Social Competence in Children with Borderline Intellectual Functioning: Delayed Development of Theory of Mind Across All Complexity Levels

Borderline intellectual functioning (BIF) is characterized by heterogeneous cognitive difficulties, with an intelligence quotient (IQ) between 70 and 85 points, and a failure to meet the developmental and sociocultural standards for personal independence and social responsibility required in daily life. The fact that this population still remain a marginal clinical category, with no ad hoc diagnostic and therapeutic approaches, has stimulated the present research. Our goal was to study children with BIF investigating the development of Theory of Mind (ToM) as a pillar of social competence. Children with BIF (N = 28, 16 male/12 female, and mean age 9.46 ± 1.26 years) and children with typical development (TD; N = 31, 17 male/14 female; mean age 8.94 years ± 0.99) underwent a neurocognitive assessment and a ToM assessment. Children with BIF showed a significant lower performance across all the levels of ToM development investigated compared to the control group, and a correlation between executive functions and the advanced levels of ToM reasoning. These results constitute a first step in the direction of defining the clinical profile of children with BIF concerning ToM development, opening the way to future interventions in order to support the developmental evolution of this population in an adaptive direction.

Introduction

Borderline intellectual functioning (BIF) is a controversial nosographic entity and a marginal clinical category that remains to be clearly defined (Cornoldi et al., 2014) and for which targeted diagnostics and therapeutic approaches do not exist.

Borderline intellectual functioning has been recently defined as a boundary status between disease and typical development, not stemming from a single neurodevelopmental syndrome and with heterogeneous functioning profiles (Salvador-Carulla et al., 2013). It is characterized by a wide range of cognitive difficulties, with an intelligence quotient (IQ) between 70 and 85 points, and a failure to meet the developmental and sociocultural standards for personal independence and social responsibility that affects daily activity (American Psychiatric Association, 2000, 2013; Tangney et al., 2004; Salvador-Carulla et al., 2013; Kok et al., 2016).

The lack of international consensus on diagnostic criteria makes it difficult to determine the current BIF prevalence. Some studies have reported a frequency ranging from 2% (Voigt et al., 2006) to 7–18% in the overall population (Ninivaggi, 2001; Salvador-Carulla et al., 2013), and around 7% among the school age population (Karande et al., 2008).

Typically, children with BIF show a heterogeneous neuropsychological profile (Salvador-Carulla et al., 2013; Peltopuro et al., 2014) including difficulties in executive functions, i.e., working memory, problem solving, and attention (Alloway, 2010; Schuchardt et al., 2010). The concern with this condition lies in its impact on the quality of everyday life of the affected subjects (Ninivaggi, 2001; Karande et al., 2008; Fernell and Ek, 2010; Salvador-Carulla et al., 2013). Indeed, this condition is closely associated with failure of social expectations, such as school dropouts, social isolation, inadequate affective relationships, and with the risk of developing mental illnesses in adolescence or adulthood, e.g., depression, suicidal ideation, self-harm, emotional distress, anxiety and antisocial disorders and, finally, future socio-economic disadvantage (Hassiotis et al., 1999, 2008; Douma et al., 2007; Emerson and Hatton, 2007; Ferrari, 2007; Karande et al., 2008; Emerson et al., 2010, 2011; Fernell and Ek, 2010; Peltopuro et al., 2014). A large part of these impairments, namely behavioral and affective disorders (Cook and Oliver, 2011; van Nieuwenhuijzen and Vriens, 2012), are an expression of a low social adaptive functioning and can be traced back to a lack of adequate complex socio-cognitive skills (Schalock et al., 2011).

A pivotal role in the social competences growth is played by Theory of Mind (ToM) or mentalization, i.e., the ability to attribute mental states (intentions, desires, emotions, and beliefs) to ourselves and others and to predict, on the basis of such inferences, our own and others’ behavior (Wimmer and Perner, 1983). An adequate level of ToM development and functioning has a cascade effect on other acquisitions, because ToM is involved in the increase of self-awareness, in the encoding of others’ behavior, in the self-regulation of emotions, in mastering novel problems and situation, in efficacious communication processes and, finally, in building satisfying relationships (Hughes and Leekam, 2004; Caputi et al., 2012; Ghrear et al., 2016). ToM evolves early in human development and seems to be strictly embedded with many cognitive and affective processes, such as frontal functions (Amodio and Frith, 2006; Grossmann, 2013; Devine and Hughes, 2014) emphatic concern (Ibanez et al., 2013) and affective syntonization (Xavier et al., 2013; Baimel et al., 2015), and attachment (Fonagy and Target, 1997). During development, ToM acquisition proceeds toward two levels of representation: abilities to construct ‘simple’ representations of another person’s mental states (as beliefs or thoughts, i.e., ‘What does John think?’) and more complex attributions (‘What does Paul think that Mary thinks?’). Learned in late childhood, the latter are considered to require more cognitive resources (for a review, see Miller, 2009), in particular competences executive functions (Leslie et al., 2005).

Given the relevance of ToM in social adaptive adjustment, several studies have investigated this competence in intellectual disability (ID) demonstrating a strong correlation between concrete reasoning and ToM impairments (Adrien et al., 1995; Baron-Cohen et al., 1999; Corcoran, 2001; Capozzi et al., 2009; Brojčin et al., 2014). Specifically, Schalock et al. (2011) highlighted a delay in the acquisition of the first and second order false belief reasoning—i.e., the ability to engage in complex levels of recursive thinking—in a sample of children with moderate ID. Moreover, Jervis and Baker (2004) discovered that children with non specific ID had better performance on ToM tasks compared to adults with equal intellectual capacity. This would be due to the increment in social isolation that occurs over the years and that is frequently associated with ID.

However, cognitive competences are necessary but not sufficient for ToM development. Despite the importance of these abilities in ToM development, a normal IQ can be associated with very poor performance in social skills and ToM tasks. For example, some subjects with high functioning autism (Baron-Cohen et al., 2001) remain strongly impaired in everyday social interactions despite high IQ profiles. This finding suggests that the link between IQ and ToM development deserves further consideration, especially in the population of children with BIF, in which the latter is associated with impairment in social skills.

On the basis of this evidence, we suppose that an inadequate ToM functioning is likely to be connected with a social impairment in the case of BIF. Given the lack of data about ToM in children with BIF and their risk to develop social disadvantages with age, we have explored this construct in this population in comparison with children with typical development (TD). Moreover, we explored the correlation between performance in an advanced ToM task and IQ. To this purpose, we used the Strange Stories task that strongly involves both cognitive functioning and social competences. Finally, given the importance of executive functions, in particular working memory, in ToM (Devine and Hughes, 2014) and in BIF, we investigated, in children with BIF, their connection with the performance in the Strange Stories task. Twenty-eight children with BIF and a group of 31 age-matched children with TD were studied through multiple ToM tasks and IQ measures.

