# The Effects of Augmented Reality Interaction Techniques on Egocentric Distance Estimation Accuracy
## 4 Discussion
Using a technique similar to the direct pointing technique used in this study, [PERSON], [PERSON], and [PERSON] [13], who utilized direct matching and reaching for depth judgments, also observed a slightly overestimated judgment of 0.5 to 1.9 cm over reaching distances of up to 50 cm in a mixed environment of VR and real targets displayed by an nVisor ST60 head-mounted display (HMD) that allowed a 60\({}^{\circ}\) diagonal field of view (FOV). Likewise, using a widescreen display system and a triangulated pointing task, [PERSON], [PERSON], [PERSON], and [PERSON] [67] found that overestimations of up to 50% occurred when a target was projected at a distance of 1 m from the observer. In a recent study by [PERSON] and [PERSON] [11], vision-based and memory-based pointing methods were used to estimate the egocentric distances of 3D stereoscopic and real targets. Their results showed that egocentric distances were overestimated by 10 to 11 cm at distances of 100 cm and 150 cm in the stereoscopic environment, and their finding was consistent with their previous study [32]. Although earlier researchers based their conclusions on the response methods separately, their approaches can also be categorized as direct interaction methods. The overall estimations at the three tested egocentric distances showed underestimation with the indirect cursor technique and overestimation with the direct pointing technique. This contrast could be attributed to the difference in the methods of distance judgment, which has been interpreted as two representations of visual space with respect to the utilization of interaction techniques [68; 69], namely, a cognitive/perception representation for the indirect cursor technique and a sensorimotor representation for the direct pointing technique. The activities in direct pointing involve vision-for-action of direct reaching to a reference target, in which the participant's attention (perception) is focused on the target to be selected and the hand is moved closer to the goal through a motor (action) control. On the other hand, the indirect cursor technique involves only vision-for-perception or matching of a target object (i.e., virtual cursor) until it perceptually matches the reference target, with less or without any motor control (i.e., direct reaching to the target). These two different representations of visual space--a cognitive representation driving perception and a sensorimotor representation leading to action--could have influenced the estimation. At present, however, it is difficult to conclude that visual perception differs from participants' responses or actions with respect to direct and indirect interaction techniques, as only a few related comparative studies are available. Further study with a greater focus on this variable is needed to clarify its effect on egocentric distance estimations. This study provides important information on how interaction techniques (direct pointing and indirect cursor) affect the accuracy of egocentric distance estimation for interaction with objects displayed stereoscopically at different parallaxes. It is also evident from the present study that interaction with the direct pointing technique could mitigate the underestimation problems commonly reported in VE studies. In this experiment, we found that the accuracy of egocentric distance estimation with the direct pointing technique increased as the egocentric distance increased (as shown in Figure 4). This result was also supported by statistical evidence that egocentric distance estimation with the direct pointing technique was significantly more accurate (\(p<0.05\)) at the farthest distance of 150 cm than at the other distances of 90 cm and 120 cm. The result is consistent with previous studies [11; 35], which reported that the accuracy of stereoscopic target selection was lower for targets closer to the eyes.