Interference in geometry among people who are blind

Background: Geometry, a central branch of mathematics, is challenging for schoolchildren. Studies have shown that, when comparing perimeters of geometrical shapes, many sighted participants experience interference from the area variable, possibly stemming from the visual differences between the geometrical shapes. Accordingly, we hypothesized that such interference would not be observed in participants who are blind, who use the tactile modality to detect the properties of shapes. Methods: Thirty participants, 15 who are blind and 15 with sight, explored pairs of geometrical shapes tactilely or visually, respectively, and compared areas and perimeters. Results and conclusions: Surprisingly, accuracy and response time findings suggested that the two groups had a similar pattern of performance, and hence that area also interferes in comparison of perimeters among people who are blind.