Tokyo, Japan – Researchers at Tokyo Metropolitan University have uncovered intriguing insights into how numerical information in our vision affects our spatial awareness. By conducting experiments with volunteers, the team found unexpected biases in how participants perceived the center of lines and squares filled with numbers. This study highlights the complex interplay between “object-based” processing and numerical information processing in our perception of space.
The findings, led by Professor Masami Ishihara and doctoral student Ryo Hishiya, suggest that numbers in our vision can influence how we perceive the world in surprising ways. This phenomenon, known as spatial-numerical association, demonstrates how our brain’s processing of numbers can introduce “attentional biases.” For instance, in cultures with left-to-right writing systems, people tend to respond faster when lower numbers appear on the left side. This bias reverses with larger numbers, suggesting a deeply ingrained “mental number line.”
Exploring the Mental Number Line
Spatial-numerical association is not limited to numbers alone. It extends to any information indicating magnitude, such as brighter lights or louder noises. Remarkably, similar trends have been observed in animals and insects, indicating that a left-to-right mapping of magnitude-related information onto space might be a fundamental characteristic of nature. Understanding these biases is crucial not only for comprehending brain function but also for optimizing information presentation in various fields.
The research team employed “bisection tasks” to explore this association further. In these tasks, volunteers estimated the center of a line or bar. When smaller numbers were used, participants consistently placed the center more to the left than when larger numbers were used, confirming the left-to-right mental number line. However, when the experiment involved vertical bars, participants placed their point lower for larger numbers, contradicting the expected “bottom-to-top” association from previous studies. This suggests that more factors are at play than just the mental number line.
Breaking New Ground with Two-Dimensional Shapes
In a novel approach, the team extended their experiments to squares, or two-dimensional shapes. Surprisingly, the effect of number magnitude disappeared. Instead, the presence of numbers induced a strong upward bias and a weak leftward bias. In contrast, the absence of numbers led to a stronger horizontal bias, likely due to pseudoneglect, a natural bias in attention toward the left.
The researchers propose that this vertical bias reflects the influence of the ventral visual stream, the brain region responsible for object recognition, which tends to direct attention upward. In this scenario, “object-based” processing appears to have a more dominant effect than processing the numerical value itself.
Implications and Future Directions
While the study opens new avenues for understanding spatial perception, it also raises questions about the broader implications of these biases. The findings could have significant applications in fields such as design, education, and technology, where understanding how people perceive information can enhance user experience and information delivery.
Future research will likely delve deeper into the mechanisms underlying these biases and explore their potential applications. As Professor Ishihara notes, “Understanding the subtle asymmetries in our perception can lead to more effective ways of presenting information, ultimately improving how we interact with the world.”
The study from Tokyo Metropolitan University offers a fresh perspective on the intricate ways in which our brains process numerical information and spatial awareness. As researchers continue to unravel these complexities, the potential for practical applications in various domains becomes increasingly apparent.
