With vision, the average X error was 1.5 mm and the average Y error was 1.2 mm, while without vision the X error increased to 11.6 mm and the Y error increased to 5.7 mm. Individual Differences Figures 3 and 4 demonstrate the individual differences in bias and consistency of object manipulation, in terms of standard deviation for the eight subjects. In general, individual differences were greater in bias than in consistency during object manipulation, Deprivation of visual feedback information of the hand and the wooden cube increased the performance variation among the individuals. Variable Error Figure 2. The magnitude of the human bias in object manipulation is larger in the no vision condition, but the trend of the bias is very consistent whether or not visual feedback of the hand and the cube are present.
Users tend to overshoot the target, but under-rotate the target orientation.
However, the change in consistency over different visual conditions is not as dramatic for object orientation as for object transportation. This implies that direct manipulation interfaces in virtual environments will be more effective should they utilize a calibration mechanism which accounts for individual biases. The error values presented in Figure 1 and 2 may serve as rule of thumb for determining the tolerance bounds for matching or selection tasks. Fikes, T.G. Spatial and temporal characteristics of feedforward reaching. The 36th Annual Meeting of the Psychonomic Society, Los Angeles CA, 1995.