**1. Introduction**

unaffected siblings of probands with autism spectrum disorder. JAMA Psychiatry

[81] Hudry K, Chandler S, Bedford R, Pasco G, Gliga T, Elsabbagh M, Johnson MH, Char‐ man T. Early language profiles in infants at high-risk for autism spectrum disorders.

Journal of Autism and Developmental Disorders 2014;44(1) 154-167.

2013;70(1) 42-48.

112 Autism Spectrum Disorder - Recent Advances

In a seminal study, conducted almost 30 years ago, Baron-Cohen, Leslie and Frith [1] provided first empirical support for the idea that individuals with autism spectrum disorders (ASD) have a Theory of Mind (ToM) deficit, i.e. they are impaired in the fundamental human ability to attribute mental states like beliefs, desires or intentions to themselves and others and therefore fail to explain and predict behavior in a commonsense way in everyday interactions (see [2]). Baron-Cohen et al. [1] used a task in which story character Sally does not witness story character Anne transferring a ball from a basket to a box and thus falsely believes it is still in its original location. Twelve-year-old participants with ASD systematically based their prediction of Sally's search behavior on their own knowledge about the situation and failed the test, answering she will look for the ball in its new location. Crucially, typically developed children and children with Down's Syndrome who were matched for mental age, passed the task. It was concluded that participants with ASD were specifically impaired in adopting Sally's perspective, that is, in attributing a false belief to her. Since then, a wealth of studies confirmed this ToM deficit in children and adults with ASD (e.g., [3]).

Despite its major contributions to explaining core symptoms of autism (social deficits, deficits in pragmatic language, imaginative play, and empathy), the ToM hypothesis has also been criticized for failing to provide a specific account for the social and cognitive impairments, especially in high functioning individuals with ASD [4]. First, verbal skills strongly predict performance on verbal ToM tasks [5]. In some studies, when verbal ability was entered as a covariate, ToM did not predict the degree of social impairments in children and adults with ASD [6]. Second, ToM deficits are not specific to ASD, but have also been observed in clinical groups with for example schizophrenia [7] and deafness [8]. Third, ToM skills assessed in standard experimental tasks may not be informative of real-world social competencies and

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deficits, since experimental situations do not pose the kinds of stressful demands on individ‐ uals with ASD that real-life social situations do. This may be one reason for the failure of ToMbased interventions to enhance real-world social competencies [9].

In the last ten years, new methods, relying on spontaneous and implicit ToM processing have been productively used to further investigate the social and cognitive impairments in ASD. These methods were first used in infant research; infants and young children under the age of about 4 years, like patients with ASD, fail explicit ToM tasks, but nevertheless show a spon‐ taneous sensitivity to others' mental states in looking-time, eye-tracking, and interactive tasks [10]. An implicit ToM appears to developmentally precede an explicit one (two-systems accounts; [11]).

Explicit ToM reasoning describes the ability to deliberately consider others' mental states and provide reasons in order to explain their behavior ("Sally will look for the ball in the basket because she falsely believes it is still in there"; see [12]). This form of ToM reasoning acts consciously, can be flexibly employed in various situations, and is cognitively demanding. Explicit ToM tasks, like the Sally-Anne task, test this ability by assessing verbal responses to the direct question for the protagonist's mental state and belief-based behavior.

Implicit ToM reasoning refers to the spontaneous sensitivity to others' mental states without the need to deliberately reflect on them. It is supposed to work fast, unconsciously, but rigidly. Implicit ToM tasks, clever nonverbal versions of the Sally-Anne task, assess the participant's gaze in anticipation of the protagonist's belief-based behavior as an indicator of implicit ToM reasoning (e.g., [13]). In the first section of the present chapter, we review the research on implicit ToM processing in ASD.

Not all spontaneous ToM processing is implicit. The spontaneous use of mental state terms in everyday conversations is one of the first signs for an explicit understanding of mental states in child development, with talk about volitional states and emotions, beginning in the second year of life and preceding cognitive language by over one year [14]. While some usages of mental state terms serve conversational functions without genuine reference to mental states [14], there is evidence for specific relations between cognition terms and perspective taking abilities [15] and for predictive relations between preverbal communicative abilities and mental state language [16] in child development. Since the study of mental state language in ASD poses fewer restrictive task demands than experimental ToM tasks, it may add to our understanding of mental state representation in ASD in important ways. The second part of the present chapter focuses on this line of research.
