chapter 1 the psychopathology of everyday things if I were placed in the cockpit of a modern jet airliner my inability to perform well would neither surprised nor bother me but why should I have trouble with doors and light switches water faucets and stoves doors I can hear the listeners saying you have trouble opening doors yes I push doors that are meant to be pulled pulled or is that should be pushed and walk into doors that neither pole nor push but slide moreover I see others having the same troubles unnecessary troubles my problems with doors have become so well-known that confusing doors are often called Norman doors imagine becoming famous for doors that don't work right I'm pretty sure that's not will my parents plan for me put Norman doors into your favorite search engine be sure to include the quote marks it makes for fascinating reading how can such a simple thing as a door be so confusing a door would seem to be about a simple a device as possible there's not much you can do to a door you couldn't open it or shut it suppose you are in an office building walking down a quarter you come to a door how does it open should you push or pull on the left or the right maybe the door slides if so in which direction I have seen doors that slide to the left to the right and even up into the ceiling the design of the door should indicate how to work it without any need for signs certainly without any need for trial and error a friend told me of the time he got trapped in the doorway of a post office in a European city the entrance was an imposing row of six glass swinging doors followed immediately by a second identical row that's a standard design it helps reduce the airflow and thus maintain the indoor temperature of the building there was no visible Hardware obviously the doors could swing in either direction all a person had to do was push the side of the door and enter my friend pushed on one of the outer doors it swung inward and he entered the bill then before he could get to the next row of doors he was distracted and turned around for an instant he didn't realize it at the time but he had moved slightly to the right so when he came to the next door and pushed it nothing happened hmm he thought must be locked so he pushed the side of the adjacent door nothing puzzled my friend decided to go outside again he turned around and pushed against the side of a door nothing he pushed the adjacent door nothing the door he had just entered no longer worked he turned around once more and tried the inside doors again nothing concern then mild panic he was trapped just then a group of people on the other side of the entranceway to my friends right passed easily through both sets of doors my friend hurried over to follow their path how could such a thing happen a swinging door has two sides one contains the supporting pillar and the hinge the other is unsupported to open the door you must push or pull on the unsupported edge if you push on the hinge side nothing happens in my friends case he was in a building where the designer aimed for beauty not utility no distracting lines no visible pillars no visible hinges so how can the ordinary user know which side to push on while distracted my friend had moved toward the invisible supporting pillar so he was pushing the doors on the hinge side no wonder nothing happened attractive doors stylish probably won a design prize two of the most important characteristics of good design are discoverability and understanding discoverability is it possible to even figure out what actions are possible and where and how to perform them understanding what does it all mean how is the product supposed to be used what do all the different controls and settings mean the doors in the story illustrate what happens when discoverability fails whether the device is a door or a stove a mobile phone or a nuclear power plant the relevant components must be visible and they must communicate the correct message what actions are possible where and how should they be done with doors that push the designer must provide signals that naturally indicate where to push these need not destroy the aesthetics put a vertical plate on the side to be pushed or make the supporting pillars visible the vertical plate and supporting pillars are natural signals naturally interpreted making it easy to know just what to do no labels needed with complex devices discoverability and understanding require the aid of manuals or personal instruction we accept this if the device is indeed complex but it should be unnecessary for simple things many products defy understanding simply because they have too many functions and controls I don't think that simple home appliances stoves washing machines audio and television sets should look like Hollywood's idea of a spaceship control room they already do much to our consternation faced with a bewildering array of controls and displays we simply memorize one hour to fix settings to approximate what is desired in England I visited a home with a fancy new Italian washer/dryer combination with super duper multi symbol controls all to do everything anyone could imagine doing with the washing and drying of clothes the husband an engineering psychologist said he refused to go near it the wife a physician said she simply memorized one setting and tried to ignore the rest I asked to see the manual it was just as confusing as the device the whole purpose of the design is lost the complexity of modern devices all artificial things are designed whether it is the layout of furniture in a room the paths to a garden or forest or the intricacies of an electronic device some person or group of people had to decide upon the layout operation and mechanisms not all design things involve physical structures services lectures rules and procedures and the organ is structures of businesses and governments do not have physical mechanisms but their rules of operation have to be designed sometimes informally sometimes precisely recorded and specified