The role of binocular vision in the performance of complex manipulation skills


Many activities of daily living ,including fine manipulation skills, rely on vision as a primary sensory input. The visual system has the capability of combining two slightly different inputs from each eye into one image which is perceived in depth. Research suggests that the advantage of having coordinated inputs both eyes is dependent on age and motor task. The aim of this research is to examine these two factors by comparing monocular and binocular viewing in the performance of two complex manipulation tasks in normally-developing school-aged children and healthy young adults. Participants tested in the study were visually-normal children (n=34; age 6-12) and adults (n=14; age 19-38). Participants’ fine motor skills were assessed under binocular and monocular viewing conditions using a peg board task with three levels of difficulty, and a bead threading task with two levels of difficulty. The main outcome measure was the total movement time (MT) to complete each task. Binocular ratio (binocular MT/monocular MT) was also calculated for each participant for both manipulation tasks to quantify the extent of binocular advantage. Results revealed that MT was significantly shorter during binocular compared to monocular viewing for the bead threading task (16%) but not the peg board task (5%). The mean binocular summation ratio showed that 9-12 year-old children had a greater binocular advantage in comparison to 6-8 years old children. Interestingly, the binocular ratio in 6-8 year-old children was closer to 1, indicating that MT during binocular and monocular viewing was similar in children at this age. These data suggest that younger children are still developing the ability to integrate binocular visual information during online control of movement. Based on these results, it can be concluded that the advantage of binocular vision for the performance of manipulation tasks is dependent on age and task complexity.