I was on board with Fishkin’s embodiment and metaphor axes in trying to categorize TUIs by using the two spectrums. But when I came across the example of a greeting card as a TUI, I felt a certain lacking in their model. Since TUIs are by definition meant to be handled physically by humans, wouldn’t it make sense to somehow include human perception into their model? I am suggesting a third spectrum which measures how aware humans are that the TUI they are using employs some form of computation to produce the output. This is somewhat a measure of the effect the embodiment and metaphor produces in the users.

I have never given any thought to audio greeting cards. The written message being like an audio messages…I never connected the dots there. It’s just a pleasant singing card to me. On the other hand, I am very aware of how programmed the clay sculpting mechanism is. By creating the third spectrum, we can assess how well or poorly the TUI has managed to blend into our lives, whether we are fooled into thinking it’s like a mechanical door knob or can plainly see that between our input and output lies a world of code.