Materials and Methods

Participants

Two groups of children, one with BIF and one with TD comparable for chronological-age and gender were included. All participants attended mainstream primary schools, near Don Gnocchi Foundation, and showed middle socio-economic status.

Twenty-eight children with BIF (16 male/12 female, mean age of 9.46 ± 1.26 years), with IQ ranging from 70 to 85, were enrolled in the study. A clinical interview revealed learning and social difficulties in all children with BIF. They were recruited from the Adolescence and Pediatric Neuropsychiatry Unit of our institution.

As control group 31 healthy students with TD (17 male/14 female; mean age of 8.94 years ± 0.99) and no history of neurological, psychiatric or systemic disease nor learning disability were enrolled through selection from the mainstream schools.

All children included in the study had never taken medications and underwent a clinical evaluation in order to exclude genetic syndromes, i.e., Down syndrome or X Fragile syndrome, and/or major neuropsychiatric problems, such as autism spectrum disorder or attention deficit hyperactivity disorder, other neurological conditions (epilepsy and traumatic brain injury), malformations, or systemic diseases, such as diabetes or immune disorders, and infectious disease involving the central nervous system.

The present study was approved by the scientific and ethics committees of (Don Gnocchi Foundation and Catholic University of the Sacred Heart). Parents gave written informed consent for participation in the study.

Neuropsychological Assessment

All children were screened for general intelligence with the Wechsler Intelligence Scale for Children-III (Wechsler, 1991; Orsini and Picone, 2006).

Within their routine clinical evaluation, children with BIF underwent a neuropsychological assessment of executive functions which included: Semantic and Phonological Fluency (from the Neuropsychological Assessment Battery for children: BVN 5-11; Bisiacchi, 2005); the Working Memory Index (WMI from WISC-IV; Wechsler, 2003; Orsini et al., 2012) that included the subsequent subtest digit span and letter-number sequencing; modified Bells test accuracy and rapidity (Biancardi and Stoppa, 1997) a barrage task that evaluates immediate and sustained selective attention; Tower of London (TOL; Sannio Fancello et al., 2006) a task to measure planning ability and inhibitory control.

All these tests are standardized and their psychometrics properties are illustrated in their respective manuals and references.

ToM Assessment

All participants were tested with a paper-pencil ToM battery in order to assess their level of mentalizing development. For a more sensitive measurement of ToM ability, the battery consisted of a first order false belief task (Deceptive Box Task; Perner et al., 1987); two second order false belief tasks, Look-prediction task (Astington et al., 2002; Antonietti and Giorgetti, 2006; Castelli et al., 2014) and Ice-cream story (Perner and Wimmer, 1985; Marchetti et al., 2014) and advanced ToM tasks, i.e., a selection of four Strange Stories and their control task, the Physical Stories (Happé, 1994; Happé et al., 1998; Mazzola, 2002). Each task provides for one or more control questions to test the understanding of the logical order and the explicit elements in the story without inferring mental states. These tools are designed as research assessments and are widely used to investigate this construct in a life-span perspective (Fonagy and Allison, 2012). Meta-analyses confirm the validity of the ToM battery used in this study both in typical (Wellman et al., 2001; Henry et al., 2013) and atypical population (Stewart et al., 2016).

The first order false belief task consists of a real experience of a false belief. A closed candies box, whose content has been secretly substituted with an unexpected object, is shown to the participants who are asked to say what it contains. After the discovery of their own false belief, the box is closed again and the investigator asks them to predict what another person would say when shown the closed box. The participants are asked three control questions and two test questions regarding the false belief, the first concerning that of another person, and the second for one’s own false belief. 1 point is assigned in the case of a correct answer, whereas 0 in the case it was incorrect.

The second order false belief tasks are more complex tasks, suitable to test a higher level of mentalistic reasoning. Through the Look-prediction task it is possible to evaluate the acquisition of the second order false belief reasoning because the situation that is presented to the participants requires high order, recursive mentalistic reasoning. The story is told and the participants have to predict where the co-protagonist, on the basis of his/her false belief, would think that the other person will look for the object. The main elements of the story are illustrated with pictures that remain available during the whole interview in order to reduce as much as possible the memory load. In the same way, the Ice cream story, the classical second order false belief task, explores the abilities to manage the mental contents employed in the story. For the Look-prediction five questions are asked, two of which are used as controls, one as an explanation, and the remaining two are the actual test questions. The Ice-cream story, included three control questions, one explanation question and one test question. In both tasks 1 point is assigned in the case of correct answer, whereas 0 in the case it was incorrect.

The Strange Stories task measures a higher level of ToM because of their complexity and structure. Each story describes a daily situation and refers to a specific mental content i.e. double bluff, white lie, misunderstanding and persuasion. Participants have to decode not only the mental content but also the dynamic of the story in a single and coherent view (see Castelli et al., 2011 for a complete description of this ToM battery). For each story there is one control question (except for the double bluff story, which has two) and one test question. All the tasks described were chosen as they have been shown to be sufficiently reliable and valid measures of ToM competences for children in the age range included in this study (Happé, 1994; Wellman et al., 2001). 0 point is assigned in the case of incorrect answer, 1 in the case the answer was incomplete or partially correct, finally 2 for a full and complete answer. In addition, it is possible to code if subjects use mental state term (MS, e.g., thinks, knows, wants, etc.) or if an inappropriate mental state is attributed (MSx). A recent study (Devine and Hughes, 2016) showed the reliability and the validity in childhood of Strange Stories.

The whole battery was administered individually; answers were audio-recorded and then coded once the session was closed.

Procedure

Children with BIF were tested at Don Gnocchi foundation whereas children with TD at school. All participants were individually tested in a quiet room in two sessions: the first for the WISC-III and the second for the ToM battery. This was administered with increasing complexity sequence.

Data Analysis

Statistical analyses were conducted with MedCalc software (v14.8.1). Demographic and intellectual functioning differences between groups were tested using the t-test or χ² test as appropriated.

Theory of Mind data were screened based on a conservative inclusion criteria: for each participant, only the stories in which the control questions were answered correctly were included in the analyses. The scoring of each story included only the test and the explanation questions. Control questions were only used as inclusion criteria and thus were excluded from the total score.

