Can only intelligent children do mind reading: The relationship between intelligence and theory of mind in 8 to 11 years old
© Rajkumar et al; licensee BioMed Central Ltd. 2008
Received: 14 July 2008
Accepted: 11 November 2008
Published: 11 November 2008
The mind reading ability of children has evoked wide interest, but its relationship with general cognitive abilities remains obscure.
We studied the relationship between the mind reading ability and general intelligence. Children (N = 105) between 8 to 11 years from educational institutions were assessed for the mind reading ability using Picture Sequencing Task and Unexpected Contents Theory of Mind task. We used Strengths and Difficulties Questionnaire to rule out psychiatric morbidity. An independent investigator quantified intelligence and adaptive behavior with Binet- Kamat Test of intelligence and Vineland Adaptive Behavior Scale respectively. We employed bivariate and multivariate statistical tests.
We demonstrated that mind reading ability was not significantly related to general intelligence or its domains except for the social intelligence after controlling the confounders methodologically and statistically.
These findings argue that mind reading skill exists as an independent cognitive domain and has clinical, research as well as educational implications.
Can we explain children's ability to understand human minds by their sheer sense of intelligence? Will anyone of us bravely bet that the most intelligent student in a classroom is the best in that class to read minds? The cognitive ability to impute mental states to the self and others meaningfully, to predict and explain the intention of behaviors in terms of mental states is named as Mind reading or Theory of Mind (ToM) [1, 2]. ToM serves children to understand that others may hold as well as act upon beliefs different from theirs and appreciating such alternative perspectives is essential for successful social interaction.
Research on ToM had usually focused on its origin, development  and deficits . Theory of Mind is said to be active even in 15-month toddlers  and be deficient in a variety of psychiatric [6–8] as well as neurological disorders [9, 10]. However, ToM's independent existence as a specific cognitive domain is still controversial [11, 12].
To resolve this debate studying the relationship between ToM and general cognitive abilities is imperative. Previous studies have investigated the relationship between ToM and executive functions , language ability , and episodic memory  among children with compromised intelligence  or psychopathology [17, 18]. Among the various general cognitive abilities, Intelligence Quotient (IQ) is considered the main confounding factor in studying ToM . Currently, there is a significant paucity of research eliciting the relationship between the ToM and intelligence in typically developing children . Therefore, we opted to study the relationship between the ToM and intelligence along with its various domains in children over broad IQ ranges and with out any psychiatric morbidity.
Setting and sample
We recruited participants from 12 mainstream schools and four special schools for children with Intellectual Disability (ID) in the Vellore educational district, Tamilnadu, Southern India. The schools represent the higher (Private ICSC board schools), middle (Private matriculation board schools); lower socio-economic (Public state board schools) backgrounds and they represent the literate late childhood population in India.
Sample size estimation
We calculated sample size to identify correlation (rho = 0.3) between ToM and IQ. Keeping alpha error, beta error and a priori power at 5%, 20%, and 80% respectively, the sample size needed was 84, for a two-tailed evaluation. As we anticipated 20% drop out between the two points of assessment, we recruited at least 100 children in this study.
We included children of 8 to 11 years of age with their caregivers if they were willing to participate in the study. We excluded children with psychiatric morbidity, long-term physical illness, neurological deficits or disabilities, special sensory deficits, severe behavioral problems, long-term use of any medication, children who had already received prior training for ToM tasks and those unwilling to provide verbal assent or informed consent to participate in this study.
Theory of mind
The Binet-Kamat Scale of intelligence  is the Indian adaptation of the 1934 version of Stanford-Binet Scale of Intelligence. Some of tests, items and materials were amended to suit Indian conditions, such as Indian coins, typically Indian pictorial scenes, vocabulary and Indian concepts. This intelligence scale assessed the child's skills in nine domains: language, meaningful memory, non-meaningful memory, conceptual thinking, verbal reasoning, non-verbal reasoning, numerical reasoning, visuomotor coordination and social intelligence.
