This action investigated number perception in individuals with and without dyscalculia by means of psychophysics, eye tracking and fMRI techniques. I found that humans can perform a saccadic eye movement toward the more numerous of two arrays at extremely high speed (only 190 ms) and that pupil size scales with the perceived numerosity of stimuli of identical luminance: pupil constriction and dilation (depending on stimulus luminance) were stronger for patterns with higher numerosity, physical or illusory. These studies suggest that numerosity is a salient and spontaneously detected visual feature that automatically attracts out attention. The observed numerosity-driven fast saccades and pupil modulation suggests that there might be a primitive circuitry that quickly transforms the numerosity information into oculomotor and pupillary responses. In collaborative studies, I also characterized the localization of the cortical areas supporting different aspects of numerical cognition (numerical perception, numerical operations, groupitizing and calculation) relative to anatomical and functional landmarks at high resolution, with 7T and 3T fMRI and multivariate pattern analysis. In addition, I carried out other behavioral studies in individuals with and without dyscalculia. These studies 1) characterized the phenomenon of groupitizing showing that it can be used as an efficient strategy to estimate visual and auditory numerosities; 2) tested how perception of time and number is affected by the distance between the observer and the stimulus, determining the possibility to act on it; 3) characterized visual perception in dyscalculia and found that dyscalculic individuals have excessive visual crowding which prevents them from efficiently segregating individual items in the periphery of the visual field, and impaired global shape perception which may prevent them from successfully group items together; 4) simulated some behavioral signs characterizing dyscalculics’ numerical perception in individuals without dyscalculia by loading participants’ visuo-spatial working memory, suggesting that a common system supporting both visuo-spatial working memory and numerical perception might be disrupted in dyscalculia; 5) explored another branch of mathematics, i.e. geometry, and how perception of geometrical sequences interacts with numerosity perception in primary school children. Altogether these findings contributed to advance the understanding of the mechanisms underlying numerical perception, how they relate to school achievement and to characterize visual perception deficits in dyscalculia.
The results of the action have been disseminated through 15 manuscripts, presentations at 5 conferences, 4 seminars to students at the University of Pisa and Florence, social media [accounts: @EliCastaldi (Twitter), elisa.castaldi.731 (Facebook), elisa-castaldi (LinkedIn)], press releases (e.g.
https://rb.gy/j05e01 https://rb.gy/forsmr
https://rb.gy/gbjuop https://rb.gy/5ufxjn) podcast (
https://rb.gy/q64xdk) and website.