Department of Neurology, Milton S. Hershey Medical Center and Penn State College of Medicine.
Department of Neural & Behavioral Sciences, Milton S. Hershey Medical Center and Penn State College of Medicine.
Cogn Sci. 2022 Sep;46(9):e13189. doi: 10.1111/cogs.13189.
Synesthetes can be distinguished from nonsynesthetes on a variety of experimental tasks because their concurrent synesthetic experiences can affect task performance if these experiences match or conflict with some aspect of the stimulus. Here, we tested grapheme-color synesthetes and nonsynesthetic control participants using a novel perceptual similarity task to assess whether synesthetes' concurrent color experiences influence perceived grapheme similarity. Participants iteratively arranged graphemes and, separately, their associated synesthetic colors in a display, such that similar items were placed close together and dissimilar items further apart. The resulting relative inter-item distances were used to calculate the pair-wise (dis)similarity between items in the set, and thence to create separate perceptual representational dissimilarity matrices (RDMs) for graphemes and colors, on an individual basis. On the assumption that synesthetes' similarity judgments for graphemes would be influenced by their concurrent color experiences, we predicted that grapheme and color RDMs would be more strongly correlated for synesthetes than nonsynesthetes. We found that the mean grapheme-color RDM correlation was indeed significantly higher in synesthetes than nonsynesthetes; in addition, synesthetes' grapheme-color RDM correlations were more likely to be individually statistically significant, even after correction for multiple tests, than those of nonsynesthetes. Importantly, synesthetes' grapheme-color RDM correlations were scaled with the consistency of their grapheme-color associations as measured by their Synesthesia Battery (SB) scores. By contrast, the relationship between SB scores and grapheme-color RDM correlations for nonsynesthetes was not significant. Thus, dissimilarity analysis quantitatively distinguished synesthetes from nonsynesthetes, in a way that meaningfully reflects a key aspect of synesthetic experience.
联觉者在各种实验任务中可以与非联觉者区分开来，因为他们的并发联觉体验如果与刺激的某些方面匹配或冲突，可能会影响任务表现。在这里，我们使用一种新的知觉相似性任务来测试字母-颜色联觉者和非联觉控制参与者，以评估联觉者的并发颜色体验是否会影响感知的字母相似性。参与者迭代地在显示器中排列字母和它们的关联联觉颜色，使得相似的项目放在一起，而不相似的项目则更远。由此产生的相对项目间距离用于计算集合中项目之间的成对（不）相似性，然后为每个参与者分别创建字母和颜色的单独知觉表示差异矩阵（RDM）。基于联觉者对字母的相似性判断会受到其并发颜色体验的影响的假设，我们预测联觉者的字母和颜色 RDM 之间的相关性会比非联觉者更强。我们发现，联觉者的平均字母-颜色 RDM 相关性确实明显高于非联觉者；此外，即使在进行多次测试校正后，联觉者的字母-颜色 RDM 相关性也更有可能在个体上具有统计学意义，而非联觉者则不然。重要的是，联觉者的字母-颜色 RDM 相关性与他们的 Synesthesia Battery (SB) 分数所衡量的字母-颜色关联的一致性成正比。相比之下，非联觉者的 SB 分数与字母-颜色 RDM 相关性之间的关系并不显著。因此，差异分析以一种有意义地反映联觉体验关键方面的方式定量地区分了联觉者和非联觉者。
