Comparing color qualia structures through a similarity task in young children versus adults

Abstract

Examination of the subjective qualitative aspects of an experience, or "qualia" in short, is a fundamental and core aspect of consciousness research. How can we characterize the particular quality of redness, i.e. a red quale? Based on a recent proposal of the structural characterization of qualia, which did not rely on verbal descriptions, we developed a task that obtained pairwise similarity judgments at four graded levels, with easy and intuitive visual interfaces designed to engage young children. We examined color qualia structures in children (3 to 12-y-old in Japan and 6 to 8-y-old in China) and compared these with those of Japanese adults. Approximately half of the assessed 3-y-old children completed the experiment via our touch panel device version of the task and had reliable responses. Despite known developmental and/or cultural effects of color term usage, we found that color qualia structures were quite similar across the age groups and cultures. Our finding supports the view that color qualia structures emerge early. We also observed age-related differences in the evaluations of some color pairs, which implied subtle changes in the structures behind color experience.

Keywords: children; color; consciousness; development; qualia.

Fig. 1.

Qualia structure approach. (A) Participants evaluate the similarity of a briefly presented (500 ms) paired stimuli using four levels (very similar, slightly similar, slightly dissimilar, and very dissimilar). (B) Results are compiled into a similarity matrix. (C) Similarity ratings are used to infer and visualize the underlying qualia structure via multidimensional scaling (MDS). (D) Transformation techniques are used to assess the equivalence of qualia structures between two individuals or groups. (E) This study aims to characterize the developmental trajectory of qualia structure (from 3-y-old children to adults) within one culture and compare them in another culture. (F) A child with the touch panel used in Experiments 2 to 4. We conducted Experiment 1 via computers. (G) Percentage of “very dissimilar” or “very similar” responses in each experiment. (H) Double-pass correlation to assess the reliability of participants’ responses. For additional details, SI Appendix, Supplemental Analysis.

Fig. 2.

(A) Group mean dissimilarity matrices for each age group. White and dark cells represent high similarity and dissimilarity, respectively. (B) 2-dimensional MDS representation in each age group across the four experiments. Colors of the symbols are similar to the ones used for the experiment. Different shapes correspond to different age groups and cultures (see the legend on the Right).

Fig. 3.

(A) Correlation coefficients of an individual similarity matrix within and between the groups after excluding outliers (before exclusion, see SI Appendix, Fig. S2). This “meta” similarity matrix’s entries quantify the similarity between a similarity matrix of one person to that of another. The diagonal red line represents the correlation between a given individual’s similarity matrix and itself, which is always 1. The color of each matrix entry indicates a Spearman’s correlation coefficient, with red to blue between 1.0 to 0.5. Gray lines separate participants according to their age. (B) Group differences of Mean Coefficient with Adults (MCwA) across groups. One dot represents an individual’s mean correlation coefficients with all the adult participants. The red regression line starts from age three and extends up to age 12 and adults (using a mean age 21). MCwA for adults were computed by removing the self-correlation (see the main text).

Fig. 4.

(A) Examples of age-related changes of similarity ratings to specific color pairs. (B) Age effects on the similarity of color pairs, defined as the magnitude of the slope for the age factor in the multiple regression analyses. Reddish cells indicate positive slopes, where older children rated color pairs as more similar. Purplish cells indicate negative slopes, where younger children rated color pairs as more similar. *represents cells with significant (P < 0.05/45 after Bonferroni corrections) age effects. (C) Schematic representation of the effect of age on similarity of color pairs. Reddish and purplish arrows represent significant positive and negative slopes, respectively, as in B.