR situation might be still modulated by attention process.The intention of the Experiment2was to inspect the association between the automatic stereotype activation and the working memory system. In this experiment, a modified dual-target rapid serial visual presentation (RSVP) task was used to evoke the stereotype activation and the attentional blink (AB), and ERPs were used to identify their association. In this task, gender labels were used as T1, gender traits were used as T2, and names of fruit were employed as interference stimulus. In each trial, participants were asked to recognize the T1and T2in the rapid visual stream and then report them after the presentation. The behavioural result of this experiment showed significant main effects of stereotype and AB, as well as a significant interaction between them. While the ERP result further indicated that the stereotype process could be reflected on N2, P3and N400. and its interaction with AB happened on the working memory process indexed by P3stage. Considering the AB reflect a temporary lack of working memory consolidation in late attentional process, above results indicated that the automatic stereotype could impact the working memory process in late attentional process but do not rely on the working memory resource.The intention of the Experiment3was to exam the difference neural mechanism between the implicit and explicit stereotype by ERP technique, In this experiment, gender names and traits were used as stimuli, and an implicit Extrinsic Affective Simon Task (EAST) and an explicit sematic priming task were employed to evoke the implicit and explicit stereotypes respectively. Through comparing their neural processes reflected by ERPs. their different mechanisms were revealed. The results of experiment3found that the implicit and explicit stereotypes indeed have different mechanisms in processing. The implicit stereotype evoked in EAST appeared at late sematic processing stage, and mainly revealed as the separation effect on the trait evaluation component LPPa which appeared at the frontal-centre of the scalp. In contrast, the explicit stereotype evoked by the sematic priming task may have two processing stage, respectively revealed as the per-lexical processing indexed by frontal N2and the late trait evaluation processing indexed by posterior LPPb component. Although those two LPP effect have different scalp distributions, their difference waves were both located at the fontal scalp. This result indicated that the prefrontal cortex may involve both in the implicit and explicit stereotyping process, revealing a similarity between them.The intention of the Experiment4was to explore the different neural bases of the implicit and explicit stereotypes basing on the results of the experiment3. In this experiment, fMRI technique was employed and tasks in experiment3were modified to suit for the MRI scanning. The results of the experiment4showed that the implicit and explicit stereotypes indeed have different neural cortex bases. The separate analysis on the EAST indicated that the rostral anterior cingulate (rACC) and superior frontal gyri (SFG) were engaged in the processing of the implicit stereotype activation, while the inferior frontal gyri (IFG) and ventral anterior cingulate (vACC) engaged in the stereotype inhibition processes. For the separate analysis on sematic priming task, however, SFG and IFG were engaged in explicit stereotype activation, but cerebellum and inferior parietal were engaged in explicit stereotype inhibition processes. Finally, the direct task comparison revealed that the implicit stereotyping processes were much more rely on the implicit sematic conceptual priming system, while the explicit stereotyping processing may be much more depend on the explicit sematic conceptual system and the motivation system.The conclusions of the whole study could be sum up as following:(1) the processes of the sematic stereotype are complex but flexible, and distributed neural networks or systems might contribute to its different facets. In different condition, the activation of the sematic stereotype could affect the attentional coding and evoke attentional bias, also could impact the late evaluation and sematic perception processes. (2) The sematic stereotyping could impact the on-line searching process of the working memory system, but do not depend on its limited resource.(3) The sematic stereotype has at least two representation systems; one is the implicit representation system and the other is the explicit representation system. Those two systems have different neural bases, but both of them associate with the prefrontal cortex. These flexible representation systems might be the important reason account for the "enlighten gestalt" role of sematic stereotype in the social perceptions.