Normal IQ in Children
A normal Intelligence Quotient (IQ) in children is defined as a score between 85 and 115, which represents average intellectual functioning. 1
Standard IQ Classification
The standard IQ scoring system uses the following framework for interpretation:
- Average intelligence: IQ 85-115 1
- Borderline intellectual functioning: IQ 70-84 1
- Intellectual disability: IQ <70 1
- Above average intelligence: IQ >115 2
The mean IQ score is standardized at 100 with a standard deviation of 15 points, which means approximately 68% of children fall within one standard deviation (85-115) of the mean. 1
Important Caveats About IQ Testing
Age-Related Reliability
IQ measures are not considered reliable in children under 5 years of age, and the term "Global Developmental Delay" should be used instead for this age group when significant limitations exist in two or more developmental domains. 1
Limitations of Single IQ Scores
The profile of IQ subtests can be more helpful than the composite IQ score alone, as it reveals both cognitive strengths and weaknesses requiring support. 1, 3 The American Academy of Child and Adolescent Psychiatry emphasizes that IQ test scores are "approximations of conceptual functioning but may be insufficient to assess reasoning in real-life situations and mastery of practical skills." 1
Factors Affecting Test Performance
Performance on standardized IQ testing can be significantly influenced by multiple factors that may underestimate true cognitive abilities:
- Cultural and linguistic minorities may have underestimated scores due to test instrument limitations 1, 3
- Testing conditions including motivation, cooperation, interest, temperament, behavior, physical health, mental health, test setting, and tester attitude 1, 3
- Communication, sensory, and motor factors can affect reliability 1
- Severe intellectual disability or language impairment makes results less reliable 1, 3
Clinical Application
When to Reassess
Federal law requires re-evaluation at least every 3 years in school-aged children, and reassessment of IQ and adaptive functioning is particularly recommended at transition periods (e.g., primary to secondary school, secondary to post-secondary). 1, 4
Interpreting Discrepancies
Verbal IQ often exceeds Performance IQ by >10 points in certain conditions (such as 22q11.2 deletion syndrome), rendering full-scale IQ estimates less valid, which can significantly affect cognitive remediation planning. 1 Clinical training and judgment are required to interpret intellectual testing results and assess performance accurately. 1, 3
Beyond the IQ Score
Adaptive functioning must be assessed separately from IQ, as adaptive skills can be significantly lower than IQ scores even in children with average intelligence. 2 Standardized scales measuring adaptive behaviors do not capture all functional domains, thus adaptive functioning requires clinical assessment beyond standardized testing. 1