Children with attention deficit hyperactivity disorder who possess a distinct split between their verbal and nonverbal intelligence face greater challenges with self-control and focus. These mental gaps line up with lower blood flow in the front of the brain during tasks that require impulse management. The results were published in the journal NeuroImage.
Attention deficit hyperactivity disorder is one of the most common neurodevelopmental conditions in school-age children. Its primary traits include an inability to maintain focus, physical restlessness, or impulsive behavior. These symptoms often stem from weaknesses in executive function. Executive function acts as the brain’s management system, organizing thoughts, regulating emotions, and guiding planned behavior.
Psychologists frequently evaluate cognitive abilities using comprehensive assessments that divide intelligence into two main categories. Verbal intelligence involves language-based problem-solving, vocabulary, and accumulated factual knowledge. Performance intelligence deals with visual processing, spatial reasoning, and hands-on tasks like arranging blocks or recognizing patterns.
In typical development, a child’s scores in these verbal and performance categories are usually somewhat balanced. However, some children exhibit a wide split between the two scores, a condition described as an intelligence quotient discrepancy. Previous research has indicated that large splits between verbal and performance skills are unusually common among children who have attention issues.
Some theorists propose that verbal scores measure academic achievement and acquired information, while performance scores measure the raw ability to process new variables simultaneously. A gap between the two might reflect an underlying disruption in how different regions of the brain communicate. Xin Chen, a researcher at Fujian Children’s Hospital in China, and colleagues designed an experiment to see how this intelligence gap impacts day-to-day behavior.
The research team recruited 114 children diagnosed with attention deficit hyperactivity disorder. All participants were between the ages of six and twelve and had general intelligence test scores of 70 or higher. None of the children were currently taking medication for their attention symptoms.
Examiners administered a standard cognitive test to measure each child’s verbal and performance abilities. Based on the results, the investigators divided the children into two roughly matched groups. One group possessed a large gap between their verbal and performance scores. The other group had relatively balanced profiles without an intelligence gap.
To measure real-world skills, the research team asked the children’s parents to complete a standardized behavioral survey. The questionnaire asked caregivers to rate how often their child struggled with daily tasks. It covered specific categories like emotional control, physical organization, working memory, and task initiation.
The children also completed a computerized test to gauge their ability to process sights and sounds. The software required participants to click a mouse when they saw or heard the number one. They were instructed to hold back completely when they encountered the number two. This allowed the researchers to measure both raw reaction times and the ability to suppress an incorrect response.
To understand the biological mechanisms behind these behaviors, the scientists selected a random subset of 46 children. This smaller group underwent brain imaging while performing a second computerized assessment. The researchers utilized a noninvasive imaging technique called functional near-infrared spectroscopy.
Functional near-infrared spectroscopy uses a specialized cap fitted with small light sensors. These sensors project harmless beams of near-infrared light through the scalp and skull. By measuring how the light scatters and bounces back, 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 out which brain areas are working the hardest.
While wearing the sensor cap, the subset of children played a game meant to trigger their impulse control. The screen displayed images of different animals in quick succession. The children were told to press a button as fast as possible when they saw a cat or a dog.
At random intervals, the game switched its rules. When an image of a chicken appeared, the children had to press the button. When an image of a duck appeared, they had to entirely stop themselves from reacting.
The overall results revealed a distinct pattern among the children who possessed an intelligence gap. On the parent surveys, this group scored worse on overall executive function compared to the children with balanced intelligence. Caregivers reported that children with an intelligence gap struggled the most with starting new tasks and shifting smoothly between different activities.
Similar outcomes appeared during the computerized visual and auditory tests. The group with an intelligence gap recorded slower overall reaction times. They had particular difficulty with the visual portions of the test, committing more errors when trying to hold back a mouse click.
When researchers looked back at the original intelligence tests, they noticed the biggest difference between the two groups came down to arithmetic scores. Arithmetic requires a child to hold numbers in their working memory and manipulate them mentally. The scientists suggest that this specific weakness heavily influences how severe a child’s attention symptoms might appear.
The brain imaging data provided a biological reflection of these behavioral struggles. During the animal game, the children with an intelligence gap showed reduced blood flow to the right medial prefrontal cortex. This brain area is heavily involved in regulating emotions, maintaining motivation, and making decisions.
The researchers found a direct relationship between the severity of a child’s attention deficits and the lack of blood flow in that specific frontal region. Children whose parents reported the highest levels of daily distractibility showed the lowest levels of oxygenated blood in the medial prefrontal cortex. Conversely, the results were not statistically significant when the researchers looked at the left prefrontal cortex or the temporal lobes.
Through statistical modeling, the team also identified a behavioral trait known as monitoring as a primary indicator for hyperactivity and scattered attention. Monitoring is the mental ability to supervise one’s own work to ensure a goal is met. Children who lack this supervisory skill are highly prone to careless errors in school and social settings.
The study authors listed several caveats to their findings. The project relied on older, revised editions of standard intelligence and behavioral assessments. Relying on these older formats might make it difficult to compare the current data against research conducted with newly updated testing standards.
Additionally, the participant pool was limited exclusively to Chinese children. Behaviors and test outcomes can be influenced by cultural or educational environments, meaning the results might not automatically apply to other populations. The study design also grouped all types of attention deficit hyperactivity disorder together, rather than separating children who are mostly hyperactive from those who just struggle to focus.
The investigators also did not include a control group of typically developing children. Having a baseline comparison would help isolate whether the blood flow patterns are unique to the intelligence gap or a broader feature of attention deficits. Future projects will need to incorporate larger sample sizes and different types of cognitive tasks.
Brain imaging technology also has inherent limitations. The light sensors can pick up noise from superficial blood flow in the scalp, which can sometimes blur the deeper brain signals. The authors suggest that subsequent experiments should use advanced equipment channels to filter out surface-level interference.
The study, “Effect of Intelligence Quotient Discrepancy 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.