The Vineland Adaptive Behavior Scale (VABS) assesses the social competence of children with or without disabilities from birth to 19 years of age under four domains and 11 sub-domains .
The Strength Difficulty Questionnaire (SDQ) has 25 items that screen for psychological strengths and psychiatric disorders among children as well as categorize individuals with low needs; some needs and high needs . It identifies children with conduct disorder, hyperactivity, depressive and anxiety disorders needing various interventions .
Interview and assessment
APR, a qualified psychiatrist approached the children and their primary caregivers to enroll in this cross sectional study, according to the protocol approved by the hospital's Institutional Review Board. He obtained written informed consent from the primary care giver and verbal assent from the child before data collection. The interview and assessment protocol during the first day of evaluation required approximately two hours to complete. It consisted of three sections: (i) a face-to-face interview with open ended questions documenting the socio demographic data (ii) a structured assessment to screen for psychopathology using SDQ and for the ability to participate in ToM assessment using Unexpected Contents Theory of Mind task (iii) an in-depth ToM assessment with PST. During the second day of evaluation, SY, an experienced psychologist independently measured the intelligence and adaptive behavior using the BKT and the VABS respectively. Thus, we assessed 105 children of 8–11 years of age who satisfied the selection criteria and consented to participate in the study.
Preliminary checks of skewness and kurtosis and the one sample Kolmogorov Smirnoff tests verified that our data were suitable for parametric analysis. Firstly, we analyzed the socio-demographic data, cognitive profile, adaptive behaviors and ToM details for all the participants using descriptive statistics. Secondly, we grouped the participants into three IQ-based groups based on the conventional nomenclature : below average (IQ < 90); average (IQ 90–110); and above average (IQ > 110) intelligence. We compared the groups using Chi-square tests for categorical variables and one-way ANOVA for continuous variables. Thirdly, we analyzed the linear correlation between the ToM and various domains of general intelligence using Pearson's correlation coefficient tests. Finally, we also conducted the multiple linear regression analysis with ToM as the dependant variable to account for the effects of possible confounders. All tests used two-tailed analysis and a P value of less than 0.05 was considered significant. We analyzed our data using the statistical software package, SPSS 16.0.
Socio demographic profile of children and their families (N = 95)
Chronological age (in years):
Type of school:
Type of Family:
Age of father (in years)
Age of mother (in years)
Number of siblings:
One or more
Monthly family Income (Indian rupees/month)
F/H of psychiatric illness:
Psychological profile of children who participated in this study (N = 95)
Picture Sequencing Task
General Sequencing Ability
Theory of Mind ability
- 0.82 (1.29)
Binet Kamat Test
Mental Age (in years)
Language (in years)
Meaningful memory (in years)
Non meaningful memory (in years)
Conceptual thinking (in years)
Non verbal thinking (in years)
Verbal reasoning (in years)
Non verbal reasoning (in years)
Visuo motor (in years)
Social intelligence (in years)
Intelligence Quotient (IQ)
Vineland Adaptive Behavior Scale
Adaptive Behaviour composite age equivalent (in years)
The mechanical (rho = 0.74, P = 0.001), social script (rho = 0.65, P = 0.001), general sequencing ability (rho = 0.77, P = 0.001) and false belief scores (rho = 0.70, P = 0.001) of PST were significantly correlated with IQ. The selective accuracy Theory of Mind score was calculated by subtracting the general sequencing ability scores from the mean score of false belief sequences.
