Ever since those first, uncertain steps we took as a child, we have all held an intuitive sense of the basic laws of physics, if only for survival's sake. When a pencil rolls to the edge of a desk, we listen for it to hit the ground and are surprised if it doesn't. If you throw a rubber ball, it will bounce. If you toss an egg, it most likely won't. Parents don't teach their children these things, they are learned by rote.
Though you may not have realized it at the time, from your earliest moments spent cruising around the living room as a toddler, you were already absorbing a great amount of intuitive knowledge about your environment. Some of it was learned through pain (avoid the sharp corners of the coffee table!) and some through pleasure (that warm blankie sure is nice!), but all of it was useful.
This principle is called "implicit memory" and is defined as "a type of memory in which previous experiences aid in the performance of a task without conscious awareness of these previous experiences." (Wikipedia)
All humans bear within them a vast amount of such knowledge—innumerable bits of unspoken information they've accumulated through millions of tiny acts of trial and error, decisions and consequences. Once assimilated, this subconscious programming smoothes out the rough edges of our worldview, making our complex environment much less overwhelming than it otherwise would be. When we feel safe and know where we are and what is likely to happen around us, our brain can focus all of its efforts into perceiving and processing more important or novel information. If we had to consciously think about every insignificant sensory input, even the most peaceful environment would quickly overload our senses.
Because their users aren't blank slates, UX designers (whether they realize it or not) leverage implicit memory in every single application they create. It is up to them, therefore, to make this vast reservoir of expectations and skills work in their favor.
Experience Builds Expectation, Expectation Builds Comfort
When applied to a task, implicit memory is more precisely called "procedural memory." Much as how muscle memory allows athletes to perform complex maneuvers without conscious thought, this acquired ease comes into play when we set out to complete recurring tasks such as tying our shoes, opening a door, or interacting with software interfaces.
After spending even only a short time using a computer, keyboard and mouse, we learn to recognize and interact with common UI conventions. This permits us to concentrate on the task at hand and not every single detail of the specific software tool we're using. Our subconscious becomes quickly accustomed to repeated UI constructs, the mouse feels less artificial (if we even notice it at all), and eventually our mind only calls out for conscious help when a meaningful decision needs to be made.
This human trait allows people of wildly varied backgrounds and occupations to become extremely comfortable and productive using computers. Navigating and interacting within an artificial environment of software interfaces can (and should) feel as natural as navigating the furniture in our parents' living room. When our ready store of procedural memory meets with proper experience design, we can trust implicitly in our ability to accomplish whatever we set out to do.
Conversely, whenever a piece of software behaves erratically or breaks the unspoken rules on which we've come to rely, it can be jarring and, by forcing us to consciously question our expectations, requires more conscious thought on our part. This can be catastrophic for a user experience, much like how forgetting to walk might feel; once user confidence is shattered, every decision made must be a conscious one. This is taxing and alienating to users who were, but moments before, wholly secure in their abilities.
How can we avoid this? By leveraging shared user experiences and by priming our users for new or unique experiences.
Much Ado about Priming
Priming is the process of establishing implicit knowledge through an initial stimulus. This "teaching moment" is what sets the subconscious template for future use.
When you were learning to walk, you likely only had to fall against a piece of furniture once or twice before learning to avoid it. Though the specific events that taught you to avoid knocking into grandma's evil mahogany end table are long lost in the fog of time, that primed learning still kicks in every time you need to negotiate shin-threatening furniture in a cramped living room. Somewhere inside you, an inner toddler cringes at the thought of one more accidental furniture collision.
This process of learning through experience is known as "priming" and it is the key to shaping procedural memory.
Repetition on a Theme
Whether you're talking about pop, classical, or hip-hop music, repetition allows us to feel familiar with a song, even when we're hearing it for the first time. When a tune gets stuck in your head, it's usually the chorus and not the bridge that's gumming up your brain. That's because if you are trying to get inside of someone's head, repetition is the tool of choice. This same repetition is the key to effective priming.
Thankfully, when it comes to user interfaces, much of the required priming has already been done for us. Most likely, by the time they get to your software, your users will have been using computers for some time and will have built up a certain level of comfort with the standard UI controls such as buttons, sliders, and toggles. For this reason, whenever reasonable, we should leverage existing UX conventions when designing our applications. Some simple rules of thumb apply.
