McCullough’s argument that “the computer is inherently a tool for the mind and not for the hands” resonates deeply with me and I have been reminded of it while encountering several UIs. Musical instrument apps and drawing apps are a few examples that come to mind immediately.
Upon trying to play music on a guitar app vs. the real guitar and keyboard app vs. real keyboard, I have experienced first hand that hands are differentiated and very closely connected to the mind. The mind and hand perceive guitar strings very differently from the screen interaction with the guitar app. Similarly, the mind and hand have a very different experience when a keyboard key is pressed on a real keyboard vs. on the app. As McCullough says, “ The knowledge is not only physical, but also experiential.”
A gutarist will tell you how losing a fingernail will make a difference, why they obsess so much over adjusting the strings till it is just right and they probably won’t be able to explain very well why a given pick is their favourite for outdoor performance and why another pick is their favourite for an indoor performance. It exemplifies McCullogh’s argument that “ The way of hands is personal, contextual, indescribable.” While the string adjustment is scientifically explainable, the fact that a particular pick feels just right to their hand is personal, contextual and very hard to explain or like McCullogh says ‘indescribable’.
A very similar argument is applicable to apps used for drawing. While they come very close in emulating strokes from different angles and pressure levels, the experience is very different from drawing on canvas. While the digital canvas can emulate the look of various canvas textures, the hand cannot feel the differences as it rests against the touch screen. Also, the drawing instrument (pen/pencil/brush etc) cannot experience the friction of different surfaces and the effect such differences are digitally created which is experientially quite different from how things work in the physical realm.