Theory of mind (ToM) is considered to be one of the most important dimensions of social cognition,which refers to the ability to discriminate and judge mental states (i.e., wants, needs, beliefs, knowledge, emotions, etc.) of oneself and others.1−3 Research has found that in order to modify behavior in accordance with others, it is important to understand others' mental states.4 Hence, ToM ability, as a specific human skill, plays a vital role in interaction and everyday functioning.5−7 In other words, this ability facilitates social interaction of humans through understanding mental and emotional states of others.8 There are many studies that have found ToM deficits in psychological and neurological disorders such as mood disorders9 − 11, personality disorders7, anxiety disorders12, psychotic disorders13,14, Alzheimer disease15.
Theoretical frameworks of ToM categorize this ability into affective and cognitive aspects. According to Singer16, affective ToM refers to attribution of emotional states to others and cognitive ToM involves realization intentions of others. Recent theories have referred to affective and cognitive aspects as social-perceptual and social-cognitive components of ToM.17−19 The social-perceptual aspect, also known as the “affective aspect” of ToM, is the ability to decode and discriminate mental states of others based on available information, which can be recognized by the observer in the immediate environment.18 The social-cognitive aspect, known as the “cognitive aspect” of ToM, refers to ability to reason about the mental states through interpretation or prediction the behavior of others.17,18 The neurobiological substrates for the decoding phase or the affective aspect of ToM is the amygdala, the medial temporal structures, and the frontal lobe18,20, while the medial frontal area of brain identified as the most significant region corresponding with reasoning phase or cognitive aspect of ToM.21,22 In accordance with these differences in the affective and cognitive aspects of ToM, recent studies have simultaneously evaluated dysfunction in both aspects of ToM in particular psychological disorders (de la Osa et al., 2016; Zabihzadeh et al., 2017; Liu et al., 2017).4,7,23 For example, Zabihzadeh et al.7 takes this into consideration by considering the evaluation of ToM in patients with borderline personality disorder as indicated by their normal ability in affective aspects and deficits in cognitive aspects.
Affective disorders are a set of psychiatric conditions such as depression, bipolar, and anxiety disorders.24 Considering the high prevalence of affective disorders and dysfunction in the social interactions of patients with these disorders11,25,26,27, the evaluation of social cognition is a common subject throughout the literature28. An overview of literature has shown that among all affective disorders, the study of ToM in Major Depressive Disorder (MDD) has come to focus as compared to the other affective disorders.
Deficits in social functioning are some of the most well-known features of MDD.10 This dysfunction is also important in the onset and in maintaining depressive symptoms.26,29 Considering the importance of ToM in the social interactions, the evaluation of ToM ability in patients with MDD has been widely used in research.9−11,28−31 The results of these studies are consistent to a high extent and represent a dysfunction in ToM ability of depressed patients. Also, these findings have been repeated in other psychiatric conditions accompanied by the comorbid depression. According to Zabihzadeh et al.7, patients with borderline personality disorder with comorbid MDD had decreased ToM skills in comparison with other patients without comorbid MDD. This shortage of ToM ability in depressed patients correlates strongly with their impaired social abilities.8,10 Since interpersonal conflict is an important element in recurrence of depression29, ToM impairment seems to be a suitable predictor of depression reappearance along with the malfunction of these patients in their social interactions. Despite the fact that many studies have evaluated ToM in patients with MDD, only two studies by Wang et al.8 and Wolkenstein et al.9 have been conducted to simultaneously investigate the affective and cognitive aspects of ToM in these patients; however, their results are inconsistent. According to Wang et al.8, the MDD patients represented lower performance in both affective and cognitive dimensions of ToM in comparison with the healthy group. On the other hand, the results of Wolkenstein et al.9 indicate that MDD patients have lower performance only in cognitive ToM in comparison to the healthy group, while the performance of these patients in affective ToM is normal. Both studies used the Reading in the Mind of the Eyes Test (RMET)32 for measuring the affective ToM. Based on these inconsistencies, it seems that this subject requires further studies regarding the simultaneous measurement of affective and cognitive aspects of ToM in MDD patients.
Anxiety disorders are another type of affective disorders that is are highly prevalent. Despite the considerable studies on ToM in patients with depression, little research has been done on the ability of ToM in anxiety disorders, specifically in social anxiety disorder (SAD). SAD is known to be a common psychiatric disorder characterized by a persistent, excessive fear, and avoidance of social and performance situations24 and is a chronic and debilitating psychiatric condition, leading to social and interpersonal impairments27. Previous studies have proposed that high levels of social anxiety may partly be attributed to social cognition deficits, which are manifested as a tendency toward inaccurate and distorted appraisals of the beliefs and intentions of others during interpersonal interactions.33,34 Despite social and interpersonal dysfunction as a marked symptom in SAD, only three studies have assessed ToM ability in this disorder. According to Samson et al.35, the high scores in the social anxiety scale are associated with decreased ToM ability. This study had a predominant limitation, which is that it was conducted in individuals with social anxiety in the non-clinical range. Furthermore, in this study, ToM ability evaluated only with cartoons that involved the interpretation of others’ mental states. This task is most common for the measurement of cognitive ToM but not for the affective aspect. According to the results of Hezel & McNally36, SAD patients compared to the healthy group had a lower performance in ToM tasks, particularly in RMET, and within that the eyes depicted mental states of a negative valence.
The study of Washburn et al.27 is the only study that has considered ToM ability in the clinical case of SAD patients. The results of this study which had aimed to compare ToM in SAD and MDD patients with and without comorbid depression, demonstrated that the group of non-comorbid SAD had significantly lower performance in comparison with the healthy, and non-comorbid MDD groups. Further, both the comorbid and non-comorbid SAD groups made significantly more ‘excessive’ ToM reasoning errors than the non-comorbid MDD group, suggesting a pattern of over-mentalizing. Although in this study for evaluation of ToM ability both RMET32 and movie for the assessment of cognition (MASC)37 were used, but the main goal of research was not to differentiate the performance of patients in affective and cognitive aspect of ToM. For this reason, the results of this study had not discussed based on relationship between the performance of patients in ToM tasks with the affective and cognitive aspects.
Considering the limitations of the previous studies, the major purpose of our study is to a simultaneous comparison of the decoding and reasoning mental state or affective and cognitive aspects of ToM in MDD and SAD patients, and healthy controls (HC). According to the results of previous studies, we expect that the impairment of mind theory in MDD is more severe than SAD. Furthermore, we expect the HC group in both decoding and reasoning mental states to be better than MDD and SAD groups.