The two groups were compared by ANCOVA analyses with age as covariate of no interest, using a General linear model (GLM) to explore differences in the following variables: performance at first order false belief task (Deceptive box, score 0 to 2); at second order false belief task (Ice cream story and Look-prediction, score ranging from 0 to 6); Strange Stories (score ranging from 0 to 8) and Physical Stories (score ranging from 0 to 8). Furthermore, to test relationship between performance in advanced ToM task (Strange Stories) and IQ Pearson’s correlation analyses were performed: Strange Stories and WISC-III score; Strange Stories and executive functions tests (semantic and phonological fluency, WMI) within the two groups (TD and BIF). Moreover, to explore the link between advanced ToM task (Strange Stories) and executive functions we performed an additional correlation analysis.

Results

Group Differences in Age, Gender, and IQ

Children with BIF were not significantly different from children with TD on the matching variables of age and gender (Table 1). Performance on the WISC-III was significantly different between the two groups as expected as the inclusion criteria were also based on IQ (Table 1).

TABLE 1

TABLE 1. Means and standard deviations (SD) of the sample’s demographics and performance at WISC III.

Results of the neuropsychological assessment of executive functions of children with BIF are shown in Figure 1: performances were in the borderline range in all tests.

FIGURE 1

FIGURE 1. Results of the neuropsychological assessment of executive functions of children with borderline intellectual functioning (BIF). The colored box indicates performance in the borderline range, i.e., between -1 and -2 Z-scores.

Group Differences in ToM Performance

Regarding the performance at the ToM tasks, the two groups of children performed similarly with respect to the control questions. This means that the two groups were equal in the capacity to understand the concrete contents of the story and to remember the main information. Concerning the false belief tasks, the statistical analysis between children with TD and children with BIF highlighted a significant difference for the first order total score index of the deceptive box task (ANCOVA p < 0.05; Table 2) and for the second-order Look-prediction task, and no difference for the second-order Ice-cream task. For the Ice-cream task, fewer participants passed the filter of the control questions (only 21 children with TD and 16 with BIF), thus showing that this story was more difficult to understand in its contents, besides the false beliefs inferences, for both groups (Table 2).

TABLE 2

TABLE 2. Comparison of the ToM abilities between the two groups of children.

Regarding the advanced ToM tasks, we found significantly lower performance of children with BIF compared to children with TD in the Strange Stories (p < 0.05), with no differences in the performance on the Physical Stories tasks (Table 2).

Correlation between Intellectual Functioning and ToM Competences

To investigate the role of intellectual functioning in ToM abilities, we performed a correlation analysis between Strange Stories and WISC III scores in children with TD.

Results showed significant correlations only between the Strange Stories task and two WISC-III subtests: Picture completion (p < 0.05) and Picture Arrangement scores (p < 0.05) (Figure 2; Table 3).

FIGURE 2

FIGURE 2. Results of the correlation between Strange Stories and WISC-III subtests in children with typical development (TD) and BIF.

TABLE 3

TABLE 3. Pearson’s correlations between performance at the Strange Stories task and Wisc-III scores.

To determine the impact of borderline intellectual functioning in ToM abilities we performed the same correlations as above in children with BIF. A significant correlation was found only between the Strange Stories task score and Similarities (abstract reasoning; p < 0.05), Coding (p < 0.05), and Digit Span scores (p < 0.05; Figure 2). Table 3 summarizes the correlation analysis between the Strange Stories task and IQ scores.

Correlation between Executive Functions and ToM Performace in Children with BIF

To test the relation between ToM abilities and executive functions we performed a correlation between Strange Stories and the fluency tests and Working Memory Index. Results showed a significant correlation between Strange Stories performance and semantic fluency and Working Memory Index, and a tendency toward the significance with phonological fluency (Table 4).

TABLE 4

TABLE 4. Correlation between the Strange Stories task and executive functions in children with BIF.

Discussion

The principal aim of this study was to determine if children with BIF, characterized by a low IQ and difficulties to meet developmental and socio-cultural standards, show a pattern of ToM abilities which deviates from the one observed in typically developing children.

The first result that we found was the absence of significant differences between the two groups in the control questions of the ToM tasks. This demonstrates that all participants were able to overcome the task when mental contents were not included in the reasoning, presenting a comparable instruction comprehension and understanding of the cause–effect relationship of the facts narrated in the stories. Indeed, in these exercises, participants were required to understand the logical order of the events and to answer questions only on the basis of the elements that are explicit in the story, i.e., without inferring mental states.

However, significant differences between the two groups were found when children were required to consider the characters’ mental states. This was true across all ToM tasks, from the simplest one, the first order false belief, to the more advanced ones, the Strange Stories. In fact, children with BIF performed lower than children with TD at Deceptive Box, a task that can be considered as the baseline of ToM reasoning, as it evaluates first-order false belief, and it is usually overcome around 4 years of age (Wimmer and Perner, 1983). In this task, both short-term memory and the ability to decentralize one’s own point of view are stimulated; the comprehension of the task is made easier by the participants’ direct experience of the real situation. Nevertheless, our data show that children with BIF did not perform at the expected developmental standards. In addition, children with BIF performed lower than children with TD in the second order false belief tasks, which evaluate a more difficult level of recursive thinking. This aspect of ToM is usually successfully managed around 7–9 years of age (Perner and Wimmer, 1985). The story is more complex than the first order false belief one, with an increasing number of agents engaged in embedded mental states. Children with BIF were not able to distinguish what each character actually knew from their own omniscient knowledge. In all these stories, characters have only incomplete or partial information about the events, as happens in daily life. It is from this lack of information that the false belief reasoning takes place. The participants should be able to handle such absence by incorporating the other’s beliefs. In order to do that, they must identify and keep in mind all the relevant information to have various prospects at the same time and manage the situation. Finally, differences between the two groups were found also in the advanced ToM tasks, where multiple cognitive and affective abilities are strictly involved (Happé, 1994). Events are put into a social context, where the understanding of the protagonists’ behavior requires an affective syntonization, the assumption of the character’s intentions, the anticipation, and prediction of others possible behaviors. These results seem to indicate a delay in ToM abilities development. This hypothesis deserves future investigation with a control group matched for mental age.