but even though people have designed things since prehistoric times the field of design is relatively new divided into many areas of specialty because everything is designed the number of areas is enormous ranging from clothes and furniture to complex control rooms and bridges this book covers everyday things focusing on the interplay between technology and people to ensure that the products actually fulfill human needs while being understandable and usable in the best of cases the products should also be delightful and enjoyable which means that not only must the requirements of engineering manufacturing and ergonomics be satisfied but attention must be paid to the entire experience which means the aesthetics of form and the quality of interaction the major areas of design relevant to this book are industrial design interaction design and experience design none of the fields are well defined but the focus of the efforts does vary with industrial designers emphasizing form and material interactive designers emphasizing understandability and usability and experience designers emphasizing the emotional impact thus industrial design the professional service of creating and developing concepts and specifications that optimize the function value and appearance of products and systems for the mutual benefit of both user and manufacturer from the industrial design Society of America's website interaction design the focus is upon how people interact with technology the goal is to enhance people's understanding of what can be done what is happening and what has just occurred interaction design draws upon principles of psychology design art and emotion to ensure a positive enjoyable experience experience design the practice of designing products processes services events and environments with a focus placed on the quality and enjoyment of the total experience design is concerned with how things work how they are controlled in the nature of the interaction between people and technology when done well the results are brilliant pleasurable products when done badly the products are unusable leading the great frustration and irritation or they might be usable but force us to behave the way the product wishes rather than as we wish machines after all are conceived designed and constructed by people by human standards machines are pretty limited they do not maintain the same kind of rich history of experiences that people have in common with one another experiences that enable us to interact with others because of this shared understanding instead machines usually follow rather simple rigid rules of behavior if we get the rules wrong even slightly the machine does what it is told no matter how insensible and illogical people are imaginative and creative filled with common sense that is a lot of valuable knowledge built up over years of experience but instead of capitalizing on these strengths machines require us to be precise and accurate things we are not very good at machines have no leeway or common sense moreover many of the rules followed by a machine are known only by the Machine and its designers when people fail to follow these bizarre secret rules and the Machine does the wrong thing its operators are blamed for not understanding the machine for not following its rigid specifications with everyday objects the result is frustration with complex devices in commercial and industrial processes the resulting difficulties can lead to accidents injuries and even deaths it is time to reverse the situation to cast the blame upon the machines and their design it is the Machine and its design that are at fault it is the duty of machines and those who designed them to understand people it is not our duty to understand the arbitrary meaningless dictates of machines the reasons for the deficiencies in human machine interaction numerous some come from the limitations of today's technology some come from self-imposed restrictions by the designers often to hold down cost but most of the problems come from the complete lack of understanding of the design principles necessary for effective human machine interaction why this deficiency because much of the design is done by engineers who are experts in technology but limited in their understanding of people we are people ourselves they think so we understand people but in fact we humans are amazingly complex those who have not studied human behavior often think it is pretty simple engineers moreover make the mistake of thinking that logical explanation is sufficient if only people would read the instructions they say everything would be all right engineers are trained to think logically as a result they come to believe that all people must think this way and they design their machines accordingly when people have trouble the engineers are upset but often for the wrong reason what are these people doing they will wonder why are they doing that the problem with the designs of most engineers is that they are too logical we have to accept human behavior the way it is not the way we would wish it to be I used to be an engineer focused upon technical requirements quite ignorant of people even after I switched into psychology and cognitive science I still maintained my engineering emphasis upon logic and mechanism it took a long time for me to realize that my understanding of human behavior was relevant to my interest in the design of technology as I watched people struggle with technology it became clear that the difficulties were caused by the technology not the people I was called upon to help analyze the American nuclear power plant accident at Three Mile Island the island name comes from the fact that it is located on a river three miles south of Middletown in the state of Pennsylvania in this incident a rather simple mechanical failure was misdiagnosed this led to several days of difficulties in confusion total destruction of the reactor and a very close call to a severe radiation release all of which brought the American nuclear