The Impact of Body-Scaled Information on Grasping Action in Toddlers with and without Down Syndrome

Background and purpose: Studies of adults and typically developing (TD) children find the number of hands and fingers used to grasp an object is influenced by the relationship between object size and hand size. Children with Down syndrome (DS) between 3 and 11 years have shown no differences in number of hands (1 or 2 hands) used to grasp different sized objects compared to TD children when the object size was body-scaled. The purpose of this study was to examine whether body-scaled information affected the number of hands and fingers used to grasp different sized objects in toddlers with and without DS. Method: Ten toddlers were included, 5 DS ( = 16 mo) and 5 age-matched TD ( = 16.3 mo). Subjects were videotaped grasping 14 boxes, 1.4 cm to 13.5 cm. in size. Number of hands and fingers used for grasping were recorded. Descriptive statistics, t-tests and Spearman correlation coefficient were used to compare the differences between toddlers with DS and TD. Results: Toddlers with DS had significantly smaller hand length than toddlers without DS (p=.004 right hand, p=.007 left hand). As box size increased, both groups switched from one-hand to two-hand grasping. There was a significant difference between groups where this transition occurred (p=.02). However, when the body-scaled ratio between object size and hand size was considered, the differences between groups disappeared (t(8)=1.479; p=.18). Moreover, the number of fingers used to grasp boxes also increased with increasing box size across both groups (ρ=0.94). Conclusion: Toddlers with DS show similar body-scaled grasping pattern as their age-matched peers with TD indicating that the differences in grasping patterns between toddlers with and without DS may be attributed to differences in body size, besides the motor abilities.