Because ToM, in particular advanced ToM ability, is closely embedded with cognitive competences, we explored the impact of global intelligence on this complex process. We looked into the specific intellectual functioning of each group to determine how this interacted with advanced ToM tasks such as the Strange Stories. Results showed a positive correlation with the Picture Completion and the Picture Arrangement subtests in children with TD. These two tasks require rapid visual-perceptive analysis and processing. To be effectively solved, they necessitate the use of global cognitive strategies for a rapid and complete analysis of all the elements rather than an analytical approach that focuses on perceptual details (Vakil and Lifshitz-Zehavi, 2012). Indeed, the latter is more time demanding. Moreover, in our opinion, the Picture Arrangement subtest of the WISC-III requires a large degree of ToM to be accomplished: some stories require irony and sense of humor to understand intentions of the others or consequences of someone’s actions or chain of events. On the other hand, the Picture Completion requires the ability to anticipate the object’s mental image to identify its main elements and therefore the missing one, a skill highly involved in ToM tasks.

Differently, children with BIF showed a pattern of positive correlations with Similarities, Coding and Digit Span. These subtests assess short-term and working memory (Digit span and Coding), inhibitory control and novel material learning ability (Coding) and verbal fluid reasoning (Similarities), all abilities that engage functions connected with the frontal lobe (executive functions and FI). Moreover, we found that performance of children with BIF at executive function tests were in the borderline range and correlated (verbal fluency and working memory index) significantly with the Strange Stories task scores. Many studies demonstrated that children with BIF have difficulties in executive functions (Henry and MacLean, 2002; van der Meer and van der Meere, 2004; Van der Molen et al., 2007, 2009, 2014; Bonifacci and Snowling, 2008; Alloway, 2010; Hartman et al., 2010; Henry and Winfield, 2010). Our explanation is that our results may be due to the poor executive functions of children with BIF leading to an overload of information with the increasing of the complexity of the tasks. Poor executive functions could affect the capacity to keep online the main information of the story (for example the characters or their actions) while they select and handle those necessary to master the situation. The hypothesis of an overload of data could, also, underpin the preference of children with BIF for analytic analysis, as highlighted in another study (Vakil and Lifshitz-Zehavi, 2012).

The connection between ToM abilities and executive function that we found is also supported by several studies (see for a review, Devine and Hughes, 2014). An important aspect of executive functions relates to the ability to constantly update personal knowledge with new information, to learn by experience and master real life situation adaptively and to be socially competent. Recent studies have demonstrated that psychosocial adaptation is also connected to fluid intelligence (FI; Huepe et al., 2011), defined as the ability to reason and solve new problems independently from the acquired knowledge (Cattell, 1963; Cattell, 1967; Duncan, 2005; for a review see Nisbett et al., 2012). Executive functions and FI are strictly embedded; in fact FI is also important to modulate the ToM as demonstrated in experiments with the Eyes Test, which is an advanced ToM task (Ibanez and Manes, 2012; Ibanez et al., 2013; Baker et al., 2014). FI and executive functions are, indeed, engaged not only in cold information processing, such as logical and abstract reasoning, but also in hot processing, such as social cognition. This confirms the cross-influences existing between the cognitive and the social-affective processes (Liverta Sempio and Marchetti, 1995).

In our study, the positive correlation between the Strange Stories task and the Similarities that we found in children with BIF can be connected not only with FI but also with a deficit in meta-representational competences, as demonstrated in other studies involving children with mild to borderline intellectual disabilities (Karmiloff-Smith et al., 1995; Melogno and Becciu, 1999; Ivancich Biaggini, 2004; Capozzi et al., 2009). Indeed, ToM requires meta-representational abilities, such as lower-order representations (i.e., representations of reality) and higher-order representations (i.e., the ability to form thoughts about attributed thoughts).We suppose that when there is an overload of information to be processed, children with BIF face difficulty with both types of meta-representations that are necessary for both tasks: Strange Stories and Similarities.

Moreover, our results showed that children with BIF perform poorly on all false belief tasks, even the easiest ones. These children seem to be still dealing with the belief-desire psychology stage, which is an early (around 3–4 years of age) evolution step. At this level children understand that actions are driven by desires, thought, intention and true belief but they are not able to comprehend that behavior can also be justified by misinterpretation, i.e., false belief.

Conclusion

The results of our study show that children with BIF have a deficit in ToM that is strictly connected with their executive functions and meta-representation competences. These results can be important to develop treatment strategies able to support these children in their social skills during childhood and to prevent the social disadvantages that they might face in adulthood.

Many evidences from the literature prove that ToM is not an all-or-nothing process, but rather it is a set of skills that people continue to develop during the whole life (Fonagy and Allison, 2012). Nevertheless, we are aware that “ToM is sometimes necessary, but never sufficient”, to quote Astington (Astington, 2003) and that future studies are needed to explore the impact of ToM in everyday social life of children with BIF.

The results suggest that an early intervention is essential to support the mentalization development (Fabio et al., 2009, 2013) as already demonstrated in other disabilities (Fonagy and Allison, 2012). In the specific case of children with BIF, the timing of the intervention is crucial. Many studies have shown that the “window of opportunity” is particularly open and fruitful during childhood (Alexander and Entwisle, 1988; Alexander et al., 1995), as brain plasticity (see a Dennis et al., 2013 for a review) and the opportunity to positively influence the developmental course are increased (Pianta and Walsh, 1996). Furthermore, recent studies have demonstrated a cerebral cortical developmental delay in children with BIF (Baglio et al., 2014). According to these evidences, it is essential to better understand the functioning difficulties of children with BIF. This will allow for the development of targeted strategies to minimize the gap with their peers as soon as possible and to redirect these children toward a typical developmental pattern.

Author Contributions

All authors have reviewed critically the work, provided important intellectual content and approved the final form.

GB, VB, and FB designed the research, analyzed data, interpreted the results and drafted the manuscript; GB also performed neuropsychological and ToM evaluation; MZ recruited patients and analyzed the clinical data. FS, IC, DM, AV, and AM have dealt with supplying ToM tasks material, analyzing ToM data and drafted the manuscript.

Funding

This research was funded by the Ricerca Corrente of the Italian Ministry of Health.

Conflict of Interest Statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Acknowledgment

The authors wish to thank all the children and their families for participating in the study and Dr. Niels Bergsland for his careful revision of the English language.

References

Adrien, J. L., Martineau, J., Barthélémy, C., Bruneau, N., Garreau, B., and Sauvage, D. (1995). Disorders of regulation of cognitive activity in autistic children. J. Autism. Dev. Disord. 25, 249–263. doi: 10.1007/BF02179287

CrossRef Full Text | Google Scholar

Alexander, J. M., Carr, M., and Schwanenflugel, P. J. (1995). Development of metacognition in gifted children: directions for future research. Dev. Rev. 15, 1–37. doi: 10.1006/drev.1995.1001

CrossRef Full Text | Google Scholar

Alexander, K. L., and Entwisle, D. R. (1988). Achievement in the first 2 years of school: patterns and processes. Monogr. Soc. Res. Child Dev. 53, 1–157. doi: 10.2307/1166081

CrossRef Full Text | Google Scholar

Alloway, T. P. (2010). Working memory and executive function profiles of individuals with borderline intellectual functioning. J. Intellect. Disabil. Res. 54, 448–456. doi: 10.1111/j.1365-2788.2010.01281.x

PubMed Abstract | CrossRef Full Text | Google Scholar

American Psychiatric Association (2000). Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR), 4th Edn. Washington, DC: American Psychiatric Association.

