Numerical cognition is resilient to dramatic changes in early sensory experience

Abstract

Humans and non-human animals can approximate large visual quantities without counting. The approximate number representations underlying this ability are noisy, with the amount of noise proportional to the quantity being represented. Numerate humans also have access to a separate system for representing exact quantities using number symbols and words; it is this second, exact system that supports most of formal mathematics. Although numerical approximation abilities and symbolic number abilities are distinct in representational format and in their phylogenetic and ontogenetic histories, they appear to be linked throughout development--individuals who can more precisely discriminate quantities without counting are better at math. The origins of this relationship are debated. On the one hand, symbolic number abilities may be directly linked to, perhaps even rooted in, numerical approximation abilities. On the other hand, the relationship between the two systems may simply reflect their independent relationships with visual abilities. To test this possibility, we asked whether approximate number and symbolic math abilities are linked in congenitally blind individuals who have never experienced visual sets or used visual strategies to learn math. Congenitally blind and blind-folded sighted participants completed an auditory numerical approximation task, as well as a symbolic arithmetic task and non-math control tasks. We found that the precision of approximate number representations was identical across congenitally blind and sighted groups, suggesting that the development of the Approximate Number System (ANS) does not depend on visual experience. Crucially, the relationship between numerical approximation and symbolic math abilities is preserved in congenitally blind individuals. These data support the idea that the Approximate Number System and symbolic number abilities are intrinsically linked, rather than indirectly linked through visual abilities.

Enhanced performance on a sentence comprehension task in congenitally blind adults

“…However, for many math tasks, including those that activate "visual" cortex in blindness, there are no blindness-related advantages (e.g. Crollen et al, 2019, Kanjlia et al, 2016, Kanjlia et al, 2018). In the current study, the blind group performed no different from the sighted on a timed subtraction task and less well than the sighted on a timed division task.…”

Neural basis of approximate number system develops independent of visual experience

“…Congenitally blind individuals show similar or slightly better performance than sighted individuals when estimating numbers of tones, footsteps or finger taps, and performance is ratio-dependent in both groups . Prior studies also find that, like people who are sighted, individuals who are congenitally blind recruit the IPS during symbolic number reasoning and show similar behavioral correlations between numerical approximation and symbolic math performance across individuals (Amalric et al, 2017;Crollen et al, 2019;Kanjlia, Feigenson, et al, 2018;Kanjlia et al, 2016). Together, these findings suggest that numerical representations are established in the IPS independent of gross differences in sensory experience.…”

Effects of Visual Training of Approximate Number Sense on Auditory Number Sense and School Math Ability

“…However, evidence suggests that children presented with difficult approximate numerical discriminations perform better when presented with redundant visual and auditory input, compared to only visual input, suggesting that auditory tones are not simply treated as indicating the presence of visual objects ( Posid and Cordes, 2019 ). Furthermore, people blind from birth succeed at purely auditory ANS tasks ( Kanjlia et al, 2018 ), showing that ANS representations can be generated in the total absence of any visual experience. Still, despite the above findings, it is impossible to entirely rule out an account by which visualization plays some role in the processing of auditory input – something that is currently the topic of much ongoing debate ( De Volder et al, 2001 ; Amedi et al, 2005 ; Vetter et al, 2014 ).…”

“…The third aim was to ask whether the link between ANS precision and school math abilities reflects individual differences in an abstract, modality-neutral sense of approximate number, or if instead the correlation is explained entirely by a link between math and visuospatial abilities (i.e., subsymbolic-symbolic transfer). Kanjlia et al (2018) found that ANS precision for auditory sequences correlated with math performance in blind and sighted adults. But, it remains unknown whether there is a visually independent link between the ANS and math ability early in development.…”

“…Visual and auditory numerical approximations also appear to activate the same fronto-parietal brain networks in adults ( Piazza et al, 2006 ), and the same groups of neurons have been found to encode auditory and visual numerosity in monkeys ( Nieder, 2012 ). And, in the total absence of visual experience, completely normal ANS functioning remains intact in audition in congenitally blind individuals who have never processed number visually ( Kanjlia et al, 2018 ).…”