Typical development of Motion perception and Form discrimination abilities in children

Visual functions have been widely investigated in patients with developmental disorders. This study aims to analyze the development of dorsal and ventral visual function in children with typical development, measured as motion and form discrimination abilities. A sample of 304 children (age: 4-12 years; 154 males) participated in the experiment. Non-verbal intelligence (Raven’s matrices), visual acuity (Lea test), motion perception (motion coherence test-MCT) and form recognition (form coherence test-FCT) were assessed. The MCT consists of 150 white dots on a black background moving coherently at a constant velocity in one of the eight directions (signal) or in a Brownian manner (noise). The task was to recognize the direction of the signal dots. The FCT consists of white dots (signal) composing one of eight possible forms through spatial alignment of the dots, the noise was created by non-aligned dots distorting the form. The task was to recognize the form. Difficulty was increased by reducing the dot coherence (signal/noise) from 100% (no noise) to 36% in five levels. MANOVA showed a significant increment of motion and form perception accuracy with age, steeper for form as compared to motion recognition. Both functions are influenced by noise but motion discrimination seemed to be less affected. While noise had a stronger effect on the younger children in the FCT (worse performance with noise in the youngest) no such age effect was found in MCT. Motion and form perception are related to general intelligence at different ages as well as to the visual acuity. These results confirm the slowness in development of dorsal function as compared to ventral function. Visuo-spatial attention, general intelligence and visual acuity mediate the visual functionality development.