During World War II, over a period of two years, about 400 P-47 (fighters), B-17 and B-25 (bombers) planes suffered accidents after incomprehensibly retracting the landing gear while landing. Alphonse Chapanis, one of the pioneers of the discipline of Human Factors, immediately identified the problem: the controls for the landing gear and flaps were placed side by side as well as being shaped as identical levers. In a situation of high cognitive demand such as landing, even seasoned pilots with many flying hours in the cockpit confused both controls.
Chapanis proposed a solution that became a world standard in aviation after wartime, a shape coding that enabled to easily distinguish and identify controls function without looking at them, using only touch. The quick fix during the war consisted of gluing strips of rubber on the landing gear lever, giving it a grooved form, and shaping a wedge silhouette on the other control, reminiscent of the flap.
In early 2015 Ford calls for revision 13,500 Lincoln MKC because drivers accidentally turned off the engine while driving. It was not a minor issue, as several security systems may fail if the engine is not running.
The different positions of the automatic transmission of MKC are selected from a keypad on the left side of the center console. The start / stop button is placed under the “S” (sport) gear position, presenting a great continuity with the design of the other buttons, a unity that is only broken by a LED indicator and clear labeling Engine Start / Stop . In addition, this button was on the side of the infotainment touchscreen.
The quick fix was to place the Start / Stop at the top of the keypad. At least now is further from the touchscreen and, in case of confusion with position “P” (parking), less severe.
In the 40 Chapanis worked to introduce the discipline of human factors in the design of cockpits, how can we still find the same kind of problem detected 70 years ago?
First, beacuse of something very basic: a problem of proximity and similarity to other controls, as well as visual continuity with a serie of them.
But also because of wasting non-visual resources like shape, volume, texture, vibration resistance movement … (temperature and weight seems to be more difficult to implement here).
Haptics, the science of touch, deals with these resources, or rather the perception of these types of information.
Haptics combines information obtained from cutaneous receptors (tactile perception) and information of the movement and position of the joints (kinesthetic perception).
In many cases the sense of touch can be a tool for the design of the interface, both to give feedback and function recognition.
Often, the task to be performed trough a control is not the only ongoing, it could even be secondary. In these cases, even an explicit labeling (Engine Start / Stop) and a familiar position for the user may not be sufficient to avoid mistakes.
In other cases, also for multitasking or due to context of use, forcing the user to gaze at the control is an annoying interruption. Consider, for example, the volume control on headphones, sports devices, a camera, etc.
And sometimes the size limitations of the control itself complicate its handling.
But the “flat” trend came to physical interfaces long before we knew what it was on digital design. First the spread of capacitive switches, later touch screens, changed our expectations about the behavior of the controls. Where before we expected a recognizable surface and a feedback in the form of variable resistance, clearly indicating when the control is activated, we now seek a subtle touch with a visual feedback. And that vision of what the technologically advanced and “modern” control extends to mechanical controls, which are designed with continuous surfaces, integrated into the product, and with short travel.
Even automotive industry, surrender to controls over-digitalization sometimes. It happens despite car manufacturers have specialized departments focused on giving each button or physical control the right feeling with a specific force-travel curve and an suitable interface to their function (eg BMW).
Passive and active systems
But interfaces using haptic controls that have attributes such as shape, texture, vibration and resistance to movement are not something from the past, and this is true for both passive and active systems:
- Passive systems: haptic properties of physical objects, mechanical, inertia, friction. It deals with the tangible interaction that can be found on a keyboard, a mouse or a knob.
- Active systems: the haptic feedback is generated by the device itself, based on actuators and software. This haptic interaction usually involves vibration.
The classic materiality of controls has not only not found a better digital alternative in some cases (eg smartphone volume controls, mute button, …), but has all the attention on some products.
There are devices where the body itself becomes a control, as the Nest thermostat, the Polar CS500 heart rate monitor or some products from Bang & Olufsen. There are also physical controls that integrate with digital interfaces to find the best of each.
Vibration has evolved from a “binary” use to more sophisticated implementations.
For example, we can use vibration patterns, playing with frequency and amplitude to encode messages far beyond a yes / no warning. The number of patterns (also called haptic icons, tactons or hapticons) we are able to differentiate is striking.
The use of vibration as a means to simulate mechanical feedback, has become popular with the Apple Force Touch trackpad. Also without mechanical parts, the Kindle Voyage provides a subtle feedback on thumbs that warn us we are turning the page.
Vibration localized in specific points on a touch screen seems to be around the corner. And maybe the next step is electrostatic screens with vibration that allows us to perceive countless textures and resistance to movement.
As more and more interactive products are not just a glass rectangle, attributes such as shape, volume, texture, vibration, resistance to motion, temperature and weight re-gain importance, so it never hurts to return to the “old” principles of haptics.