power industry to a complete halt the operators were blamed for these failures human error was the immediate analysis but the committee Amazon discovered that the plants control rooms were so poorly designed that error was inevitable design was at fault not the operators the morale was simple we were designing things for people so we needed to understand both technology and people but that's a difficult step for many engineers machines are so logical so orderly if we didn't have people everything would work so much better yep that's how I used to think my work with that committee changed my view of design today I realize that design presents a fascinating interplay of Technology and psychology that the designers must understand both engineers still tend to believe in logic they often explained to me in great logical detail why their designs are good powerful and wonderful why are people having problems they wonder you are being too logical I say you are designing for people the way you would like them to be not the way they really are when the engineers object I ask whether they have ever made an error perhaps turning on or off the wrong light or the wrong stove burner oh yes they say but those were errors that's the point even experts make errors so we must design our machines on the assumption that people will make errors chapter 5 provides a detailed analysis of human error human centered design people are frustrated with everyday things from the ever increasing complexity of the automobile dashboard to the increasing automation in the home with its internal networks complex music video and game systems for entertainment and communication and the increasing automation in the kitchen everyday life sometimes seems like a never-ending fight against confusion continued frustration and a continuous cycle of updating and maintaining our belongings in the multiple decades that have elapsed since the first edition of this book was published design has gotten better there are now many books and courses on the topic but even though much has improved the rapid rate of Technology change outpaces the advances in design new technologies new applications and new methods of interaction are continually arising and evolving new industry spring up each new development seems to repeat the mistakes of the earlier ones each new field requires time before it too adopts the principles of good design and each new invention of technology or interaction technique requires experimentation and study before the principles of good design can be fully integrated into practice so yes things are getting better but as a result the challenges are ever-present the solution is human centered design HCD an approach that puts human needs capabilities and behavior first then designs to accommodate those needs capabilities and ways of behaving good design starts with an understanding of psychology and technology good design requires good communication especially from machine to person indicating what actions are possible what is happening and what is about to happen communication is especially important when things go wrong it is relatively easy to design things that work smoothly and harmoniously as long as things go right but as soon as there is a problem or a misunderstanding the problems arise this is where good design is essential designers need to focus their attention on the cases where things go wrong not just and when things work as planned actually this is where the most satisfaction can arise when something goes wrong but the Machine highlights the problems then the person understands the issue takes the proper actions and the problem is solved when this happens smoothly the collaboration of person and device feels wonderful human centered design is a design philosophy it means starting with a good understanding of people and the needs that the design is intended to meet this understanding comes about primarily through observation for people themselves are often unaware of their true needs even unaware of the difficulties they are encountering getting the specification of the thing to be defined is one of the most difficult parts of the design so much so that the HCD principle is to avoid specifying the problem as long as possible but instead to iterate upon repeated approximations this is done through rapid tests of ideas and after each test modifying the approach and the problem definition the results can be products that truly meet the needs of people doing HCD within the rigid time budget and other constraints of Industry can be a challenge chapter six examines these issues where does HCD fit into the earlier discussion of the several different forms of design especially the areas called industrial interaction and experience design these are all compatible HCD is a philosophy and a set of procedures whereas the others our areas of focus please refer to the downloadable PDF table 1.1 included with this audio book the philosophy and procedures of HCD add deep consideration and study of human needs to the design process whenever the product or service whatever the major focus fundamental principles of interaction great designers produce pleasurable experiences experience note the word engineers tend not to like it it is too subjective but when I ask them about their favorite automobile or test equipment they will smile delightedly as they discuss the fit and finish the sensation of power during acceleration their ease of control while shifting or steering or the wonderful feel of the knobs and switches on the instrument those are experiences experience is critical for it determines health fondly people remember their interactions was the overall experience positive or was it frustrating and confusing when our home technology behaves in an uninterpretable fashion we can become confused frustrated and even angry all strong negative emotions when there is understanding it could lead to a feeling of control of mastery and of satisfaction or even pride all strong positive emotions