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Description: Difficulties in everyday social interactions and communication are one of the hallmarks of autism spectrum disorder (ASD; American Psychiatric Association, 2013). One of the leading hypotheses about the causes of these social communicative difficulties is a deficit in theory of mind (ToM) or mentalizing (Baron-Cohen et al., 1985). ToM is defined as the ability to represent mental states of ourselves and others. Inferring other people’s beliefs and thoughts is crucial for having a conversation with someone as well as interacting with other people more broadly. Most of the tasks that claim to target ToM have shown that they elicit activity in a core network of brain regions, which comprises the bilateral posterior temporoparietal junction (TPJ) and the medial prefrontal cortex (mPFC; Schurz et al., 2014). Many tasks have been developed to assess ToM abilities. Not all of these tasks, however, target ToM specifically. For example, performance on the Reading the Mind in the Eyes task (Baron-Cohen, Wheelwright, Hill, et al., 2001) can be attributed to alexithymia, and not ToM (Oakley et al., 2016). Another potential drawback of most tasks is that they rely on explicit mentalizing, which means that participants are asked to verbally describe or categorize the beliefs or thoughts of others (among others Frith-Happé animations; Castelli et al., 2002; False Belief; Fletcher et al., 1995). This contrasts with real-life use of ToM, for instance in communication, where interlocutors most often represent the beliefs of others without being asked to report about them. Interestingly, autistic people perform on the same level as neurotypicals on explicit mentalizing tasks, but make less use of implicit sources of information on the beliefs of another person, such as eye gaze (Baez & Ibanez, 2014; Schilbach et al., 2006; Senju et al., 2009). For these reasons, an implicit ToM task would correspond more closely to mentalizing in everyday situations. In addition to the reliance on explicit ToM, the reliance of many ToM tasks on complex language processing is another aspect that prevents a thorough investigation of differences in autistic and non-autistic people in ToM ability. Examples of such tasks are the Faux Pas task (Stone et al., 1998) and the Strange Stories task (Happé, 1994). For instance, in a study using the Strange Stories task, language ability was a better predictor of task performance than ToM in siblings of autistic children (Shaked et al., 2006). It is important to take language processing into account, because a large meta-analysis has recently shown that autistic people are impaired compared to neurotypical people in their structural language ability, e.g. verbal comprehension, verbal fluency and verbal learning (Velikonja et al., 2019). Studies also point to differences between the two groups in some aspects of pragmatic language ability (Angeleri et al., 2016; Rundblad & Annaz, 2010). Therefore, studies on autism and ToM need to be tightly controlled for language ability or use tasks that are non-verbal. Interestingly, a large multicenter study involving 205 autistic people using a nonverbal ToM task found no differences in brain activation between autistic and non-autistic participants (Moessnang et al., 2020). Several other studies that tested for ToM ability while controlling for language ability did not find differences between autistic and non-autistic people (Capps et al., 1998; Norbury, 2005; Tager-Flusberg & Sullivan, 1994). Because of these drawbacks in existing tasks, evidence of autistic people having decreased mentalizing ability is not conclusive (Gernsbacher & Yergeau, 2019). What is needed is a non-verbal, naturalistic, implicit ToM task that avoids the pitfalls summarized above and is therefore well-suited for comparing mentalizing between autistic and neurotypical populations. Recently, a ToM localizer task has been developed that meets these criteria. In the task, participants watch an animated movie (‘Partly Cloudy’ by Pixar Animation Studios) where characters interact with each other non-verbally (Jacoby et al., 2016). The task activates the core mentalizing network in neurotypical individuals and it has already been employed as a ToM localizer (Paunov et al., 2019). Yet, this task has only been used in neurotypical populations. Therefore, the objective of the proposed study is to compare ToM processing between autistic and neurotypical individuals with the localizer as conceived by Jacoby et al. (2016).