Measuring the Diversity of Qualia: Category-Theoretic Indices for Psychophysical Experimental Data
F1000Research June 25, 2026 Kyoko Kusano, Hayato Saigo, Naotsugu Tsuchiya
Measuring the diversity of subjective experiences (qualia) is difficult. A new mathematical approach, derived from category theory, offers two indices—'generalized magnitude' and 'spread'—to quantify how varied a person's internal structure of sensations is. In an experiment with 120 participants who rated similarities among color and emotion words, both indices captured differences in qualia structures at the group and individual levels. The indices also reveal complex graphical features of these structures, providing a principled way to compare how diverse people's inner experiences are.