Environmental Engineering Reference
In-Depth Information
Fig. 2. Visual conditions. A) No vision-NV B) Vision to movement onset-VMO C) Vision to
peak velocity - VPV D) Full vision crude-FVC E) Full vision-FV.
Results - Transport Component:
Movement time results for young adults showed that crude
feedback of the hand (both FVC and VPV) resulted in performance that was not different
from performance under natural viewing conditions (FV) (Figure 3B). Conditions where this
feedback was provided only to movement onset or not at all (VMO and NV) showed distinct
performance deterioration. This pattern of results has been replicated several times in our
lab (Mason, 2007; Mason & Bernardin, 2008; Mason & Bernardin, 2009). Older adults did not
show any differences between visual conditions, indicating that they used a transport
strategy that was independent of visual feedback of self (Figure 3D). While this strategy was
effective for performance of the current experimental task, it could result in significant
limitations with more complex and continuous tasks. For middle age adults and children
(Figure 3C and 3A respectively), results indicated that they make use of full visual feedback
of their moving limb to improve performance, but use of any crude feedback failed to
provide significant performance enhancements.
The peak velocity of the transport varied with visual condition for all age groups, but
children showed the most distinct effect (Figure 4). All conditions with altered feedback
(FVC, VPV, VMO, and NV) had significantly lower peak velocities when compared to the
natural viewing conditions (FV). Peak-velocity is determined by feed-forward motor
planning mechanisms. Therefore, since slower movements are more accurate, it appears that
children used a pre-planned strategy of slowing their reach to enhance the accuracy of their
transport when they were only provided with crude visual feedback or no visual feedback.
Finally the results from the limb deceleration data, which give an indication of the portion of
movement allotted for closed-loop sensory feedback processing, shed light on the same
phenomenon mentioned previously in older adults: this age group did not alter their
movement patterns based on the visual feedback conditions provided. This finding is
