Development of Reasoning Style in ADHD: A Cross-Sectional Gaze Movement Study with Children and Adolescents

The human mind is a master of strategy. When faced with a complex puzzle, we do not simply guess; we scan, we compare, and we build a mental model of how the pieces fit together. This ability to reason through patterns is a cornerstone of human intelligence, often measured by tests that ask people to find the missing piece in a grid of shapes. For decades, scientists have known that the way people solve these puzzles changes as they grow older. Young children tend to jump between the puzzle and the possible answers, testing options one by one. As they mature, they learn to study the puzzle first, figure out the rules, and then select the answer. This shift from guessing to logical construction is a key part of cognitive development. However, for children with attention-deficit/hyperactivity disorder, or ADHD, the path to this mature way of thinking is less clear. While it is known that these children often face challenges with focus and executive function, it remains uncertain whether their internal strategy for solving problems is fundamentally different from their peers, or if it simply reflects differences in their general reasoning ability.

To explore this, researchers at several universities in Germany and Greece set out to watch the eyes of children and teenagers as they solved puzzles. They recruited 160 participants, aged nine to seventeen, half of whom had a confirmed diagnosis of ADHD and half of whom were developing typically. The group sat before a computer screen and looked at a series of nine puzzles known as Raven's Matrices. Each puzzle presented a three-by-three grid of geometric patterns with one square missing, and the participant had to choose the correct missing piece from a set of options below. While they worked, a high-speed camera tracked their eye movements with extreme precision, recording every time their gaze landed on the puzzle or the answer choices. The researchers were not just interested in whether the children got the right answer, but in the journey their eyes took to get there. They wanted to see if the children with ADHD looked at the world differently while they were thinking.

The study revealed that the way a person approaches a puzzle is deeply tied to their age and their intelligence. As children grew older, their eyes spent more time studying the puzzle itself before ever glancing at the answer choices. This behavior, known as constructive matching, is the hallmark of an efficient problem-solver: they build a solution in their mind before testing it. The researchers found that this shift happened steadily throughout childhood and adolescence. Furthermore, children with higher scores on intelligence tests were more likely to use this efficient strategy, regardless of their age. They spent more time analyzing the patterns and less time hopping back and forth between the puzzle and the answers. This suggests that the ability to hold a complex visual pattern in mind and reason through it is a skill that grows alongside general intelligence.

When the researchers compared the children with ADHD to their peers, a clear difference appeared at first glance. The children with ADHD spent less time looking at the puzzle and more time looking at the answer choices. They also switched their gaze back and forth more frequently, a behavior that suggests a less systematic approach to the task. However, the story became more nuanced when the researchers accounted for intelligence. The children with ADHD in this study had, on average, lower intelligence scores than the control group. When the researchers statistically adjusted for this difference in ability, the gap in eye movement patterns largely disappeared. The children with ADHD who had similar intelligence levels to the control group looked at the puzzles in much the same way. This finding suggests that the less efficient strategy observed in the ADHD group was not a unique feature of the disorder itself, but rather a reflection of the lower average intelligence often associated with it.

There was one notable exception to this rule. Even when intelligence was taken into account, the children with ADHD still switched their gaze between the puzzle and the answers more often than the other children. This rapid switching, which the researchers measured as a frequency of attention shifts, persisted regardless of how smart the child was. This behavior aligns with a known characteristic of ADHD: a tendency for attention to fluctuate more than usual. It suggests that while the overall strategy of solving the puzzle is driven by intelligence, the specific rhythm of how attention is deployed—how often the mind jumps from one thing to another—may be a distinct trait of the disorder. The study also looked at pupil size, which can indicate how much mental effort a person is exerting. They found that pupil size did not explain the differences in strategy, reinforcing the idea that the core differences lay in how the children processed the visual information.

Ultimately, the study paints a picture of reasoning as a skill that develops with time and ability. For children with ADHD, the challenge in solving these puzzles appears to be linked to the same factors that influence their general intelligence. When they possess the cognitive tools to understand the task, they can adopt the same efficient, constructive strategies as their peers. The one lingering difference is in the rhythm of their attention, a tendency to shift focus more rapidly, which remains even when their reasoning ability is matched. This research does not suggest that children with ADHD cannot learn to solve problems effectively, but rather that their path to doing so may be influenced by the same cognitive resources that help everyone else. By watching where their eyes go, scientists have gained a clearer view of the invisible mechanics of thought, showing that the style of thinking is not a fixed trait of a diagnosis, but a fluid process shaped by age, ability, and the unique way each mind navigates the world.