cognition and emotion are tightly intertwined which means that the designers must design with both in mind when we interact with the product we need to figure out how to work it this means discovering what it does how it works and what operations are possible discoverability discoverability results from appropriate application of five fundamental psychological concepts covered in the next few chapters affordances signifiers constraints mappings and feedback but there is a sixth principle perhaps most important of all the conceptual model of the system it is the conceptual model that provides true understanding so I now turn to these fundamental principles starting with affordances signifiers mappings and feedback then moving to conceptual models constraints are covered in chapters 3 & 4 affordances we live in a world filled with objects many natural the rest artificial everyday we encounter thousands of objects many of them new to us many of the new objects are similar to ones we already know but many are unique yet we manage quite well how do we do this why is it that when we encounter many unusual natural objects we know how to interact with them why is this true with many of the artificial human-made objects we encounter the answer lies with a few basic principles some of the most important of these principles come from the consideration of affordances the term affordance refers to the relationship between a physical object and a person or for that matter any interacting agent whether animal or human or even machines and robots an affordance is a relationship between the properties of an object and the capabilities of the agent that determined just how the object could possibly be used a chair of Ford's is for support and therefore a Ford sitting most chairs can also be carried by a single person they afford lifting but some can only be lifted by a strong person or by a team of people if young are relatively weak people cannot lift the chair then for those people the chair does not have that affordance it does not afford lifting the presence of an affordance is jointly determined by the qualities of the object and the abilities of the agent that is interacting this relational definition of affordance gives considerable difficulty to many people we are used in thinking that properties are associated with objects but affordance is not a property an affordance is a relationship whether an affordance exists depends upon the properties of both the object and the agent glass affords transparency at the same time its physical structure blocks the passage of most physical objects as a result glass of poured seeing through and support but not the passage of air or most physical objects atomic particles can pass their glass the blockage of passage can be considered an anti affordance the prevention of interaction to be effective affordances and anti affordances have to be discoverable perceivable this poses a difficulty with glass the reason we like glass is its relative invisibility but this aspect so useful in the normal window also hides its anti affordance property a blocking passage as a result birds often try to fly through windows and every year numerous persons injure themselves when they walk or run through closed glass doors or large picture windows if an affordance or anti affordance cannot be perceived some means of signaling its presence is required I call this property a signifier discussed in the next section the notion of affordance and the insights it provides originated with JJ Gibson an eminent psychologist who provided many advances to our understanding of human perception I had interacted with him over many years sometimes informal conferences and seminars but most fruitfully over many bottles of beer late at night just talking we disagreed about almost everything I was an engineer who became a cognitive psychologist trying to understand how the mind works he started off as a gestalt psychologists but then developed an approach that is today named after him Gibbs Sounion psychology and ecological approach to perception he argued that the world contained the clues and that people simply pick them up through direct perception I argue that nothing could be direct the brain had to process the information arriving at the sense organs to put together a coherent interpretation nonsense he'd loudly proclaimed it requires no interpretation it is directly perceived and then he would put his hand to his ears and with a triumphant flourish turn off his hearing aids my encounter arguments would fall upon deaf ears literally when I pondered my question how do people know how to act when confronted with a novel situation I realized that a large part of the answer lay in Gibson's work he pointed out that all the senses work together that we pick up information about the world by the combined result of all of them information pick up was one of his favorite phrases and Gibson believed that the combined information picked up by all of our sensory apparatus sight sound smell touch balance kinesthetic acceleration body position determines our perceptions without the need for internal processing or cognition although he and I disagreed about the role played by the brains internal processing his brilliance was in focusing attention on the rich amount of information present in the world moreover the physical objects conveyed important information about how people could interact with them a property he named affordance affordances exist even if they are not visible for designers their visibility is critical visible affordances provide strong clues to the operations of things a flat plate mounted on a door affords pushing knobs afford turning pushing or pulling slots for inserting things into balls are for throwing or bouncing perceived affordances help people figure out what actions are possible without the need for labels or instructions I called the signalling component of affordances signifiers signifiers our affordances important to designers the first