Correlationa matrix between Theory of Mind ability and intelligence domains of participants
The multiple linear regression analysis with ToM as the dependent variable also demonstrated the lack of a significant relationship between ToM and IQ when the above stated six socio-demographic confounders were controlled [β(SE) = -0.24 (0.01), t = -1.59, P = 0.12; Prep = 0.86]. The social intelligence domain [β(SE) = -0.55 (0.06), t = -3.75, P = 0.001; Prep = 0.99] and the visuomotor domain [β(SE) = -0.32 (0.09), t = -2.43, P = 0.02; Prep = 0.95] continued to exhibit significant relationship with ToM. When we further controlled for the effects of VABS adaptive behavior composite age equivalent, the lack of a significant relationship between ToM and IQ [β(SE) = 0.02 (0.01), t = 0.05, P = 0.96; Prep = 0.51] and significant relationship of the social intelligence domain [β(SE) = -0.91 (0.11), t = -3.75, P = 0.001; Prep = 0.99] and the visuomotor domain [β(SE) = -0.49 (0.11), t = -2.57, P = 0.012; Prep = 0.96] remained. Other domains of intelligence did not have significant relationship with ToM.
Our findings suggest that Theory of Mind is a distinct cognitive ability and not related to either general intelligence or its domains after controlling the confounders. ToM was related to social intelligence in our study and has also been documented before . This relationship between the ToM and social intelligence may not only reflect the association between the manifest social intelligence in the form of adaptive behavior but a true link between the social intelligence and ToM. This hypothesis needs further testing.
Language has been previously considered as having a robust linear relationship with the ToM even after accounting for the children's age and the verbal complexity of the tasks employed . However, the role of the culture and language as inherent components of the measures used to assess ToM has not been controlled in the past studies [31, 32]. In our study when we applied a non-verbal mode of ToM assessment and thus controlling the role of language and verbal skills inherent to the ToM measure, we demonstrated that ToM's correlation with language ability was not significant. The verbal and non-verbal memory functions were not related to ToM in our study and this finding has been noted previously . The significant relationship noted between the visuomotor ability and ToM has not been documented in the past and in our study this relationship could be attributed to the nature of the measure, because PST involves general sequencing ability based on the visuomotor skills.
The main limitations of the study are, the cross-sectional nature of the study and selecting children within particular age range that possibly reduce the stability of our findings in children whose cognitive domains are continuously developing. However, the strengths of our study are firstly, studying children from sub average to above average intelligence whereas most of the previous studies have used children with intellectual disability . Secondly, earlier studies did not control for the confounding effect of psychopathology on the relationship between intelligence and ToM [18, 20], and we have ruled out any psychopathology that could confound this relationship. Thirdly, data collection by two independent masked investigators and a fair follow up of the prerequisite sample size reduced the observer and attrition bias respectively. Then, the baseline differences between different intelligence groups were controlled statistically to remove their confounding effects on the relationship between IQ and ToM. Finally, the selection of participants from clinic and community population strengthens the generalizability of the findings.
Our study demonstrates a lack of significant linear relationship of ToM with the intelligence domains, language and memory as well as supports the argument that ToM exists as a specific independent cognitive domain. This study clarifies a puzzle in ToM research, facilitates interpretation of previous data and provides the impetus for pursuing neuro-cognitive studies to demarcate the biological systems underlying this cognitive domain. Our findings have potential implications in the fields of mental health, rehabilitation and education. Although it is standard research practice to interpret the study findings based on the null hypothesis and our study is robust in its results, replication of our findings will further establish this answer to the ToM-IQ riddle. Therefore, future studies should focus on the relationship between the intelligence and ToM with longitudinal designs and in cross-cultural settings.
List of abbreviations
Binet Kamat Scale of intelligence
Strength Difficulty Questionnaire
Mind reading or Theory of Mind
Vineland Adaptive Behavior Scale.
We thank Dr. Robyn Langdon, cognitive psychologist, Macquarie University, Sydney for providing the Picture Sequencing Task for the assessment of ToM; the staff of Department of Psychiatry, Christian Medical College, Vellore for their comments and suggestions; as well as the children and their parents who kindly agreed to participate in this research. This work was supported by Fluid Research Grant of Christian Medical College, Vellore, India.
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