If nothing else, Norman's book, The Design of Everyday Things, will make you walk around looking at all the things around you in ways that you have never done before. His book discusses a lot of design philosophies on common objects that we encounter everyday. Although we may think that something is very simple in itself, Norman will tell you how much thought the designers have put into it and how much they have not.
One of Norman's questions is why some of the things that we use everyday are so complicated for us to figure out how to use them. He states that well-designed objects are the ones easy to interpret and understand; they contain visible clues, the correct ones, to their operations.
When the users walk up to a device, a conceptual model is formed in regards to what the device can do and how it carries out its functionalities. Norman points out that many of our everyday understandings are classified as "naive" or "folk" understandings, which often does not quite match the designer's idea for implementing the device. For example, the thermostat. You may think that if you want to heat up your home quickly, you would turn the setting all the way up for maximum heating. But the way it really works is that the thermostat is merely an on-off switch. It turns the heater on at full power until the temperature setting on the thermostat is reached. You cannot heat up your home any faster or slower.
From our mental model, we form our actions. An understanding of how we perceive our actions is very important for understanding the interaction between us and an everyday object. Norman puts forth a model known as the seven stages of action to describe the interaction.
The action cycle consists of three major components: goals, execution, and evaluation. A goal is what we want to happen (something to be achieved). Execution is what we do to the world. Evaluation is when we compare what happened with what we wanted to happen.
The seven stages are as follows:
Below is the graphical representation of the model.
When a user has a hard time using a particular product, this model can help in explaining what has gone wrong during the interaction. The difficulty lies in deriving the relationships between the mental intentions and interpretations and the physical actions and states. There are, what Norman calls, gulfs that separate mental states from physical ones.
The Gulf of Execution refers to the difference between the intentions and the allowable actions. The other, Gulf of Evaluation, refers to the difficulty in interpreting the physical state of the system and in determining how well the expectations and intentions have been met.
The seven-stage structure can serve as a design aid for designers to bridge the gulfs, providing a basic checklist of questions.
How easily can one:
In turn, Norman suggests the principles of good design:
Human memory can be distinguished into two different classes, short-term memory and long-term memory. Short-term memory is the memory of the just present. Information is retained in it automatically and retrieved without effort. But the amount of information that can be retained in short-term memory is very limited (plus and minus 5 chunks of information). Long-term memory, on the other hand, is the memory for the past. It takes time to put stuff away and effort to get it out again in long-term memory.
Because of our memory capabilities are limited, visibility acts as a good reminder of what can be done with a device. A good reminding method is to put the burden on the thing itself. Designers should give as much succinct clues to the users as possible on the device itself, without overwhelming or confusing the users. This supports the phenomenon of recognition over recall. Our ability to recall information is inferior to our ability to recognize it from some visual cue. Therefore, if there exists a good relationship between the coding or placement of the control and what it does, it makes the appropriate task easy to find. In turn, there will be very little to remember on how to operate the control and its corresponding effects, maximizing the use of the knowledge in the world and minimizing the use of the knowledge in the head.
A good conceptual model allows the users to predict the effects of their actions. This all depends on whether the designer's conceptual model (design model) and the user's mental model match or not. A design is successful if the users carry out the exact actions that the designer has in mind when designing.
In trying to match the conceptual models, Norman discusses the important concept of natural mapping. Mapping refers to the relationship between the controls and their movements and the incurred results. Natural mapping is the idea of taking advantage of the physical analogies and standards and with that, leads to immediate understanding of how something works. For example, when you want to move an object up, your tendency is to move the corresponding control upward.
Norman also points out the importance of feedback, the concept of sending back to the user information about what action has actually been done and its results. One excellent example of good use of feedback is the tone you hear whenever you press a button on a touch-tone telephone. The tone tells you that a button has been pressed and even tells you which one, since the tone varies depending on what number you press. Feedback of course is not limited to sound. There is also visual feedback, which Norman states that nothing succeeds like it. Good feedback can help the users interpret the effects of their actions and can guide the users through the future actions in the task sequence.
Simplifying the structure of the tasks that the users need to achieve their goals is also very helpful. There exists different types of structures: wide and deep, shallow, and narrow. Each of them has a representation of a decision tree. Wide and deep structures often refer to more complex activities such as playing chess. At each point where a decision needs to be made, there are many alternatives. In shallow structures, there are many alternatives to a decision; however, there are very few decisions to make after the top-level choice. As for narrow and deep structures, there are only a small number of alternatives, but each possibility in turn leads to another small number of choices. Designing devices that helps simplify structures can reduce the mental load on the users.
Natural constraints of objects can lighten the burden on the designers in achieving the same design goal. Norman has talked about several of these constraints. First one being physical constraints, which limit possible operations. For example, a large peg cannot fit into a small hole. When physical constraints are easy to see and interpret, a set of actions is restricted before anything has been done and no training is necessary for the user to figure it out.