First, however you may choose to style your application, make sure that users can recognize standard controls such as buttons or toggles. This includes keeping users from confusing one UI element type with another (mistaking a label for a button, for instance). This is crucial because if a user has to think about what a control is, you've lost the advantage of leveraging implicit memory relating to that control.
Second, make sure that these controls behave according to established convention. If you want to break convention, you must make sure that your control looks quite different from its standard counterpart. If you fail to do so, by the time a user discovers the difference, you will have already confused him, throwing a fog of doubt over your whole interface. By breaking the trust your users have in your UI and in their own ability to navigate it, you sabotage your experience, however carefully crafted it may be.
So, when you're creating a new user experience, think pop music, not free-form jazz. You want your users to be able to predict what you're going to do next, or at least avoid jarring them out of their comfort zone with a sudden harsh or dissonant note. There is room for creativity, not alienation.
Release Their Inner Toddler
When users experience software for the very first time, they are much like toddlers: fearless yet uncertain, inquisitive yet ready to spring to action. If we want new users to move quickly from toddling to full cruising speed, we must prime them quickly and maintain a consistent experience that reinforces that initial learning.
As mentioned above, the best way to teach a new interaction is through repetition. Introduce new concepts to your users early and reuse them often. For instance, if you allow your users to drill down into data controls to see their contents in more detail, reuse the icon or button for any other such increases in the level of detail. Reuse the same metaphor for both drilling in and out of data (in this example, we're using a magnifying glass).
Drill in for more detail
Drill out for less detail
Similarly, if you provide your users with more than one search capability (e.g., search for users and for cities), reuse the same icon for the various searches and present results in the same or at least a similar format. That way, once they've used one of your searches, they'll already know how to use any of the others.
|Two searches, one icon|
These are simple examples and may well seem self-evident but the concept applies to (and is most powerful for) specialized and therefore less common interactions where the icon or metaphor used might not be so obvious. The key is that consistent repetition makes even strange things familiar.
While it is easy to imagine how priming through repetitious and consistent user interactions can lead to familiarity with a user experience, UX designers might tend to overlook an even richer source of pre-primed intuitive memory: the real world.
In this modern age, many citizens of the developed world "live" in software at least a part of every day, however all humans live full-time in the real world. By tapping into the bank of natural implicit memories, we can move our artificial experiences into a level of intuitive comfort rarely seen in software. To do so, we must model parts of our experiences off of the world around us. One common way is to use UI metaphors based on real objects or concepts but another is to actually build physics into interfaces.
The analog interfaces of yesteryear provided intuitive feedback to users. Whether it was the comforting resistance of a volume knob as you turned it or the click of an on/off switch, when we interacted with our home stereo we knew that our input was being received. We could easily tell the upper and lower limits of the allowed input or, through the clever use of clicks, the key positions of the controls. For instance, the sliders of a graphic equalizer or a fader control often provided tactile feedback when you are at the dead center of their range of motion.
When designing what are in effect purely imaginary controls in software, we should try to include these same kinds of implicit signals. In fact, using modern mobile devices, it is often possible to provide haptic feedback to certain user actions. Simulated physics through the use of tweened animations can also be particularly useful, when animating state transitions for instance. Among other things, this purposeful use of motion can give weight and context to the navigation between screens.
Imitating the real world comes with risks, however. Because people have a natural sense of what is authentic, it is important to avoid ever presenting them with physical impossibilities or paradoxes. For instance: if you use an animation to transition from one screen to another, when reversing the navigation you should also reverse the animation. (i.e., If you slide the screen left while navigating one way, you must slide it right when going the other.) Inauthentic physics feels closer to a parody than imitation. The last thing you want is for your application to behave like a Looney Tunes cartoon where characters run off one side of the screen and back in the other.
Driving it Home
As we have seen, users come into any experience carrying a wealth of implicit and procedural memories. Some have been gained through their everyday, real, lives while others come from their time using other software. It is up to the skilled user experience designer to employ their abilities and foresight to create nuanced applications that leverage that very human intuition while priming up a new set of memories. When paired with skillfully designed interfaces, these nearly accidental skills can transform even the most novice users into intuitive experts.