When you can’t make things visible, you can give feedback via sound. Ableton Live is easier to use because everything on the screen is functional. Propellerheads Reason is an annoying program because its skeuomorphic design puts as many decorative elements on the screen as functional ones.
Feedback is an important way to help us distinguish the functional parts from the decorative ones. Helpful designs use visibility (making the relevant parts visible) and feedback (giving actions an immediate and obvious effect.) Everyone hates the power buttons on iMacs because they’re hidden on the back, flush with the case. Distinguishing the switches by shape, size, or grouping might not look as elegant, but would make it easier to remember which one does what thing. Norman gives examples of how much designers love rows of identical switches which give no clues as to their function. The absence of constraints makes things confusing. The arrangement of knobs controlling your stove burners should match the arrangement of the burners themselves.
Google Glass was an epic failure because its early adopters ran into the cultural constraint of people not liking to be photographed without consent. (Not sure how these are different from semantic constraints.) Somehow we all know without being told that we’re supposed to face forward in the elevator. We have a slow cooker that uses lights in the opposite way and it screws me up every time. We know that red lights mean stop and green lights mean go, so we infer that a red light means a device is off or inoperative, and a green light means it’s on or ready to function. Door keys can only be inserted into keyholes vertically, but you can still insert the key upside down. Affordances suggest the range of possibilities, and constraints limit the alternatives. We use affordances and constraints to learn how things work. The best-designed things include the instructions for their own use, like video games whose first level act as tutorials, or doors with handles that communicate how you should operate them by their shape and placement. But as the possibilities multiply, so do the challenges. We can deal with new things using information from our prior experiences, or by being instructed. User experience design is easy in situations where there’s only one thing that the user can possibly do. Note-taking for User Experience Design with June Ahnĭon Norman discusses affordances and constraints in The Design of Everyday Things, Chapter Four: Knowing What To Do.