e-Patterns Across the Four Groups
First, we visualized the associations between each stimulus and the five basic tastes in Figure 3, and performed Chi-square tests in order to see whether certain taste(s) were more often associated with one taste than the others. As can be seen in Table 2, all the colors except blue were associated with certain taste(s). The results of post hoc Chi-square tests revealed that some colors were certainly more strongly associated with one taste than with other tastes, including black with bitter, green with sour, pink with sweet, and white with salty.
FIGURE 3. The taste-patterns for each color (upper panel), each shape (lower panel), and each texture patch (on the right of the upper panel). Note that the percentage of the bitter, salty, sour, sweet, and umami taste terms chosen for the visual stimuli are represented by the fill-in colors black, white, green, pink, and blue, respectively.
TABLE 2. Results of Chi-square tests for each stimulus by all four groups of participants (N = 428).
As can be seen in Table 1 where the results of this study and two previous studies are summarized, some of our results are consistent with those reported by previous research, such as the white-salty associations (O’Mahony, 1983; Koch and Koch, 2003), and green-sour (Koch and Koch, 2003; Tomasik-Krótki and Strojny, 2008). By contrast, the crossmodal associations consistently observed in these three previous studies, i.e., the red-sweet and yellow-sour associations, failed to reach significance in the present study.
What is more, all of the shapes except the Arrow and Drop were associated with certain taste(s). The results of post hoc Chi-square tests revealed that some shapes were more strongly associated with one taste than the others, including cross/rectangle/square with bitter, and cloud/heart/star with sweet. The results also revealed that both the smooth and rough texture patches were strongly associated with the salty taste.
After weighting all the data by the participants’ confidence ratings as described in the Methods section, a MDS was calculated for all the colors and for all the shapes, respectively (see Figure 4). The results of the MDS are consistent with what was found with the Chi-square tests. This figure clearly shows that black, green, pink, and white are situated far away from each other in the MDS, consistent with the results of the Chi-square tests that they are strongly associated with four different tastes. On the other hand, the MDS figure shows one close cluster comprising the cloud, heart, and stars, and another tightly distributed cluster consisting of the cross, rectangle, and square. These results are consistent with the results of the Chi-square tests that cross, rectangle, and square are associated with bitter, whereas the cloud, heart, and star are associated with sweet instead.
FIGURE 4. Multi-dimensional scaling of distances among colors (upper panel) and shapes (lower panel). The thumbnails of the targets (color patches in the upper panel and shapes in the lower panel) were arranged in the way that their distance between each other reflects their dissimilarity in taste-patterns. Data from all countries combined, weighted by the confidence rating.
Cross-Cultural Similarities and Differences in the Taste-Patterns
In order to examine the cross-cultural difference in the taste-patterns, we first performed a log-linear analysis, using Stimulus (28 color-, shape-, and texture-stimuli) × Taste (bitter, salty, sour, sweet, and umami) × Country (China, India, Malaysia, and the USA) as the variables. The final model retained all effects. The likelihood ratio of this model was χ2(0) = 0, p = 1.00, indicating that the 3-way interaction of Stimulus × Taste × Country was significant, χ2 = 860.34, p < 0.001. In order to interpret this term, we then performed 2-way log-linear analyses for each stimulus with Taste and Country as variables. As can be seen in Table 2, the interaction between Taste and Country was significant for eight of the colors (blue, green, gray, orange, purple, red, wh