Models and Theories in Human-Computer Interaction/The investigation based on a single theory (Fitts' Law) might not help for the success.

My previous discussion regarding the limitation of Fitts’ law on mobile device introduced an attempt to solve the motion-behavioral problem, a finger gesture-based keyboard design. The solution is named “8pen”, illustrating that the most natural finger gesture on a touch panel is circling, and drawing continuous “8”s on the screen. I previously mentioned 8pen in a positive manner, an alternative suggesting an innovative way to type letters with ease. However, at this point, I’d like to see this application with other theories, GOMS, TAM and Diffusion theory, and discuss its limitation.

With a lens of Fitts’s law, 8pen seems innovative, providing physical ease of use within the comfortable reach of fingers. It gained big applause  when it launched on the market several years ago. However, the innovative handwriting tool has failed to be a "dominant design" (Schilling, 2005), because the QWERTY keypad still dominates the mobile keypad. The reason can be explained by GOMS models. The Goal, typing a message will be the same. On the other hand, the following three elements, Operator, Method and Selection are all newly created. Instead of key stock operation, it suggests circling gesture; none of the Methods is previously mastered with cognitive skills; thus, Selection becomes ambiguous. The lack of skilled behavior (Carroll, 2003) makes laymen complex. As advertised in the video, the new method might provide psychological comfort -“perceived usefulness and ease of use”(Davis, 1989) to try the new interface. But the complexity of behavior from the new interface (environment) discourages the user to try relentless problem solving to build skilled behavior. (Carroll, 2003)

At the end, the tool has failed to jump into the safety zone of Early Adopters from innovators and stays in the first category of Roger’s innovation (Rogers, 2010).

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