“…Benussi had already started exploring this topic while working at the University of Graz, approximately from 1908 (Antonelli, 2018;Bobbio & Giora, 2019;Bobbio & Roncato, 2023). In Padua, he handed over the investigation on the perception of numerosity to De Marchi around 1922, similar to what he had done with the stereokinetic effect, which was described by Benussi around 1918 and later assigned to Musatti (Bobbio & Giora, 2023;Giora & Bobbio, 2022;Musatti, 1924Musatti, , 1975. A recent review of stereokinetic phenomena is in Zanforlin (2017).…”