Girls as young as 8 show cognitive sensitivity to their own body weight, new study finds

A new study has found that girls as young as eight or nine years old already have a tendency to notice and respond to numbers representing their own body weight, in ways that are different from boys. When these girls were shown a number referring to their weight, their attention was drawn to it and it distracted them from other visual information. This was not the case for boys, suggesting that an awareness of one’s body weight develops differently for girls and appears surprisingly early in childhood. The findings were published in Experimental Brain Research.

Previous research has shown that infants can recognize when a person’s body is shaped in an expected or unexpected way and can sense when a touch is happening to their own body. Newborns can even tell when a visual and a tactile signal match, and this ability improves as children get older. Yet very little is known about when and how children begin to understand abstract ideas about their bodies, such as their weight. This study aimed to shed light on that process.

The researchers wanted to test if knowing one’s own body weight influences attention, especially in children. Body weight is a measure that many people become aware of early in life. In Japan, where this study was conducted, children have regular health checkups in schools, making weight an important number that many children recognize. The researchers wondered if seeing this number would automatically capture a child’s attention and if this effect would be different for girls and boys.

“Our interest was driven by growing public health concerns surrounding childhood obesity and its potential impact on cognitive development. While many studies have examined physical health outcomes, we were particularly interested in understanding how body weight might relate to attentional processes in children—a relatively under explored area,” said study author Shuma Tsurumi, an assistant professor of psychology at Hokkaido University.

The team conducted an experiment with 44 Japanese children between the ages of eight and nine. The group was balanced with an equal number of girls and boys. All of the participants had normal or corrected-to-normal eyesight and were able to recognize both their own weight and the Latin alphabet. Before starting, the researchers confirmed with the children and their parents that the children knew their weight and were comfortable identifying letters.

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Each child participated in a computer-based test called a rapid serial visual presentation task. The test involved focusing on a stream of letters that appeared quickly one after another. Among these letters was a target letter, and the child’s goal was to identify which letter was presented. Occasionally, right before the target appeared, the researchers inserted a number — sometimes a number representing the child’s own body weight, and sometimes a neutral number unrelated to the child. The researchers varied the time gap between this number and the target letter, using a short gap of 200 milliseconds and a longer one of 800 milliseconds.

If the number captured the child’s attention, it would interfere with their ability to identify the target quickly and accurately. The researchers measured this by looking at how often the child correctly identified the target.

The researchers observed a notable difference between girls and boys. Girls were less accurate when the number representing their body weight appeared just before the target, regardless of the time interval. In other words, their own weight distracted them from focusing on the task. The neutral number had no such effect. In contrast, boys were equally accurate regardless of whether the number shown was their weight or not.

This finding suggests that girls at this age already have a stronger internal link between their attention and their own body weight. Girls also tend to have more body awareness and are better at estimating their own body size compared to boys. Other studies have found that girls of this age often have higher levels of body dissatisfaction, and this might make weight a more meaningful piece of information for them. These differences could potentially be the starting point for the well-documented focus that adolescent girls and adult women have on their body image.

The effect lasted for both short and long delays between the number and the target letter. This means that the girls’ attention was captured by the number for an extended period of nearly a second. Similar long-lasting attention effects have been observed in clinical studies with people who have obsessive-compulsive tendencies or addiction, suggesting that highly relevant or triggering information can dominate attention beyond the usual time span.

“We were surprised to find that simply presenting a numerical value representing body weight was enough to capture children’s attention,” Tsurumi told PsyPost. “This suggests that, for some children—especially girls—body weight may serve as an important marker, one that they are attuned to either consciously or unconsciously. It raises the possibility that even at a young age, children may already be sensitive to weight-related cues. This may help explain, in part, why eating disorders are more prevalent among females, as weight becomes a salient psychological concern early in development.”

“Notably, these differences were most evident in children under the age of 10. This suggests that the relationship between attention and factors like body weight may emerge early in development and may differ by gender, highlighting the importance of considering age and sex when examining cognitive processes in childhood.”

Although the study provides valuable insights, it has some limitations. The researchers only tested a narrow range of ages — eight and nine years old. “While we observed the effect in this specific developmental period, it remains unclear when exactly these attentional differences first emerge and how long they persist,” Tsurumi noted. “Future research will be needed to track these patterns across a wider age span.”

“We hope to continue exploring how physical health factors—such as body weight, sleep, and physical activity—interact with cognitive development in children. We believe that this line of research can contribute to a more integrated understanding of child development. By bridging cognitive science and health research, we hope to encourage more holistic approaches in education and pediatric care.

The study, “Body weight and attentional capture in children,” was authored by Shuma Tsurumi, So Kanazawa, Masami K. Yamaguchi.