Google Scholar

American Psychiatric Association (2013). Diagnostic and Statistical Manual of Mental Disorders (DSM-5). Washington, DC: American Psychiatric Pub.

Google Scholar

Amodio, D. M., and Frith, C. D. (2006). Meeting of minds: the medial frontal cortex and social cognition. Nat. Rev. Neurosci. 7, 268–277. doi: 10.1038/nrn1884

PubMed Abstract | CrossRef Full Text | Google Scholar

Antonietti, A., and Giorgetti, M. (2006). Teachers’ beliefs about learning from multimedia. Comput. Hum. Behav. 22, 267–282. doi: 10.1016/j.chb.2004.06.002

CrossRef Full Text | Google Scholar

Astington, J. W. (2003). “Sometimes necessary, never sufficient: false-belief understanding and social competence,” in Individual Differences in Theory of Mind: Implications for Typical and a Typical Development, eds B. Repacholi and V. Slaughter (New York, NY: Psychology Press), 13–38.

Google Scholar

Astington, J. W., Pelletier, J., and Homer, B. (2002). Theory of mind and epistemological development: the relation between children’s second-order false-belief understanding and their ability to reason about evidence. New Ideas Psychol. 20, 131–144. doi: 10.1016/S0732-118X(02)00005-3

PubMed Abstract | CrossRef Full Text | Google Scholar

Baglio, F., Cabinio, M., Ricci, C., Baglio, G., Lipari, S., Griffanti, L., et al. (2014). Abnormal development of sensory-motor, visual temporal and parahippocampal cortex in children with learning disabilities and borderline intellectual functioning. Front. Hum. Neurosci. 8:806. doi: 10.3389/fnhum.2014.00806

PubMed Abstract | CrossRef Full Text | Google Scholar

Baimel, A., Severson, R. L., Baron, A. S., and Birch, S. A. (2015). Enhancing “theory of mind” through behavioral synchrony. Front. Psychol. 6:870. doi: 10.3389/fpsyg.2015.00870

PubMed Abstract | CrossRef Full Text | Google Scholar

Baker, C. A., Peterson, E., Pulos, S., and Kirkland, R. A. (2014). Eyes and IQ: a meta-analysis of the relationship between intelligence and “Reading the mind in the eyes”. Intelligence 44, 78–92. doi: 10.1016/j.intell.2014.03.001

CrossRef Full Text | Google Scholar

Baron-Cohen, S., O’Riordan, M., Stone, V., Jones, R., and Plaisted, K. (1999). Recognition of faux pas by normally developing children and children with asperger syndrome or high-functioning autism. J. Autism. Dev. Disord. 29, 407–418. doi: 10.1023/A:1023035012436

CrossRef Full Text | Google Scholar

Baron-Cohen, S., Wheelwright, S., Hill, J., Raste, Y., and Plumb, I. (2001). The “Reading the mind in the eyes” test revised version: a study with normal adults, and adults with asperger syndrome or high-functioning autism. J. Child Psychol. Psychiatry 42, 241–251. doi: 10.1111/1469-7610.00715

CrossRef Full Text | Google Scholar

Biancardi, A., and Stoppa, E. (1997). Il test delle campanelle modificato (TCM) una proposta per lo studio dell’attenzione in età evolutiva. Psichiatr. Dell Infanz. Dell Adolescenza 64, 73–84.

Bisiacchi, P. S. (2005). BVN 5-11 Batteria di Valutazione Neuropsicologica per l’età Evolutiva. Gardolo: Erickson.

Google Scholar

Bonifacci, P., and Snowling, M. J. (2008). Speed of processing and reading disability: a cross-linguistic investigation of dyslexia and borderline intellectual functioning. Cognition 107, 999–1017. doi: 10.1016/j.cognition.2007.12.006

PubMed Abstract | CrossRef Full Text | Google Scholar

Brojčin, B., Glumbić, N., and Ɖorđević, M. (2014). Theory of mind acquisition in children and adolescents with mild intellectual disability. Specijalna Edu. Rehabil. 13, 11–34. doi: 10.5937/specedreh13-5428

CrossRef Full Text | Google Scholar

Capozzi, F., Ivancich Biaggini, V., and Penge, R. (2009). Disabilità intellettiva e rappresentazione mentale:Per un modello funzionale. Psichiatria Dell’Infanzia Dell’Adolesc. 76, 212–224.

Google Scholar

Caputi, M., Lecce, S., Pagnin, A., and Banerjee, R. (2012). Longitudinal effects of theory of mind on later peer relations: the role of prosocial behavior. Dev. Psychol. 48, 257. doi: 10.1037/a0025402

PubMed Abstract | CrossRef Full Text | Google Scholar

Castelli, I., Massaro, D., Bicchieri, C., Chavez, A., and Marchetti, A. (2014). Fairness norms and theory of mind in an ultimatum game: judgments, offers, and decisions in school-aged children. PLoS ONE 9:e105024. doi: 10.1371/journal.pone.0105024

PubMed Abstract | CrossRef Full Text | Google Scholar

Castelli, I., Pini, A., Alberoni, M., Liverta-Sempio, O., Baglio, F., Massaro, D., et al. (2011). Mapping levels of theory of mind in alzheimer’s disease: a preliminary study. Aging Ment. Health 15, 157–168. doi: 10.1080/13607863.2010.513038

PubMed Abstract | CrossRef Full Text | Google Scholar

Cattell, R. B. (1963). Theory of fluid and crystallized intelligence: a critical experiment. J. Educ. Psychol. 54, 1–22. doi: 10.1037/h0046743

CrossRef Full Text | Google Scholar

Cattell, R. B. (1967). The theory of fluid and crystallized general intelligence checked at the 5-6 year-old level. Br. J. Educ. Psychol. 37, 209–224. doi: 10.1111/j.2044-8279.1967.tb01930.x

PubMed Abstract | CrossRef Full Text | Google Scholar

Cook, F., and Oliver, C. (2011). A review of defining and measuring sociability in children with intellectual disabilities. Res. Dev. Disabil. 32, 11–24. doi: 10.1016/j.ridd.2010.09.021

PubMed Abstract | CrossRef Full Text | Google Scholar

Corcoran, R. (2001). “Theory of mind and schizophrenia,” in Social Cognition and Schizophrenia, eds P. W. Corrigan and D. L. Penn (Washington, DC: American Psychological Association).

