In the first chapter of his book, "Designing Gestural Interfaces" and in his "Tap is the New Click" presentation at Stanford, Dan Saffer outlined the conventions for gesture interfaces. He warns designers to use gesture interfaces in appropriate environments and to create a safe space for users. If the desired action requires delicate manipulation then the use of more traditional tools might be appropriate, but if the desired action is more commonplace then gestural interfaces should be intuitive and approachable. People don't want to appear ridiculous waving their hands around in public trying to get something to work, so gestural interfaces have been introduced in more private places like restrooms and the home.
Saffer also discusses how the type of interaction and the type of sensor available have an impact on each other. Sensors can judge, light, pressure, proximity, acoustics, tilt, orientation and motion and the type of action a user takes must of course match those sensors.
Saffer says that good gestural interfaces have some common characteristics, such as being discoverable meaning not so hidden a novice user can't operate it. It should also be trustworthy and attractive. The system should be responsive and provide feedback. It should be appropriate for the culture, situation etc. It should also be meaningful, smart, clever, playful, pleasurable and good.
The author mentions the importance of physical considerations, such as the fact that for touch screens, the hand will block any information that is below a touch point, so interfaces should be designed with this in mind.
Gesture interfaces take a lot from traditional interfaces, but designers must consider additional factors when creating them.
My Thoughts
One point that Saffer makes is that people don't want to feel like idiots and might feel more comfortable using gestural interfaces in the home or more private spaces. Another consideration for using gestural interface in more private spaces is that it prevents accidental triggers. When people are alone they don't tend to gesture as much as when they are out communicating with other people. So an accidental trigger is less likely.
Saffer touches on the idea that the type of sensor is important for the type of interaction. This is VERY important for designers and engineers to communicate on. Recently, when designing a robotics exhibit to teach the idea of programming to children, I experienced a miscommunication where the physical robots did not have the attributes that they were assumed to have. We referred to the robots as "hearing" things when there were no acoustic sensors, it was actually wireless transmission of signals taking place. This caused real confusion when the action of the robots did not perfectly match what people were seeing take place given the script and expectations. I think engineers will work at things and create a desired action, without explaining the more technical details, but when a project gets modified based on certain assumptions, that is when work arounds can cause problems and the importance of matching sensors to actions comes in.
In discussing nuanced gestural interface, the "smile detectors" on some new digital cameras comes to mind. Gestural interfaces could be created based on mood detection and emotional responses. If you're in a good mood, peppy music could automatically play etc.
In his talk, Saffer mentions how fake nails can be awful for touch screens. I wonder if we'll ever get to the point where fake nails are created to be used as a stylus and purposely created and worn for computer interface work.
In this gesture interface situation in a museum I have seen first hand what Saffer is talking about when he says functions like hovering are not good for gestural interface. In this dance motion capture exhibit, people are asked to manipulate a cursor (another thing saffer says to avoid) over a "next" button and hold it there. Visitors have a difficult time doing this and it is not instinctual to hold their hand still in a point in space. They often need assistance with this. It might have been better to design a specific action sequence for the "next" function. Any other ideas on a better option? Perhaps a clear swipe of the arm from side to side?
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