In an episode of Friends, Monica becomes obsessed with a light switch that, according to Joey, does “nothing.” Monica, convinced that it must control something in the apartment (“They wouldn’t have put it there if it didn’t do something!”), begins an obsessive hunt to uncover what the switch does. Though it’s scarcely more than a silly subplot, Monica’s dilemma exposes an interesting household problem: Every home seems to have a mysterious light switch somewhere—near the back door, next to the porch light, at the basement stairs, along a row in the den. A light switch that does nothing.
The light switch is a lovely, ordinary thing. You can look at one and understand intuitively that the up position means on and the down position means off. The panel sits flush against the wall, elegant in its unobtrusiveness. The placement of light switches is so familiar that in the dark, you can feel around at the standard height (four feet from the ground) until you find the right panel to illuminate an unfamiliar bathroom.
Light switches exemplify familiar design, which, according to Henry Petroski’s Small Things Considered: Why There Is No Perfect Design, is a name for things that are “so predictable in their form and function that we do not give them a second thought.” We haven’t given light switches much thought for nearly a century now. The toggle light switch was patented in 1917, replacing the push-button switch of the late 19th century. Since the toggle’s inception, it has remained the most ubiquitous switch in North America. The 1980s saw the introduction of the rocker, a flat-paneled switch that became popular domestically and throughout Europe and Asia. But the rocker was really just a facelift, a minor aesthetic evolution of the traditional design similar to the shift from push-button to toggle. The light switch has essentially never changed.
In that episode of Friends, Monica was confronting a problem inherent to light switches: mapping. A switch does not designate what light or outlet it actuates or if it even controls a circuit at all. According to human-centered design, a pervasive design philosophy in user experience engineering, this amounts to a total failure of task analysis—when a function does not communicate to the user what it does.
Think about the times you've gone to an unfamiliar home and had to guess which toggle turned on which light. You try one and it turns on the porch light. Another and you've activated the garbage disposal. There's a big design question here: Has the light switch's mapping problem not been solved because no one has come up with a better solution in the past century, or because we’ve accepted its design as satisfactory?
According to Don Norman, co-founder of the Nielsen Norman Group, it’s the latter. Norman, a cognitive scientist, is an influential advocate of human-centered design and the author of the user-interface (UI) textbook The Psychology of Everyday Things. Despite being published in 1988, it remains a seminal text for UI design programs (a friend of mine in the master’s program at the University of Washington’s Human Centered Design & Engineering department affection refers to the book by a nickname, POET.) By definition, human-centered design is focused on the needs of the users rather than secondary concerns, like aesthetics. This design philosophy pervades much of modern user interfaces.
In POET, Norman outlines his concerns in regards to his own home:
With six light switches mounted in a one-dimensional array, vertically on the wall, there is no way they can map naturally to the two-dimensional, horizontal placement of the lights in the ceiling. Why place the switches flat against the wall? Why not redo things? Why not place the switches horizontally, in exact analogy to the things being controlled, with a two-dimensional layout so that the switches can be placed on a floor plan of the building in exact correspondence to the areas that they control?
These aren’t rhetorical questions. Norman actually prototypes his idea of the solution, a panel protruding from the wall with a blueprint of the room and little switches in exactly the locations where the lights are.
Almost 25 years after he proposed it, Norman’s solution never took off. In his attempt to alleviate the mapping problem, Norman’s light switch unraveled all of the things that worked well about the original design. It was no longer intuitive, requiring the user to interpret a map with corresponding switches and breaking a century-long familiarity with the existing design. And not only was Norman’s switch obtrusive, but it was also ugly. Nevertheless, Norman’s concept was the only proposed home light switch solution I could find in the past century.
In Small Things Considered, Petroski argues that design always amounts to a decision-making process with clear trade-offs. As an example, Petroski discusses two-way light switches, which introduce a problem different from the mapping issue that bothered Norman: When two switches control the same light, up may no longer mean on and down may no longer mean off, depending on which switch was last used. The two-way relationship breaks the simplest physical affordance of the light switch. But Petroski argues that this isn’t necessarily a bad thing, raising the example of the two-way switch at the top and bottom of a staircase in his home. “This can be disorienting,” he writes, “but who would not gladly accept a moment’s confusion if it means being able to turn the staircase light on without having to go downstairs in the dark?”