Google Scholar

Cornoldi, C., Giofre, D., Orsini, A., and Pezzuti, L. (2014). Differences in the intellectual profile of children with intellectual vs. learning disability. Res. Dev. Disabil. 35, 2224–2230. doi: 10.1016/j.ridd.2014.05.013

PubMed Abstract | CrossRef Full Text | Google Scholar

Dennis, M., Spiegler, B. J., Juranek, J. J., Bigler, E. D., Snead, O. C., and Fletcher, J. M. (2013). Age, plasticity, and homeostasis in childhood brain disorders. Neurosci. Biobehav. Rev. 37(10 Pt 2), 2760–2773. doi: 10.1016/j.neubiorev.2013.09.010

PubMed Abstract | CrossRef Full Text | Google Scholar

Devine, R. T., and Hughes, C. (2014). Relations between false belief understanding and executive function in early childhood: a meta-analysis. Child Dev. 85, 1777–1794. doi: 10.1111/cdev.12237

PubMed Abstract | CrossRef Full Text | Google Scholar

Devine, R. T., and Hughes, C. (2016). Measuring theory of mind across middle childhood: reliability and validity of the silent films and strange stories tasks. J. Exp. child psychol. 149, 23–40. doi: 10.1016/j.jecp.2015.07.011

PubMed Abstract | CrossRef Full Text | Google Scholar

Douma, J. C., Dekker, M. C., de Ruiter, K. P., Tick, N. T., and Koot, H. M. (2007). Antisocial and delinquent behaviors in youths with mild or borderline disabilities. Am. J. Ment. Retard. 112, 207–220. doi: 10.1352/0895-8017(2007)112[207:AADBIY]2.0.CO;2

CrossRef Full Text | Google Scholar

Duncan, J. (2005). Frontal lobe function and general intelligence: why it matters. Cortex 41, 215–217. doi: 10.1016/S0010-9452(08)70896-7

PubMed Abstract | CrossRef Full Text | Google Scholar

Emerson, E., Einfeld, S., and Stancliffe, R. J. (2011). Predictors of the persistence of conduct difficulties in children with cognitive delay. J. Child Psychol. Psychiatry 52, 1184–1194. doi: 10.1111/j.1469-7610.2011.02413.x

PubMed Abstract | CrossRef Full Text | Google Scholar

Emerson, E., and Hatton, C. (2007). Reducing the risks. Ment. Health Today 23–25.

Google Scholar

Emerson, E., Shahtahmasebi, S., Lancaster, G., and Berridge, D. (2010). Poverty transitions among families supporting a child with intellectual disability. J. Intellect. Dev. Disabil. 35, 224–234. doi: 10.3109/13668250.2010.518562

PubMed Abstract | CrossRef Full Text | Google Scholar

Fabio, R. A., Antonietti, A., Castelli, I., and Marchetti, A. (2009). Attention and communication in rett syndrome. Res. Autism Spectr. Disord. 3, 329–335. doi: 10.1016/j.rasd.2008.07.005

CrossRef Full Text | Google Scholar

Fabio, R. A., Castelli, I., Marchetti, A., and Antonietti, A. (2013). Training communication abilities in rett syndrome through reading and writing. Front. Psychol. 4:911. doi: 10.3389/fpsyg.2013.00911

PubMed Abstract | CrossRef Full Text | Google Scholar

Fernell, E., and Ek, U. (2010). Borderline intellectual functioning in children and adolescents - insufficiently recognized difficulties. Acta Paediatr. 99, 748–753. doi: 10.1111/j.1651-2227.2010.01707.x

PubMed Abstract | CrossRef Full Text | Google Scholar

Ferrari, M. (2007). Borderline intellectual functioning in adult clinical populations. Arch. Clin. Neuropsychol. 22, 893.

Google Scholar

Fonagy, P., and Allison, E. (2012). “Cos’é la mentalizzazione? Il concetto e le sue basi nella ricerca sullo sviluppo,” in Minding the Child: Mentalization-Based Intervention with Children, Young People and their Families (trad. it: La Mentalizzazione Nel Ciclo di Vita. Interventi con Bambini, Genitori e Insegnanti), eds N. Migdley and I. Vrouva (Milano: Raffaello Cortina).

Fonagy, P., and Target, M. (1997). Attachment and reflective function: their role in self-organization. Dev. Psychopathol. 9, 679–700. doi: 10.1017/S0954579497001399

PubMed Abstract | CrossRef Full Text | Google Scholar

Ghrear, S. E., Birch, S. A., and Bernstein, D. M. (2016). Outcome knowledge and false belief. Front. Psychol. 7:118. doi: 10.3389/fpsyg.2016.00118

PubMed Abstract | CrossRef Full Text | Google Scholar

Grossmann, T. (2013). The role of medial prefrontal cortex in early social cognition. Front. Hum. Neurosci. 7:340. doi: 10.3389/fnhum.2013.00340

PubMed Abstract | CrossRef Full Text | Google Scholar

Happé, F. G. (1994). An advanced test of theory of mind: understanding of story characters’ thoughts and feelings by able autistic, mentally handicapped, and normal children and adults. J. Autism Dev. Disord. 24, 129–154. doi: 10.1007/BF02172093

CrossRef Full Text | Google Scholar

Happé, F. G., Winner, E., and Brownell, H. (1998). The getting of wisdom: theory of mind in old age. Dev. Psychol. 34, 358. doi: 10.1037/0012-1649.34.2.358

PubMed Abstract | CrossRef Full Text | Google Scholar

Hartman, E., Houwen, S., Scherder, E., and Visscher, C. (2010). On the relationship between motor performance and executive functioning in children with intellectual disabilities. J. Intellect. Disabil. Res. 54, 468–477. doi: 10.1111/j.1365-2788.2010.01284.x

PubMed Abstract | CrossRef Full Text | Google Scholar

Hassiotis, A., Strydom, A., Hall, I., Ali, A., Lawrence-Smith, G., Meltzer, H., et al. (2008). Psychiatric morbidity and social functioning among adults with borderline intelligence living in private households. J. Intellect. Disabil. Res. 52(Pt 2), 95–106. doi: 10.1111/j.1365-2788.2007.01001.x

