Synesthesia for Color Is Linked to Improved Color Perception but Reduced Motion Perception

Abstract

Synesthesia is a rare condition in which one property of a stimulus (e.g., shape) triggers a secondary percept (e.g., color) not typically associated with the first. Work on synesthesia has predominantly focused on confirming the authenticity of synesthetic experience, but much less research has been conducted to examine the extent to which synesthesia is linked to broader perceptual differences. In the research reported here, we examined whether synesthesia is associated with differences in color and motion processing by comparing these abilities in synesthetes who experience color as their evoked sensation with nonsynesthetic participants. We show that synesthesia for color is linked to facilitated color sensitivity but decreased motion sensitivity. These findings are discussed in relation to the neurocognitive mechanisms of synesthesia and interactions between color and motion processing in typical adults.

Color synesthesia improves color but impairs motion perception

“…The data indicate that synesthetes had reduced motion sensitivity (i.e., higher coherence thresholds) compared to non-synesthetes. A, B & D: adapted with permission [1]. …”

“…In a recent paper, Banissy and colleagues [1] examined whether color synesthesia influences basic feature level perception in the absence of inducing stimuli. They found that synesthetes who experience color as their evoked sensation (concurrent) are better at discriminating color than non-synesthetes.…”

“…These findings are interesting because much extant research on synesthesia has focused on validating the phenomenon, investigating its origins or examining how synesthetic experiences interact with other perceptual and cognitive functions [3]. In contrast, few studies have examined how mechanisms underlying synesthesia may influence basic visual processes [1] let alone those unrelated to the synesthesia.…”

“…Research applying transcranial magnetic stimulation in neurotypicals suggests that brain regions involved in motion and color processing (i.e., hMT+ and hV4, respectively) can mutually inhibit one another [5]. Banissy and colleagues reason that the impaired motion perception observed in the color synesthetes may be an indirect consequence of a synesthesia-induced bias towards color in the interaction between color and motion processes [1]. A similar argument was used to explain the authors’ recent finding that form and color-processing areas (i.e., hV4) in the brains of color synesthetes had increased gray-matter volume compared to non-synesthetes.…”

“…If the current results indeed arise due to a competition between brain regions that process color and motion, then the same logic may predict anyone with particularly good color perception to have somewhat impaired motion perception. For example, their Table 1 shows that ‘Controls 6, 9 and 10’ have relatively high motion-coherence thresholds, on par with those in the synesthete group [1]. Do these non-synesthetes also have particularly good color perception—on par with that of the synesthetes?…”