For centuries, scientists and philosophers have pondered the nature of sensory perception. How do we experience colors, sounds, and tastes? More importantly, do we all perceive them in the same way? The question of whether two people see the same color red, for example, has remained an unsolved mystery. While subjective perception makes it impossible to provide definitive proof, a team of researchers from The University of Tokyo and Monash University in Australia has explored a novel approach to addressing this long-standing debate. Their study, published in the journal iScience, employs what they call a qualia structure paradigm to assess whether sensory experiences are intersubjectively equivalent.
At the heart of their research is the concept of qualia—a philosophical term used to describe subjective sensory experiences. Qualia encapsulate the idea of personal perception, such as how one feels when asked, “What is it like for you to experience a certain color?” The researchers recognized that while it is impossible to directly compare personal experiences, they could analyze structural similarities in perception across individuals. If people consistently group colors in similar ways, this might indicate that their perceptual experiences are at least highly comparable.
To test this idea, the team designed an experiment where volunteers were asked to rate the similarity of 93 different colors based solely on their perception, without relying on pre-existing color labels or categories. This approach ensured that participants’ judgments were based on raw visual experience rather than learned associations or language-based interpretations. The researchers then analyzed the data to compare how different individuals related one color to another.
The findings were striking. Despite the highly subjective nature of sensory perception, the participants demonstrated remarkable consistency in how they grouped and compared colors. This suggests that while we may never be able to step into another person’s mind, there is strong evidence that most people likely experience colors in a fundamentally similar way. Even individuals with the same type of color blindness showed structural similarities in their perception, supporting the idea that color experiences might be more universal than previously assumed.
However, the researchers were careful to acknowledge the limitations of their study. Their experiment does not definitively prove that all individuals perceive colors identically—only that their perceptual structures align to a significant degree. Factors such as genetic differences, neurological variations, and past experiences could still introduce subtle distinctions in perception.
This research has profound implications beyond color perception. If a similar qualia structure paradigm could be applied to other sensory experiences—such as taste, sound, or even pain—it could reshape our understanding of how humans process the world. It may also offer insights into conditions such as synesthesia, where people experience cross-modal sensory perceptions, like “hearing” colors or “seeing” sounds.
Furthermore, this study contributes to the growing field of neuroengineering and artificial intelligence. By understanding how humans structure sensory data, scientists could develop more accurate models of human perception for AI and robotics, paving the way for machines that process sensory information in a human-like manner.
In the broader philosophical landscape, this research offers a fresh perspective on the hard problem of consciousness, a term coined by philosopher David Chalmers. The study suggests that while we may never truly “know” another person’s experience, we can at least measure the likelihood of shared perceptual structures. This challenges extreme subjectivist views, which argue that perception is entirely personal and unquantifiable.
More information: Genji Kawakita et al, Is my “red” your “red”?: Evaluating structural correspondences between color similarity judgments using unsupervised alignment, iScience (2025). DOI: 10.1016/j.isci.2025.112029