edition of this book introduced the term affordances to the world of design the design community loved the concept and affordances soon propagated into the instruction and writing about design I soon found mention of the term everywhere alas the term became used in ways that had nothing to do with the original many people find affordances difficult to understand because they are relationships not properties designers deal with fixed properties so there is a temptation to say that the property is an affordance but then it's not the only problem with the concept of affordances designers have practical problems they need to know how to design things to make them understandable they soon discovered that when working with the graphical designs for electronic displays they needed a way to designate which parts could be touched slid upward downward or sideways or tapped upon the actions can be done with a mouse stylus or fingers some systems responded to body motions gestures and spoken words with no touching of any physical device how could designers describe what they were doing there was no word that fits so they took the closest existing word affordance soon designers were saying such things as I put an affordance there to describe why they displayed a circle on the screen to indicate where the person should touch whether by mouse or by finger no I said that is not an affordance that is a way of communicating where the touch should be you are communicating where to do the touching the importance of touching exists on the entire screen you are trying to signify where the touch should take place that's not the same thing as saying what action is possible not only did my explanation fail to satisfy the design community but I myself was unhappy eventually I gave up designers needed a word to describe what they were doing so they chose affordance what alternative do they have I decided to provide a better answer signifiers affordances determine what actions are possible signifiers communicate where the action should take place we need both people means some way of understanding the product or service they wish to use some sign of what it is for what is happening and what the alternative actions are people search for clues for any sign that might help them cope and understand it is the sign that is important anything that might signify meaningful information designers need to provide these clothes what people need and what designers must provide are signifiers good design requires among other things good communication of the purpose structure and operation of the device to the people who use it that is the role of the signifier the term signifier has had a long and illustrious career and the exoteric field of semiotics the study of signs and symbols but just as I appropriated affordance to use in design and a man are somewhat different than its inventor had intended I use signifier in a somewhat different way than it is used in semiotic s-- for me the term signifier refers to any mark or sound any perceivable indicator that communicates appropriate behavior to a person signifiers can be deliberate and intentional such as the sign push on a door but they may also be accidental and unintentional such as our use of the visible trail made by previous people walking through a field or over a snow-covered terrain to determine the best path or how we might use the presence or absence of people waiting at a train station to determine whether we have missed the train I explain these ideas in more detail in my book living with complexity the signifier is an important communication device to the recipient whether or not communication was intended it doesn't matter whether the useful signal was deliberately placed or whether it is incidental there is no necessary distinction why should it matter whether a flag was placed as a deliberate cue to wind direction as is done at airports or on the masts of sailboats or was there an advertisement or symbol of pride in one's country as is done on public buildings once I interpret a Flags motion to indicate wind direction it does not matter why it was placed there consider a bookmark a deliberately placed signifier of one's place in reading a book but the physical nature of books also makes a bookmark an accidental signifier for its placement also indicates how much of the book remains most readers have learned to use this accidental signifier to aid in their enjoyment of the reading with few pages left we know the end is near and if the reading is torturous as in the school assignment one can always console oneself by knowing there are only a few more pages to get through electronic book readers do not have the physical structure of paper books so unless the software designer deliberately provides a clue they do not convey any signal about the amount of text remaining whatever their nature planned or accidental signifiers provide valuable clues as to the nature of the world end of social activities for us to function in this social technological world we need to develop internal models of what things mean of how they operate we seek all the clues we can find to help in this enterprise and in this way we are detectives searching for whatever guidance we might find if we are fortunate thoughtful designers provide the clues for us otherwise we must use our own creativity and imagination affordances perceived affordances and signifiers have much in common so let me pause to ensure that the distinctions are clear affordances represent the possibilities in the world for how an agent a person animal or machine can interact with something some affordances are perceivable others are invisible signifiers are signals some signifiers are signs labels and drawings placed in the world such as the signs labeled push pull or exit on doors or arrows and diagrams indicating what is to be acted upon or in which direction to gesture or other instructions some signifiers are simply the perceived affordances such as the handle of a door or the physical