This brings up the concept of affordance, which refers to the perceived and actual properties of the object, primarily those fundamental properties that determine just how the object can possibly be used. An excellent example that Norman gives is the design of door handles. On most of the doors to building's stairwell today, a flat horizontal bar across the door where it is easily reachable affords no operations except pushing. Its size and position supports the affordance of grasping. No labels are needed to tell the user whether to push or pull; the design speaks for itself.
The second types of constraints are semantic constraints, which rely upon the meaning of the situation to control the set of possible actions. For example, when putting pieces of Lego together, a rider on a motorcycle should be facing forward and no other ways in order for it to make any sense.
Then there are cultural constraints which are merely the cultural conventions that we have in our society. If designer follows this type of conventions in the design, it will be an added benefit for the users to interpret the use of the device.
Lastly, there are also logical constraints, where natural mapping is all about. It is the logical relationship between the spatial or functional layout of components and the things that they affect or are affected by. One good example is our everyday kitchen stove top. Is it ambiguous in regards to which control switch is for which burner on yours? Do you often need to stop and think which switch to turn on for the desired burner? If you do, then a good natural mapping is lacking. Two good examples are shown below.
When a device has many switches and controls, it can be a challenge to have a good design. For example, a typical audio mixing control has hundreds of switches that are identical to one another tightly lay out on the panel. One solution to this grouping problem is to set the switches for one set of functions apart from the switches that control other functions or user different types of switches. Applying different control coding method can help a lot. This includes, but not limited to, shape, texture, size, location, color, and label.
Good coding can prevent errors, but we are only humans and we do make errors at times. The two fundamental categories are mistakes and slips. Mistakes result from conscious deliberations when the users form the wrong goal. On the other hand, slips result from automatic behavior when subconscious actions suddenly take the wrong path away from reaching our goal. When the users from an appropriate goal but mess up in the performance, a slip has been made. Slips are more likely when people are distracted, bored, involved in other activities, under extra stress, or otherwise not inclined to pay full attention to the task at hand.
Norman has pointed out six different categories of slips:
With a good interface design, many mistakes can be avoided. However, slips are unavoidable. Here is what Norman thinks a designer should be aware of: If an error is possible, someone will make it. The designer must assume that all possible errors will occur and design so as to minimize the chance of the error in the first place, or its effects once it gets made. Errors should be easy to detect, they should have minimal consequences, and, if possible, their effects should be reversible.
Norman further elaborates on what the designers should do:
Norman's ideas of dealing with errors are that built-in warning features should be avoided because they can go off in error, disrupting proper behavior, and can be distracting and inconvenient. One suggestion is to use forcing functions, which are situations in which the actions are constrained so that failure at one stage prevents the next step from happening. But Norman warns designers that if a forcing function is used, make sure that it works right, is reliable, and distinguishes legitimate violations from illegitimate ones.
Forcing functions are usually used to prevent accidents. Three such methods are interlock, lockin, and lockout. An interlock forces operations to take place in proper sequence. A lockin keeps an operation active, preventing someone from prematurely stopping it. And a lockout device is one that prevents someone from entering a place that is dangerous, or prevents an event from occurring. Although the idea of forcing functions are good, they are almost always a nuisance in normal usage. Designer should minimize the nuisance value while retaining the safety, forcing-function mechanism, to guard against the occasional tragedy.
The proper philosophy that Norman thinks a designer should have for dealing with errors is that the entire interaction should be treated as a cooperative endeavor between person and machine, one in which misconceptions can arise on either side. And the designers should keep that in mind as they deal with the possible problems that can arise during the use of their systems.
User-centered design should be the fundamental philosophy that designers should go by. However, too often they are not. Designers have a lot of pressure from many other factors. Demands of time, pressure to be distinctive, and the curse of individuality to name a few. Designers also must please their clients, who are often not the end users.
There are also two temptations that the designers have that lead to products that are overly complex. One is what Norman calls creeping featurism, which is the tendency to add to the number of features that a device can do, often extending the number beyond all reason. To overcome this, one is avoidance, allowing only the absolutely necessary functions. The other is to organize, modularize, and to use the strategy of divide and conquer to lay out the functions.
The other temptation that Norman has mentioned is the worshipping of false images. It refers to the designers and users' temptation to worship complexity even though the extra functionalities will not be utilized. If we, the users, keep on buying such devices, we will be encouraging the designers and/or manufacturers to build these fancy equipments that is nearly impossible to use.
In one of his talks, Norman mentions that the world of industry is driven by the business model: what sells. Features are dictated by marketing, which says, 'Everyone else has these features so we have to add them, but we want them in red, green, blue and rectangular as well." He goes on and says that people in power are primarily driven by their perception of the marketplace, that if we are not careful, Hollywood standards will dominate the information industry -- low standards in culture, low standards in content, high standards in glitter, and a price for everything. If we want to do things right, Norman states that the theory of Human-Computer Interaction is the easy part. He always has the set of principles for user-centered design:
In his recent book, Things That Make Us Smart, Norman mentions that technology can indeed enhance human intelligence, but only if it is properly built to fit human abilities and needs. All too often it is people who must conform to the technology. The proper way is, of course, for technology to conform to people.