Аннотация:Approximate number sense (ANS) is usually tested by blue-yellow dot test in which participants have to compare two sets of dots and to select larger set. Numerous studies have demonstrated that visual properties of sets such as surface area or convex hull have the effect on numerical judgment. It is unclear which characteristics of two sets – numerical or visual properties – have a larger effect on numerical judgment. In this study we have estimated the effect of two visual properties (surface area and convex area) on numerical judgments in intermixed format of presentation of dots. To fulfill our goal we use longitudinal sample of schoolchildren and estimate the effect of visual properties on numerical judgment in blue-yellow dot test in first and fourth grades. The sample included 138 participants (46% girls) from one urban school. The mean age at first grade was 7.84 years (SD = .34, range 7.06–8.37) and 10.77 years at fourth grade (SD = .36, range 9.72–11.85).We estimate the effect of visual properties adjusted for numerical properties of sets using multilevel regression models where trials are nested in individuals. Our results have revealed that in intermixed format surface area has a larger effect than convex area. The effect of surface area increases from first to fourth grade. Additionally, we demonstrate that the effect of visual properties varies depending on size of sets.