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Research on the involvement of the cerebellum in social behavior and its relationship with social mentalizing has just begun. Social mentalizing is the ability to attribute mental states such as desires, intentions, and beliefs to others. This ability involves the use of social action sequences which are believed to be stored in the cerebellum. In order to better understand the neurobiology of social mentalizing, we applied cerebellar transcranial direct current stimulation (tDCS) on 23 healthy participants in the MRI scanner, immediately followed by measuring their brain activity during a task that required to generate the correct sequence of social actions involving false (i.e., outdated) and true beliefs, social routines and non-social (control) events. The results revealed that stimulation decreased task performance along with decreased brain activation in mentalizing areas, including the temporoparietal junction and the precuneus. This decrease was strongest for true belief sequences compared to the other sequences. These findings support the functional impact of the cerebellum on the mentalizing network and belief mentalizing, contributing to the understanding of the role of the cerebellum in social sequences.

Previous studies on social groups demonstrated processing differences related to the perceived level of group-entitativity. It was found that processing information from members of high entitative groups, as compared to members of low entitative groups, will lead to the formation of an abstract prototypical image of a group-member, which is subsequently transferred to the other group-members in an attempt to achieve increased efficiency in processing daily social reality. In the current study we examine the brain activation patterns associated with these differences in perceived levels of group entitativity. Twenty native Dutch-speaking participants read blocks of behavioral descriptions belonging to four protagonists who were part of either a high or a low entitative group. Prior to the presentation of each group, the type of group and assumed entitativity level were provided. The participants received behavioral information about 20 high entitative groups and 20 low entitative groups. The results revealed an adaptation effect for trait-inference, that is, the activation decreased as more behavioral information was read about group members. This effect was observed in the Anterior Cingulate, Middle Cingulate and Paracentral Lobule. Adaptation in the bilateral frontal gyri was related to the difference in perceived level of group entitativity, with adaptation being stronger for low as opposed to high entitative groups, suggesting that more trait-related learning took place for low entitative groups. The impact on current theories about group perception will be discussed during the presentation.

Recent findings indicate that processing trait-related information generates a different pattern of brain activation than the processing stereotype-related information. In this fMRI-study we explicitly compared the processing of both trait- and stereotype-related information. 18 participants judged the applicability of a description with respect to a trait or a stereotype prime. These behavioral sentences varied on both valence and consistency with regard to the prime. We predicted that judging the applicability of behaviors to stereotypes would increase activation in mentalizing brain areas more than judging the applicability of behaviors to personality traits, because stereotypes encompass a larger number of individuals with more variation and less communality than a single personality trait. Stated differently, stereotypes involve more associative links with individuals exemplary members of groups and situations in which they typically behave, and so lead to higher involvement ofthe mentalizing areas that connect all this information. As predicted, the results demonstrate that applicability judgments based on stereotypes activate mentalizing areas more strongly than those based on traits, including a large portion of the medial prefrontal cortex as well as the temporo-parietal junction and precuneus. This is about equally true for behavioral descriptions that are consistent or inconsistent with the judged trait or stereotype.

The traditional view on the cerebellum is that it controls motor behavior. Although recent work has revealed that the cerebellum supports also nonmotor functions such as cognition and affect, only during the last 5 years it has become evident that the cerebellum also plays an important social role. This role is evident in social cognition based on interpreting goal-directed actions through the movements of individuals (social "mirroring") which is very close to its original role in motor learning, as well as in social understanding of other individuals' mental state, such as their intentions, beliefs, past behaviors, future aspirations, and personality traits (social "mentalizing"). Most of this mentalizing role is supported by the posterior cerebellum (e.g., Crus I and II). The most dominant hypothesis is that the cerebellum assists in learning and understanding social action sequences, and so facilitates social cognition by supporting optimal predictions about imminent or future social interaction and cooperation. This consensus paper brings together experts from different fields to discuss recent efforts in understanding the role of the cerebellum in social cognition, and the understanding of social behaviors and mental states by others, its effect on clinical impairments such as cerebellar ataxia and autism spectrum disorder, and how the cerebellum can become a potential target for noninvasive brain stimulation as a therapeutic intervention. We report on the most recent empirical findings and techniques for understanding and manipulating cerebellar circuits in humans. Cerebellar circuitry appears now as a key structure to elucidate social interactions. Frank Van Overwalle, Elien Heleven, Qianying Ma, and Min Pu were supported by an SRP57 grant from the Vrije Universiteit Brussel, and Elien Heleven was additionally supported by an FWO G002319N/AL907 grant from the Flemish government. Zaira Cattaneo was supported by a Bando Ricerca Finalizzata (GR2016-02363640) by the Italian Ministry of Health. Marco Michelutti and Arseny A. Sokolov were supported by aMille E Una Lode fellowship from the University of Padua to MM, and fellowships from the Leenaards Foundation and the Swiss National Science Foundation, and a grant from the Helmut Horten Foundation to AAS. Catherine Stoodley and Laura C. Rice were supported by an NIH R15MH106957 grant. Van Overwalle, F (corresponding author), Vrije Univ Brussel, Dept Psychol, Pl Laan 2, B-1050 Brussels, Belgium; Vrije Univ Brussel, Ctr Neurosci, Pl Laan 2, B-1050 Brussels, Belgium. Frank.VanOverwalle@vub.ac.be; mmanto@ulb.ac.be; zaira.cattaneo@unimib.it; silvia.clausi@uniroma1.it; chiara.ferrari@unipv.it; gabrieli@mit.edu; xguellparadis@mgh.harvard.edu; Elien.Heleven@vub.be; m.lupo@hsantalucia.it; Qianying.Ma@vub.be; michelutti.marco.m@gmail.com; g.olivito@hsantalucia.it; Min.Pu@vub.be; laura.blevins@student.american.edu; jschmahmann@mgh.harvard.edu; libera.siciliano@uniroma1.it; Arseny.Sokolov@chuv.ch; stoodley@american.edu; kim.vandun@uhasselt.be; LVandervert@aol.com; maria.leggio@uniroma1.it