The new preprint, co-authored by Mr. Togashi and Prof. Oizumi of Planning Group C01, Dr. Hiramatsu of the Publicly Offered Research Group, and Prof. Tsuchiya of Planning Group A01, has been published! 

 We present the first empirical evidence supporting that "my red" is "your red", through an unsupervised alignment of color qualia structures at the individual level. 

 By collecting a massive dataset of 4,371 similarity judgments of 93 colors from each of the participants, we empirically constructed individual color qualia structures. This unprecedentedly rich dataset enables us to directly address the original question.

 The key method is an unsupervised alignment of qualia structures. Our method finds the optimal, maximally structure-preserving correspondence between color experiences across individuals, without presupposing any fixed mapping, such as your “red" should correspond to my “red”.

 We demonstrate that, among certain individuals, color qualia structures of four participants can be “correctly” aligned in an unsupervised manner. That is, "my red" corresponds to "your red" not by assumption, but because it represents the optimal mathematical mapping.

 Importantly, this structural correspondence constrains the plausibility of the longstanding “inverted qualia” argument in philosophy: if my red were your green, the relational geometries would be incompatible, and our algorithm would not have identified such precise alignment.

 Crucially, however, this structural alignment is not universal. Indeed, we identified two distinct aligned clusters, corresponding to color-neurotypicals and atypicals. Moreover, we discovered "structural intermediates": individuals who do not robustly align with either cluster.

 Together, these findings point toward a novel "structure-based taxonomy" of divergent experiences, grounded directly in phenomenology.  Our results open up a new avenue to quantitatively assess the commonality and individuality of subjective experiences.

 For more details, please check out our preprint and a 1-minute explanatory video:

 Preprint (bioRxiv): https://biorxiv.org/content/10.64898/2026.02.13.705699v1.article-info

 1-minute video: https://www.youtube.com/watch?v=6MCVo7SsdoI

Paper Information

Authors:  Yu Togashi, Yuko Yotsumoto, Chihiro Hiramatsu, Naotsugu Tsuchiya, Masafumi Oizumi

Title: Robust individual alignment of color qualia structures: toward a structure-based taxonomy of divergent color experiences

Journal: bioRxiv 2026.02.13.705699  *This article is a preprint and has not been certified by peer review.

DOI: https://doi.org/10.64898/2026.02.13.705699

Abstract

 Whether qualitative aspects of consciousness, or qualia in short, are equivalent across individuals is a foundational scientific question. Testing this is challenging because one cannot assume a shared mapping between stimuli and private experience (my "red" may be your "green"). Previously, we proposed a structural characterization of qualia and the quantitative assessment of structural correspondences through an unsupervised alignment method, which does not presuppose such correspondence. Using this approach, our previous work focused on identifying optimal mappings between relational structures of color qualia at the group level. Given known perceptual diversities, however, it remained unknown whether any two individuals' structures could be empirically aligned. Here, we resolve this by collecting 4,371 pairwise similarity ratings for 93 colors from 11 individuals, enabling direct individual-to-individual alignment. We reveal two fundamental, coexisting features. First, we identified two clusters of individuals showing robust within-cluster alignment, corresponding to color-neurotypicals and atypicals. Second, we uncovered a continuous spectrum of diversity: some participants who showed normal color discrimination ability in terms of the Total Error Score (TES) on Farnsworth-Munsell 100 hue test nevertheless failed to align with either cluster, revealing idiosyncratic structures that defy simple categorization. Together, these findings suggest a novel structure-based taxonomy of divergent color qualia that complements conventional performance-based classification. Our method is generalizable to other sensory modalities, and opens a path to the scientific investigation of both shared and idiosyncratic qualitative aspects of consciousness.