structure of a switch note that some perceived affordances may not be real they may look like doors or places to push or an impediment to entry when in fact they are not these are misleading signifiers often times accidental but sometimes purposeful as when trying to keep people from doing actions for which they are not qualified or in games where one of the challenges is to figure out what is real and what is not my favorite example of a misleading signifier is a row of vertical pipes across a service road that I once saw in a public park the pipes obviously blocked cars and trucks from driving on that road there were good examples of anti affordances but to my great surprise I saw a park vehicle simply go through the pipes huh I walked over and examined them the pipes were made of rubber so vehicles could simply drive right over them a very clever signifier signaling a blocked road via an apparent anti affordance to the average person but permitting passage for those who knew to summarize affordances are the possible interactions between people and the environment some affordances are perceivable others are not perceived affordances often act as signifiers but they can be ambiguous signifiers signal things in particular what actions are possible and how they should be done signifiers must be perceivable else they fail to function in design signifiers are more important than affordances for they communicate how to use the design a signifier can be words a graphical illustration or just a device whose perceived affordances are unambiguous creative designers incorporate the signifying part of the design into a cohesive experience for the most part designers can focus upon signifiers because affordances and signifiers are fundamentally important principles of good design they show up frequently in the pages of this book whenever you see hand lettered signs pasted on doors switches or products trying to explain how to work them what to do and what not to do you are all so looking at poor design affordances and signifiers a conversation a designer approaches his mentor he is working on a system that recommends restaurants to people based upon their preferences and those of their friends but in his tests he discovered that people never used all of the features why not he asked his mentor with apologies to Socrates designer I'm frustrated people aren't using our application properly mentor can you tell me about it designer the screen shows the restaurant that we recommend it matches their preferences and their friends liked it as well if they want to see other recommendations all they have to do is swipe left or right to learn more about a place just swipe up for a menu or down to see if any friends are there now people seem to find the other recommendations but not the menus or their friends I don't understand mentor why do you think this might be designer I don't know should I add some affordances suppose I put an arrow on each edge and add a label saying what they do mentor that is very nice but why do you call these affordances they could already do the actions weren't the affordances already there designer yes you have a point but the affordances were invisible I made them visible mentor very true you added a signal of what to do designer yes isn't that what I said mentor not quite you called them affordances even though they afford nothing new they signify what to do and where to do it so call them by their right name signifiers designer oh I see but then why do designers care about affordances perhaps we should focus our attention on signifiers mentor you speak wisely communication is a key to good design and the key to communication is the signifier designer oh now I understand my confusion yes a signifier is what signifies it is a sign now it seems perfectly obvious meant or profound ideas are always obvious once they are understood mapping mapping is a technical term borrowed from mathematics meaning the relationship between the elements of two sets of things suppose there are many lights in the ceiling of a classroom or auditorium and a roll of light switches on the wall at the front of the room the mapping of switches to lights specifies which switch controls which light mapping is an important concept in the design and layout of controls and displays when the mapping uses spatial correspondence between the layout of the controls and the devices being controlled it is easy to determine how to use them in steering a car we rotate the steering wheel clockwise to cause the car to turn right the top of the wheel moves in the same direction as the car note that other choices could have been made in early cars steering was controlled by a variety of devices including tillers handlebars and reins today some vehicles use joysticks much as in a computer game in cars that use tillers steering was done much as one steers a boat move the tiller to the left to turn to the right tractors construction equipment such as bulldozers and cranes and military tanks that have tracks instead of wheels use separate controls for the speed and direction of each track to turn right the left track is increased in speed while the right track is slowed or even reversed this is also how wheelchair steered all of these mappings for the control of vehicles work because each has a compelling conceptual model of how the operation of the control affects the vehicle thus if we speed up the left wheel of a wheelchair while stopping the right wheel it is easy to imagine the chairs pivoting on the right wheel circling to the right in a small boat we can understand the tiller by realizing that pushing the tiller to the left causes the ship's rudder to move to the right and the resulting force of the water on the rudder slows down the right side of the boat so that the boat rotates to the right it doesn't matter whether these conceptual models are accurate what matters is that they provide a clear way of remembering and understanding the mappings the relationship between a control and its