Twenty-one children with Down syndrome (DS) and 20 without disability, ages 3 to 11 years, completed the experiment in which they were asked to grasp and lift cardboard cubes of different sizes (2.2 to 16.2 cm in width). Three conditions were used: (a) increasing the size from the smallest to the largest cube, (b) decreasing the size from the largest to the smallest, and (c) a random order of sizes. Children with DS were found to have smaller hand sizes in comparison to age-matched children without DS. In addition, the shift from one-handed to two-handed grasping appeared at a smaller cube size for children with DS than for children without DS. However, when the dimensionless ratio between object size and hand size was considered, the differences between groups disappeared, indicating that the differences in grasping patterns between children with and without DS can be attributed to differences in body size.
Cortical idiosyncrasies predict the perception of object size
