ino and Marks (2001) suggested that the crossmodal associations in weak synesthesia are systematic and contextual, whereas those in strong synesthesia are systematic and absolute (see also Marks, 2013; Marks and Mulvenna, 2013).
Therefore, one possible reason for the discrepancy between our results and the results of previous studies might be that these taste-shape correspondences depend to some degree on the particular shapes that are presented and on the total number of shapes presented. For example, it was the marketers of last couple of decades who taught the Western world about the associations between the limpid electric blue and the sweet raspberry taste/flavor (Shankar et al., 2010). A similar discrepancy has also been observed in the literature of odor-shape correspondences. On one hand, Hanson-Vaux et al. (2013) had their participants match 20 odors with a pair of shapes which were often used to elicit the Bouba–Kiki effect. Their results revealed that the lemon and pepper odors were associated with the angular shape, whereas the raspberry and vanilla odors were associated with the round shape, indicating a Bouba–Kiki effect in the odor-shape associations. On the other hand, Seo et al. (2010) asked their participants to match eight odors with 19 irregular shapes (which were referred to as abstract symbols in their paper). Interestingly, the results revealed that pleasant odors were associated with circular or curved shapes, whereas unpleasant shapes were associated with square or angular shapes instead. It is difficult to directly compare the findings in these two studies, as different shapes were used. However, it should be noted that when a large range of varied shapes were used, the more global features (e.g., whether a shape is circular or angular) influences which odors were associated with them. Similarly, when only a blob and an asymmetric star shape, or two categories of round and sharp shapes (see Deroy and Valentin, 2011), were presented, the sharp vs. round difference between them may be signified. By contrast, when a greater number of shapes (15 in the present study) were presented, the sharp vs. round difference might be less salient. That is, when being compared to a lot regular shapes such as a square, rectangle, and so on, the blob and asymmetric star shapes might be classed into one category of irregular shapes. We are currently conducting research to try to understand this issue.
In conclusion, the findings of the present study highlight a number of interesting crossmodal correspondences between four of the tastes (bitter, salty, sour, and sweet) and certain visual features (colors, shapes, and textures). These findings also reveal some cross-cultural similarities and dissimilarities in these correspondences, thus implying the different natures of the different correspondences. That is, some crossmodal correspondences may be more subject to people’s cultural background than others. Future research is needed to test the underlying neural mechanism of the crossmodal correspondences (also see Seo et al., 2010; Chan et al., 2014).
Each of the listing co-authors made the following contributions to the paper: Charles Spence, Andy T. Woods, Kirsten J. McKenzie, and Xiaoang Wan co-developed the idea for the study and collaboratively designed the study. Andy T. Woods, Xiaoang Wan, and Kirsten J. McKenzie collected the data. Jasper J. F. van den Bosch conducted the data analysis. Jasper J. F. van den Bosch, Andy T. Woods, Xiaoang Wan, Carlos Velasco, and Charles Spence conducted the interpretation of the data. Xiaoang Wan, Charles Spence, Andy T. Woods, Carlos Velasco, and Jasper J. F. van den Bosch drafted the manuscript. All of the authors have read and approved the final version of the manuscript.
Conflict of Interest Statement
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
This research was supported by National Natural Science Foundation of China (Grant No. 71472106) awarded