# Hand Gestures in Virtual and Augmented 3D Environments for Down Syndrome Users
## 5 Discussion  
### Usability Issues and Design Considerations  
People with DS usually encounter problems with the fine motor skills required to interact with gestural interfaces. From our experiences and studies exploring 2D gestures on touchscreens that have involved individuals with DS [11] we can confirm that some 3D gestures (Mid-Air) prove easier and straightforward for users with DS to perform than the 2D gestures used on touch screens. This should be taken into account when designing interfaces otherwise user performance will diminish. The easiest gestures for users with DS to perform in AR y VR environments are Stop and Point out. Overall, the Swipe gesture was the hardest to perform. [PERSON] [23] reported the Tap gesture as being one of the easiest gestures to perform with touch interfaces; however, in this study the Tap gesture proved to be one of the hardest to perform when using Atheer and Leap Motion in an AR. Having a better understanding of the difficulties encountered by individuals with DS is the first step towards explaining and addressing any problems that arise that arise with these technologies. In reviewing the results obtained for hypotheses H1A and H1B that are detailed in Tables 4 and 5, no statistical significance differences have been identified between either of the study groups for the successful execution of the gestures Stop, Take, Point and Swipe, nor the execution time of the gestures Grab and drop, Take and Swipe. Based on these findings, it appears that when it comes to the design of virtual reality or augmented reality applications the aforementioned gestures prove to be those best suited for all users. Our recommendation would be to give priority to gestures that provide the greatest guarantee of success; therefore, we would argue that these findings form part of basic guidelines for developing apps and should be taken into account when establishing the functions required during a task (precision or speed of execution). When selecting gestures there will be pros and cons involved in selecting one over another. For example: Stop, Take or Point may take longer to complete, but there is a higher guarantee of success for all users; Grab and drop and Take completion times are the same time for all users, but nonetheless these gestures prove more difficult for all users to consistently perform correctly; and the Swipe gesture (move with two fingers) is the gesture par excellence as it can be correctly performed by all users. In this study, the authors have found that any usability testing for gestures must be conducted for each environment independently. Below is a list of recommendations that serve as design guidelines for apps that require Mid-Air gestures:  
* Basic recommendations regarding cognitive psychology are very useful, as are those proposed by [PERSON] [23]. * For 3D gestures, try to use gestures that involve the whole hand and avoid gestures that require the use of fingers and precise movements. * Regardless of environment, whether it be virtual reality or augmented reality, it is advisable to design apps so that they use gestures similar to those used in real life since the goal is to simulate within an synthetic environment those actions that are performed in the physical setting. * Ensure devices have a greater margin of error for gesture recognition. * Avoid the use of objectives to touch that are too small. * Do not assume that gestures for a touch interface should be similar to those in a 3D environment or headset. * When design with 3D gestures, give preference to: stop, point, pan and grab. * Gestures that are much harder to perform can be used to confirm critical tasks, such as deleting data. For critical tasks, such as Delete, use an appropriate gesture for the action that is being performed and a second gesture to confirm the action. * Avoid gestures using two fingers.