This study introduces a new perceptual phenomenon known as bistability, which occurs when digital numerals are partially obscured. The experiment results suggest that this perception effect largely arises from mid-level visual processing, where complex shapes and number forms are interpreted.
Recognizing numerical characters, particularly Arabic numerals, is crucial in our everyday lives within contemporary society. Investigating the perceptual and neurological mechanisms that empower us to understand these characters is a significant scientific focus. In this research, scientists examined a bistable perceptual occurrence involving a specially designed character called the occluded digital numeral to gain insights into how we recognize numbers.
The digital numeral is a unique type of font designed for use in electronic devices, such as traffic countdown displays, digital calculators, and various LED panels. Occasionally, a partial blockage of these characters gives rise to a fascinating perceptual phenomenon whereby one numeral may be interpreted as having multiple, typically two, meanings. “Due to the simplistic nature of digital numerals, partial occlusion leads to visual uncertainties. In simpler terms, the visual information is inadequate for us to definitively interpret the obscured number,” explained Dr. Junxiang Luo from the National Institute for Physiological Sciences, the lead researcher of the project.
To further explore this phenomenon, the researchers conducted a behavioral experiment involving healthy participants who engaged in visual adaptation tasks. This experimental design aimed to assess how exposure to specific visual inputs influences perceptual bias. Notably, after prolonged exposure to standard digital numerals, participants reported that they perceived a distinct number, which was often different from the one they had adapted to.
“Visual adaptation effectively lowers the neural sensitivity in a specific visual processing stage for a certain type of visual input. By analyzing how much the interpretation shifts away from the bistable state following exposure to different visual stimuli, we can pinpoint the level at which numeral recognition occurs,” Dr. Luo stated.
The team selected a range of adaptation stimuli for their study. They found that the observed bistability is not influenced by low-level visual factors, such as basic features, nor by high-level factors like semantics. These findings imply that mid-level visual processing, which encodes intricate shapes and symbolic representations of numbers, plays a significant role.
The perceptual phenomenon identified in this psychophysical analysis offers opportunities for future physiological studies. Researchers aim to compare brain activity linked to different perceptual interpretations of the same occluded numerals. “Our goal is to extend this research using physiological methods to achieve a deeper understanding and more precise localization of the brain regions responsible for perceptual bistability,” Dr. Luo remarked.
The study’s findings were published in the Journal of Vision on September 17th, 2024. Dr. Isao Yokoi, Professor Hiromasa Takemura from the National Institute for Physiological Sciences, and Dr. Serge Dumoulin from the Spinoza Centre for Neuroimaging also contributed to this research.
