Abstract
It is believed that the approximate estimation of large sets and the exact quantification of small sets (subitizing) are supported by two different systems, the Approximate Number System (ANS) and Object Tracking System (OTS), respectively. It is a current matter of debate whether they are both impaired in developmental dyscalculia (DD), a specific learning disability in symbolic number processing and calculation. Here we tackled this question by asking 32 DD children and 32 controls to perform a series of tasks on visually presented sets, including exact enumeration of small sets as well as comparison of large, uncountable sets. In children with DD, we found poor sensitivity in processing large numerosities, but we failed to find impairments in the exact enumeration of sets within the subitizing range. We also observed deficits in visual short-term memory skills in children with dyscalculia that, however, did not account for their low ANS acuity. Taken together, these results point to a dissociation between quantification skills in dyscalculia, they highlight a link between DD and low ANS acuity and provide support for the notion that DD is a multifaceted disability that covers multiple cognitive skills.
Highlights
Humans possess two basic non-verbal systems underlying the quantification of the number of objects in sets
Results indicated that dyscalculic children made significantly more errors and were slower than controls (main effect of group for accuracy: Mcontr = .97, SD = .02, Mdysc = .95, SD = .03; F(1,62) = 8.94, p = .004, η2G = .04; for RTs: Mcontr = 920.04 ms, SD = 238.26 ms; Mdysc = 1139.2 ms, SD = 321.49 ms; F(1,62) = 10.07, p = .002, η2G = .12), and that, for both groups, close numbers were more difficult to compare than distant numbers (main effect of distance for accuracy: F(7,434) = 57.04, p < .001, η2G = .4; for RTs: F(7,434) = 53.7, p < .001, η2G = .1)
Because this measure is dependent upon model fitting, we excluded the subjects for which the model did not fit well
Summary
Humans possess two basic non-verbal systems underlying the quantification of the number of objects in sets. One system allows approximate estimation ( called approximate number system, or ANS) and it generally follows the Weber law, according to which the threshold of number discrimination between two stimuli increases proportionally with the intensity of the stimuli, i.e. with the magnitude of the numerosities. Some authors have proposed that the discrimination threshold follows the Weber law only in the case of low-density numerosities, while for high-density and crowded numerosities a texture-like mechanism drives the numerosity comparison [1,2,3] (i.e., when the dots are too dense, numerosity judgements seem to be performed using a texture-based mechanism, evident from the fact that in those cases number discrimination threshold increases with the square root of numerosity instead of with its log).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
