How often a preschooler blinks may offer a clue about how their ability to control themselves and switch between tasks is developing. That is the conclusion of the authors of a new study published in the journal Communications Psychology. It turned out that children who blink more often perform better on a test of mental flexibility, and show more pronounced activity in the brain area behind the forehead.
This concerns so-called executive functions - a set of higher mental skills that allow a person to hold information in mind, resist distractions and flexibly switch between different rules or goals. These abilities develop rapidly between the ages of three and six and are linked to future academic performance, social adaptation and health. This growth is thought to reflect the maturation of the prefrontal cortex - the outer layer of the brain located at the front of the head, directly behind the forehead.
The study involved 113 Japanese children aged 35 to 80 months (average 59 months; 55 girls and 58 boys) from two kindergartens in Osaka and Kyoto. The scientists measured the rate of spontaneous blinking - how many times per minute a person blinks on their own, without an external stimulus. For this they used a video recording at 30 frames per second; two trained raters counted blinks in 112 children whose eyes were visible.
At the same time, the children played the Dimensional Change Card Sort card game, in which cards must be sorted first by color, then by shape, and then by an alternating rule. Switching accuracy was assessed as the percentage of correct responses in trials where the rule changed. Brain activity was measured using functional near-infrared spectroscopy (fNIRS) - a non-invasive method in which a band with sensors is placed on the forehead, shining safe light through the skin and detecting changes in blood oxygen.
The results showed that children with a higher blink rate coped better with switching rules (correlation 0.35). A correlation is a statistical relationship that by itself does not prove causation. After adjusting for age, the relationship remained (partial correlation 0.22). It was also found that in older children, activity in the right dorsolateral prefrontal cortex (the upper-lateral area) was higher and positively correlated both with blink rate (0.27) and with switching accuracy (0.32). After accounting for age, these relationships persisted (0.21 each).
The authors emphasize that the findings are correlational and the study is cross-sectional, so it cannot be said that blinking or brain activity directly causes improved mental flexibility. In addition, blink rate depends on many factors, including neurotransmitters such as acetylcholine and norepinephrine, not only dopamine. The scientists caution against using this measure to assess or diagnose individual children.
"Blinking may become one of the indicators of executive function development," the authors noted. "But this is a group tendency, and the relationship is not strong enough to accurately assess a specific child." They also plan to study how lifestyle, genetics and the environment influence these relationships.