results is easiest to learn whenever there is an understandable mapping between the controls the actions and the intended result natural mapping by which I mean taking advantage of spatial analogies leads to immediate understanding for example to move an object up move the control up to make it easy to determine which control works which light in a large room or auditorium arrange the controls in the same pattern as the lights some natural mappings are cultural or biological as in the universal standard that moving the hand up signifies more moving it down signifies less which is why it is appropriate to use vertical position to represent intensity or amount other natural mappings follow from the principles of perception and allow for the natural grouping of patterning of controls and feedback groupings and proximity are important principles from Gestalt psychology that can be used to map controls to function related controls should be grouped together controls should be close to the item being controlled note that there are many mappings that feel natural but in fact are specific to a particular culture what is natural for one culture is not necessarily natural for another in Chapter three I discussed how different cultures view time which has important implications for some kinds of mappings a device is easy to use when the set of possible actions is visible when the controls and displays exploit natural mappings the principles are simple but rarely incorporated into design good design takes care planning thought and an understanding of how people behave feedback ever watch people at an elevator repeatedly push the UP button or repeatedly push the pedestrian button at a Street crossing never drive to a traffic intersection and wait an inordinate amount of time for the signals to change wondering all the time whether the detection circuits noticed your vehicle a common problem with bicycles what is missing in all these cases is feedback some way of letting you know that the system is working on your request feedback communicating the results of an action is a well-known concept from the science of control and information theory imagine trying to hit a target with the ball when you cannot see the target even a simpler task is picking up a glass with the hand requires feedback to aim the hand properly to grasp the glass and to lift it a misplaced hand will spill the contents too hard a grip will break the glass and too weak grip will allow it to fall the human nervous system is equipped with numerous feedback mechanisms including visual auditory and touch sensors as well as vestibular and proprioceptive systems that monitor body position and muscle and limb movements given the importance of feedback it is amazing how many products ignore it feedback must be immediate even a delay of a tenth of a second can be disconcerting if the delay is too long people often give up going off to do other activities this is annoying to the people but it can also be wasteful of resources when the system spends considerable time and effort to satisfy the requests all need of mine that the intended recipient is no longer their feedback must also be informative many companies tried to save money by using inexpensive lights or sound generators her feedback these simple light flashes or beeps are usually more annoying than useful they tell us that something has happened but convey very little information about what has happened and then nothing about what we should do about it when the signal is auditory in many cases we cannot even be certain which device has created the sound if the signal is a light we may miss it unless our eyes are on the correct spot at the correct time poor feedback can be worse than no feedback at all because it is distracting uninformative and in many cases irritating and anxiety provoking too much feedback can be even more annoying than too little my dishwasher likes to beep at 3:00 a.m. to tell me that the wash is done defeating my goal of having it work in the middle of the night so as to not disturb anyone and to use less expensive electricity but worst of all is inappropriate uninterpretable feedback the air station caused by a backseat driver is well enough known that it is the staple of numerous jokes backseat drivers are often correct but their remarks and comments can be so numerous and continuous that instead of helping they become an irritating distraction machines that give too much feedback are like backseat drivers not only is it distracting to be subjected to continual flashing lights text announcements spoken voices or beeps and Boop's but it can be dangerous too many announcements cause people to ignore all of them or whenever possible disable all of them which means that critical and important ones are apt to be missed feedback is essential but not when it gets in the way of other things including a calm and relaxing environment poor design of feedback can be a result decisions aimed at reducing costs even if they make life more difficult for people rather than use multiple signal lights informative displays or rich musical sounds with varying patterns the focus upon cost reduction forces the design to use a single light or sound to convey multiple types of information if the choice is to use the light then one flash might mean one thing to rapid flash is something else a long flash might signal yet another state and the long flash followed by a brief one yet another if the choice is to use a sound quite often the least expensive sound device is selected one that can only produce a high-frequency beep just as with the lights the only way to signal different states of the machine is by beeping different patterns what do all these different patterns mean how can we possibly learn and remember them it doesn't help that every different machine uses a different pattern of lights or beeps sometimes with the same patterns meaning contradictory things for different machines all the beeps sound alike so it often isn't even possible to know