How visual is the “groupitizing”? The impact of visual deprivation over its emergence.

Previous research suggests that participants can enumerate a set of objects more quickly and precisely when clusters can be formed according to Gestalt factors. This effect is known as "groupitizing". Although predominantly observed in the visual domain, the role of visual experience in its development is still unknown. Has groupitizing emerged from neural mechanisms underlying grouping-cues processing in the early visual cortex? What is the impact of visual deprivation on its development? A fundamental model to investigate these questions is to study congenitally blind (CB) individuals. Lacking experience of visual grouping cues, CB individuals should not develop groupitizing strategies if vision is essential. Conversely, if vision is not mandatory, CB individuals should reveal groupitizing abilities in other sensory modalities. Importantly, visual deprivation could prompt compensatory cognitive abilities, such as better auditory working memory, which may influence the enumeration of auditory stimuli. We compared congenitally blind and sighted individuals in an auditory groupitizing task, where participants estimated the number of pure tones (5 to 12) presented rapidly, which were randomly interspaced (ungrouped condition) or grouped by temporal proximity (grouped condition). We found that grouped sequences yielded lower error-rates and higher precision compared to ungrouped ones in both blind and sighted participants. Overall, the blind group presented lower error-rates and slightly better numerical precision, with a greater grouping-benefit toward larger set sizes, compared to sighted participants. These findings suggest that groupitizing may emerge even without vision, potentially relying on perceptual amodal mechanisms, and that visual deprivation may boost groupitizing in the auditory modality.