PubMed Abstract | CrossRef Full Text | Google Scholar

Hassiotis, A., Ukoumunne, O., Tyrer, P., Piachaud, J., Gilvarry, C., Harvey, K., et al. (1999). Prevalence and characteristics of patients with severe mental illness and borderline intellectual functioning. Report from the UK700 randomised controlled trial of case management. Br. J. Psychiatry 175, 135–140. doi: 10.1192/bjp.175.2.135

PubMed Abstract | CrossRef Full Text | Google Scholar

Henry, J. D., Phillips, L. H., Ruffman, T., and Bailey, P. E. (2013). A meta-analytic review of age differences in theory of mind. Psychol. Aging 28, 826. doi: 10.1037/a0030677

PubMed Abstract | CrossRef Full Text | Google Scholar

Henry, L., and Winfield, J. (2010). Working memory and educational achievement in children with intellectual disabilities. J. Intellect. Disabil. Res. 54, 354–365. doi: 10.1111/j.1365-2788.2010.01264.x

PubMed Abstract | CrossRef Full Text | Google Scholar

Henry, L. A., and MacLean, M. (2002). Working memory performance in children with and without intellectual disabilities. Am. J. Ment. Retard. 107, 421–432. doi: 10.1352/0895-8017(2002)107<0421:WMPICW>2.0.CO;2

CrossRef Full Text | Google Scholar

Huepe, D., Roca, M., Salas, N., Canales-Johnson, A., Rivera-Rei,ÁA., Zamorano, L., et al. (2011). Fluid intelligence and psychosocial outcome: from logical problem solving to social adaptation. PLoS ONE 6:e24858. doi: 10.1371/journal.pone.0024858

PubMed Abstract | CrossRef Full Text | Google Scholar

Hughes, C., and Leekam, S. (2004). What are the links between theory of mind and social relations? review, reflections and new directions for studies of typical and atypical development. Soc. Dev. 13, 590–619. doi: 10.1111/j.1467-9507.2004.00285.x

CrossRef Full Text | Google Scholar

Ibanez, A., Huepe, D., Gempp, R., Gutiérrez, V., Rivera-Rei, A., and Toledo, M. I. (2013). Empathy, sex and fluid intelligence as predictors of theory of mind. Pers. Individ. Differ. 54, 616–621. doi: 10.1016/j.paid.2012.11.022

CrossRef Full Text | Google Scholar

Ibanez, A., and Manes, F. (2012). Contextual social cognition and the behavioral variant of frontotemporal dementia. Neurology 78, 1354–1362. doi: 10.1212/WNL.0b013e3182518375

PubMed Abstract | CrossRef Full Text | Google Scholar

Ivancich Biaggini, V. (2004). Funzionamento cognitivo borderline in età evolutiva: un rischio sottovalutato? Psicol. Clin. Dello Sviluppo 8, 25–49.

Google Scholar

Jervis, N., and Baker, M. (2004). Clinical and research implications of an investigation into theory of mind (ToM) task performance in children and adults with non-specific intellectual disabilities. J Appl. Res. Intellect. Disabil. 17, 49–57. doi: 10.1111/j.1468-3148.2004.00172.x

CrossRef Full Text | Google Scholar

Karande, S., Kanchan, S., and Kulkarni, M. (2008). Clinical and psychoeducational profile of children with borderline intellectual functioning. Indian J. Pediatr. 75, 795–800. doi: 10.1007/s12098-008-0101-y

PubMed Abstract | CrossRef Full Text | Google Scholar

Karmiloff-Smith, A., Klima, E., Bellugi, U., Grant, J., and Baron-Cohen, S. (1995). Is there a social module? language, face processing, and theory of mind in individuals with williams syndrome. J. Cogn. Neurosci. 7, 196–208. doi: 10.1162/jocn.1995.7.2.196

PubMed Abstract | CrossRef Full Text | Google Scholar

Kok, L., van der Waa, A., Klip, H., and Staal, W. (2016). The effectiveness of psychosocial interventions for children with a psychiatric disorder and mild intellectual disability to borderline intellectual functioning: a systematic literature review and meta-analysis. Clin. Child Psychol. Psychiatry 21, 156–171. doi: 10.1177/1359104514567579

PubMed Abstract | CrossRef Full Text | Google Scholar

Leslie, A. M., German, T. P., and Polizzi, P. (2005). Belief-desire reasoning as a process of selection. Cognit. Psychol. 50, 45–85. doi: 10.1016/j.cogpsych.2004.06.002

PubMed Abstract | CrossRef Full Text | Google Scholar

Marchetti, A., Castelli, I., Sanvito, L., and Massaro, D. (2014). Is a bird in the hand worth two in the future? intertemporal choice, attachment and theory of mind in school-aged children. Front.Psychol 5:483. doi: 10.3389/fpsyg.2014.00483

PubMed Abstract | CrossRef Full Text | Google Scholar

Mazzola, V. (2002). Strane Storie: Versione Italiana a Cura di Mazzola e Camaioni. Roma: Universita La Sapienza.

Google Scholar

Melogno, S., and Becciu, M. M. (1999). Comprensione metaforica e consapevolezza metalinguistica nei bambini borderline cognitivi. Psichiatr. Dell Infanz. Dell Adolesc. 64, 707–716.

Google Scholar

Miller, S. A. (2009). Children’s understanding of second-order mental states. Psychol. Bull. 135, 749. doi: 10.1037/a0016854

PubMed Abstract | CrossRef Full Text | Google Scholar

Ninivaggi, F. J. (2001). Borderline intellectual functioning in children and adolescents: reexamining an underrecognized yet prevalent clinical comorbidity. Conn. Med. 65, 7–11.

PubMed Abstract | Google Scholar

Nisbett, R. E., Aronson, J., Blair, C., Dickens, W., Flynn, J., Halpern, D. F., et al. (2012). Intelligence: new findings and theoretical developments. Am. Psychol. 67, 130–159. doi: 10.1037/a0026699

PubMed Abstract | CrossRef Full Text | Google Scholar

Orsini, A., Pezzuti, L., and Picone, L. (2012). WISC-IV: Contributo Alla Taratura ITALIANA. [WISC-IV Italian Edition]. Florence: Giunti O. S.

Google Scholar

Orsini, A., and Picone, L. (2006). WISC-III. Contributo Alla Taratura Italiana. [WISC-III Italian Edition]. Florence: Giunti O. S.

