Children with Attention Deficit Hyperactivity Disorder, who have a clear divide between verbal and nonverbal intelligence, face significant challenges in self-control and concentration. These mental gaps coincide with reduced blood flow to the front of the brain during tasks that require impulse control. The results were published in the magazine NeuroImage.
Attention-deficit hyperactivity disorder is one of the most common neurodevelopmental disorders in school-age children. Its main characteristics include an inability to maintain concentration, physical restlessness, or impulsive behavior. These symptoms often result from weaknesses in executive function. Executive function functions as the brain’s management system, organizing thoughts, regulating emotions, and guiding planned actions.
Psychologists often assess cognitive abilities using comprehensive assessments that divide intelligence into two major categories. Linguistic intelligence includes language-based problem solving, vocabulary, and accumulated factual knowledge. Performance intelligence deals with practical tasks such as visual processing, spatial reasoning, and block placement and pattern recognition.
During typical development, children’s scores in these language and performance categories are usually somewhat balanced. However, some children have a large gap between the two scores, a condition called intelligence quotient discrepancy. Previous research has shown that children with attention problems disproportionately exhibit large disparities between their language and executive abilities.
Some theorists have proposed that verbal scores measure academic performance and information acquired, while performance scores measure raw ability to simultaneously process new variables. The gap between the two may reflect a fundamental disruption in how different regions of the brain communicate. Xin Chen, a researcher at China’s Fujian Children’s Hospital, and his colleagues designed an experiment to see how this intelligence gap affects everyday behavior.
The research team recruited 114 children diagnosed with attention deficit hyperactivity disorder. All participants were between 6 and 12 years old and had a general intelligence test score of 70 or higher. None of the children were currently taking medication for attention symptoms.
Examiners administered standardized cognitive tests to measure each child’s language and executive abilities. Based on the results, the researchers divided the children into two roughly matched groups. One group had a large gap between their language and performance scores. The other group had a relatively balanced profile with no intelligence gaps.
To measure real-world skills, the researchers asked the children’s parents to complete a standardized behavioral survey. The questionnaire asked caregivers to rate the extent to which their child struggled with daily tasks. We covered specific categories such as emotional control, body organization, working memory, and task initiation.
The children also completed computer tests to measure their ability to process sights and sounds. The software required participants to click the mouse when they saw or heard the number 1. They were instructed to completely refrain from encountering Number Two. This allowed the researchers to measure both raw reaction time and the ability to inhibit incorrect responses.
To understand the biological mechanisms behind these behaviors, scientists randomly selected a subset of 46 children. This small group underwent brain imaging during a second computerized assessment. The researchers used a non-invasive imaging technique called functional near-infrared spectroscopy.
Functional near-infrared spectroscopy uses a special cap fitted with a small optical sensor. These sensors shine harmless near-infrared light through the scalp and skull. By measuring how light is scattered and reflected, the system can detect changes in the concentration of oxygenated blood. Active brain tissue requires more oxygen, so tracking blood flow allows researchers to map which brain regions are working the hardest.
While wearing the sensor cap, some children played a game that triggered impulse control. Images of various animals were displayed one after another on the screen. Children were asked to press a button as soon as possible when they saw a cat or dog.
At random intervals, the rules of the game changed. When an image of a chicken appeared, the children had to press a button. They had to stop reacting completely when the image of a duck appeared.
The overall results revealed clear patterns among children who differed in intelligence. In parent surveys, this group had worse overall executive function scores compared to children with balanced intelligence. Parents reported that children with intelligence differences had the most difficulty starting new tasks and transitioning smoothly between different activities.
Computerized visual and auditory tests showed similar results. The group with differences in intelligence recorded slower overall reaction times. They had particular difficulty with the visual part of the test, making even more errors when trying to suppress mouse clicks.
When researchers looked back at the original intelligence tests, they found that the biggest difference between the two groups was in math scores. Mathematics requires children to hold numbers in working memory and manipulate them mentally. Scientists suggest that this particular weakness has a significant impact on how severe a child’s attention symptoms appear.
Brain imaging data provided a biological reflection of these behavioral struggles. During animal games, children with differences in intelligence showed decreased blood flow to the medial right prefrontal cortex. This brain region is deeply involved in regulating emotions, maintaining motivation, and decision-making.
Researchers found a direct relationship between the severity of a child’s attention deficit and the lack of blood flow in that particular frontal region. Children whose parents reported the highest daily distractibility had the lowest levels of oxygen-rich blood in the medial prefrontal cortex. Conversely, when researchers looked at the left prefrontal cortex or temporal lobe, the results were not statistically significant.
Through statistical modeling, the researchers also identified a behavioral trait known as monitoring as a key indicator of hyperactivity and divided attention. Monitoring is the mental ability to oversee one’s work to ensure that goals are achieved. Children who lack this supervisory skill are much more likely to make careless mistakes in school and social settings.
The study authors offer several caveats to their results. This project relied on older revisions of the Standard Intelligence and Behavioral Assessment. Reliance on these outdated formats can make it difficult to compare current data with studies conducted with newly updated test standards.
Additionally, participants were limited to Chinese children only. Behavior and test results can be influenced by cultural or educational environments, meaning that results do not automatically apply to other populations. The study design grouped all types of attention-deficit hyperactivity disorder together, rather than distinguishing between children who were primarily hyperactive and those who struggled to concentrate.
The researchers also did not include a control group of typically developing children. Baseline comparisons can help identify whether blood flow patterns are specific to intelligence disparities or a broader feature of attention deficits. Future projects should incorporate larger sample sizes and different types of cognitive tasks.
Brain imaging techniques also have inherent limitations. Light sensors can pick up noise from blood flow on the surface of the scalp, which can blur signals from the deep brain. The authors suggest that subsequent experiments should use advanced instrument channels to remove surface-level interference.
The study, “The influence of intelligence quotient mismatch on attention and executive function in children with attention-deficit hyperactivity disorder: an fNIRS study,” was authored by Xin Chen, Liang-liang Chen, Jing-rong Wang, Ying-ying Cai, and Xiao-dan Yu.
