Counting on your senses

We have a sense of what is one thing, one object, or one event. This sensation of “one” can be defined in various sensory modalities. We can see one bird, feel one coin, or hear one beep. This means that we should be able to judge numerosity in each of these modalities. When numerosity is hard to judge in one modality, we might choose to do it in another. In the Short & Sweet section of this special issue, Anstis will argue that Gallileo’s proposal to use touch and hearing for counting when vision fails exemplifies the very first documented form of sensory substitution. We hypothesize that number information is processed in a largely modality independent way. To investigate this hypothesis, multisensory research on numerosity perception is needed. At the moment, most research on numerosity perception has been done in vision. As more studies on numerosity judgment in other modalities as well as cross-modal studies emerge, the similarities and differences between the modalities will become clearer. We initiated this special issue to draw attention to this research topic and to hopefully help it gain momentum. The usefulness of multimodal studies in numerosity perception is highlighted in a review by Anobile, Cicchini, and Burr in this special issue. One of the topics they discuss is perceptual adaptation to numerosity and how perceptual aftereffects of exposure to a certain quantity can transfer between modalities. This suggests that “three-ness” or “ten-ness” could be a perceptual property of a set and that this information is shared between modalities. The remainder of this special issue contains a series of empirical studies on various aspects of numerosity perception in vision, touch, and audition. We will introduce each of them below