Google Scholar

Peltopuro, M., Ahonen, T., Kaartinen, J., Seppala, H., and Narhi, V. (2014). Borderline intellectual functioning: a systematic literature review. Intellect. Dev. Disabil. 52, 419–443. doi: 10.1352/1934-9556-52.6.419

PubMed Abstract | CrossRef Full Text | Google Scholar

Perner, J., Leekam, S. R., and Wimmer, H. (1987). Three–year–olds’ difficulty with false belief: the case for a conceptual deficit. Br. J. Dev. Psychol. 5, 125–137. doi: 10.1111/j.2044-835X.1987.tb01048.x

CrossRef Full Text | Google Scholar

Perner, J., and Wimmer, H. (1985). ‘John thinks that mary thinks that’: attribution of second-order false-belief by 5 to 10-years-old-children. J. Exp. Child Psychol. 5, 125–137.

Google Scholar

Pianta, R., and Walsh, D. (1996). High-Risk Children in Schools: Constructing Sustaining Relationships. New York: Routledge.

Google Scholar

Salvador-Carulla, L., Garcia-Gutierrez, J. C., Ruiz Gutierrez-Colosia, M., Artigas-Pallares, J., Garcia Ibanez, J., Gonzalez Perez, J., et al. (2013). Borderline intellectual functioning: consensus and good practice guidelines. Rev. Psiquiatr. Salud Ment. 6, 109–120. doi: 10.1016/j.rpsm.2012.12.001

PubMed Abstract | CrossRef Full Text | Google Scholar

Sannio Fancello, G., Vio, C., and Cianchetti, C. (2006). TOL Torre di Londra. Test di Valutazione Delle Funzioni Esecutive (Pianificazione e Problem Solving). Trento: Erickson.

Google Scholar

Schalock, R. L., Verdugo, M. A., and Gomez, L. E. (2011). Evidence-based practices in the field of intellectual and developmental disabilities: an international consensus approach. Eval. Program Plann. 34, 273–282. doi: 10.1016/j.evalprogplan.2010.10.004

PubMed Abstract | CrossRef Full Text | Google Scholar

Schuchardt, K., Gebhardt, M., and Maehler, C. (2010). Working memory functions in children with different degrees of intellectual disability. J. Intellect. Disabil. Res. 54, 346–353.

PubMed Abstract | Google Scholar

Liverta Sempio, O., and Marchetti, A. (1995). Il Pensiero DELL’ALTRO. Contesto, Conoscenza e Teoria Della Mente. Milan: Raffaello Cortina.

Google Scholar

Stewart, E., Catroppa, C., and Lah, S. (2016). Theory of mind in patients with epilepsy: a systematic review and meta-analysis. Neuropsychol. Rev. 26, 3–24. doi: 10.1007/s11065-015-9313-x

PubMed Abstract | CrossRef Full Text | Google Scholar

Tangney, J. P., Baumeister, R. F., and Boone, A. L. (2004). High self-control predicts good adjustment, less pathology, better grades, and interpersonal success. J. Pers. 72, 271–324. doi: 10.1111/j.0022-3506.2004.00263.x

PubMed Abstract | CrossRef Full Text | Google Scholar

Vakil, E., and Lifshitz-Zehavi, H. (2012). Solving the raven progressive matrices by adults with intellectual disability with/without down syndrome: different cognitive patterns as indicated by eye-movements. Res. Dev. Disabil. 33, 645–654. doi: 10.1016/j.ridd.2011.11.009

PubMed Abstract | CrossRef Full Text | Google Scholar

van der Meer, D. J., and van der Meere, J. (2004). Response inhibition in children with conduct disorder and borderline intellectual functioning. Child Neuropsychol. 10, 189–194. doi: 10.1080/09297040490911005

CrossRef Full Text | Google Scholar

Van der Molen, M. J., Henry, L. A., and Van Luit, J. E. (2014). Working memory development in children with mild to borderline intellectual disabilities. J. Intellect. Disabil. Res. 58, 637–650. doi: 10.1111/jir.12061

PubMed Abstract | CrossRef Full Text | Google Scholar

Van der Molen, M. J., Van Luit, J. E., Jongmans, M. J., and Van der Molen, M. W. (2007). Verbal working memory in children with mild intellectual disabilities. J. Intellect. Disabil. Res. 51, 162–169. doi: 10.1111/j.1365-2788.2006.00863.x

PubMed Abstract | CrossRef Full Text | Google Scholar

Van der Molen, M. J., Van Luit, J. E., Jongmans, M. J., and Van der Molen, M. W. (2009). Memory profiles in children with mild intellectual disabilities: strengths and weaknesses. Res. Dev. Disabil. 30, 1237–1247. doi: 10.1016/j.ridd.2009.04.005

PubMed Abstract | CrossRef Full Text | Google Scholar

van Nieuwenhuijzen, M., and Vriens, A. (2012). (Social) cognitive skills and social information processing in children with mild to borderline intellectual disabilities. Res. Dev. Disabil. 33, 426–434. doi: 10.1016/j.ridd.2011.09.025

PubMed Abstract | CrossRef Full Text | Google Scholar

Voigt, R. G., Barbaresi, W. J., Colligan, R. C., Weaver, A. L., and Katusic, S. K. (2006). Developmental dissociation, deviance, and delay: occurrence of attention-deficit-hyperactivity disorder in individuals with and without borderline-to-mild intellectual disability. Dev. Med. Child Neurol. 48, 831–835. doi: 10.1111/j.1469-8749.2006.tb01231.x

PubMed Abstract | CrossRef Full Text | Google Scholar

Wechsler, D. (1991). Wechsler Intelligence Scale for Children, 3rd Edn. New York, NY: Psychological Corporation.

Google Scholar

Wechsler, D. (2003). WISC-IV Technical and Interpretive Manual. San Antonio, TX: Psychological Corporation.

Google Scholar

Wellman, H. M., Cross, D., and Watson, J. (2001). Meta analysis of theory of mind development: the truth about false belief. Child Dev. 72, 655–684. doi: 10.1111/1467-8624.00304

CrossRef Full Text | Google Scholar

Wimmer, H., and Perner, J. (1983). Beliefs about beliefs: representation and constraining function of wrong beliefs in young children’s understanding of deception. Cognition 13, 103–128. doi: 10.1016/0010-0277(83)90004-5

CrossRef Full Text | Google Scholar

Xavier, J., Tilmont, E., and Bonnot, O. (2013). Children’s synchrony and rhythmicity in imitation of peers: toward a developmental model of empathy. J. Physiol. Paris 107, 291–297. doi: 10.1016/j.jphysparis.2013.03.012

PubMed Abstract | CrossRef Full Text | Google Scholar