which machine is talking to us feedback has to be planned all actions need to be confirmed but in a manner that is unobtrusive feedback must also be prioritized so that unimportant information is presented in an unobtrusive fashion but important signals are presented in a way that does capture attention when there are major emergencies then even important signals have to be prioritized when every device is signalling a major emergency nothing is gained by the resulting cacophony the continual beeps and alarms of equipment can be dangerous in many emergencies workers have to spend valuable time turning off all the alarms because the sounds interfere with the concentration required to solve the problem hospital operating rooms emergency wards nuclear power control plants airplane cockpits all can become confusing irritating and life endangering places because of excessive feedback excessive alarms and incompatible message coding feedback is essential but it has to be done correctly appropriately conceptual models a conceptual model is an explanation usually highly simplified of how something works it doesn't have to be complete or even accurate as long as it is useful the files folders and icons you see displayed on a computer screen help people create the conceptual model of documents and folders inside the computer or of apps or applications residing on the screen waiting to be summoned in fact there are no folders inside the computer those are effective conceptualizations designed to make them easier to use sometimes these depictions can add to the confusion however when reading email are visiting a website the material appears to be on the device for that is where it is displayed and manipulated but in fact in many cases the actual material is in the cloud located on some distant machine the conceptual model is of one coherent image whereas it may actually consist of parts each located on different machines that could be almost anywhere in the world this simplified model is helpful for normal usage but if the network connection to the cloud services is interrupted the result can be confusing information is still on their screen but users can no longer save it or retrieve new things their conceptual model offers no explanation simplified models are valuable only as long as the assumptions that support them hold true there are often multiple conceptual models of a product or device people's conceptual models for the way that regenerative braking in a hybrid or electrically powered automobile works are quite different for average drivers than for technically sophisticated drivers different again for whoever must service the system and yet different again for those who design the system conceptual models found in technical manuals and books for technical use can be detailed and complex the ones we are concerned with here are simpler they reside in the minds of the people who are using the product so there are also mental models mental models as the name implies are the conceptual models in people's minds that represent their understanding of how things work different people may hold different mental models of the same item indeed a single person might have multiple models of the same item each dealing with a different aspect of its operation the models can even be in conflict conceptual models are often inferred from the device itself some models are passed on from person to person some come from manuals usually the device itself offers very little assistance so the model is constructed by experience quite often these models are erroneous and therefore lead to difficulties in using the device the major clues to how things work come from their perceived structure in particular from signifiers affordances constraints and mappings hand tools for the shop gardening and the house tend to make their critical parts sufficiently visible that conceptual models of their operation and function are readily derived consider a pair of scissors you can see that the number of possible actions is limited the holes are clearly there to put something into and the only logical things that will fit our fingers the holes are both affordances they allow the fingers to be inserted and signifiers they indicate where the fingers are to go the sizes of the holes provide constraints to limit the possible fingers a big hole suggests several fingers a small hole only one the mapping between holes and fingers the set of possible operations is signified and constrained by the holes moreover the OP raishin is not sensitive to finger placement if you use the wrong fingers or the wrong hand this is our still work although not as comfortably you can figure out the scissors because they're operating parts are visible and the implications clear the conceptual model is obvious and there is effective use of signifiers affordances and constraints what happens when the device does not suggest a good conceptual model consider my digital watch with five buttons to along the top to along the bottom and one on the left side please refer to downloadable PDF figure 1.8 what is each button for how would you set the time there is no way to tell no evident relationship between the operating controls and the functions no constraints no apparent mappings moreover the buttons have multiple ways of being used two of the buttons do different things when pushed quickly or when kept depressed for several seconds some operations require simultaneous depression of several of the buttons the only way to tell how to work the watch is to read the manual over and over again with the scissors moving the handle makes the blades move the watch provides no visible relationship between the buttons and the possible actions no discernible relationship between the actions and the end results I really like the watch too bad I can't remember all the functions conceptual models are valuable and providing understanding and predicting how things will behave and in figuring out what to do when things do not go as planned a good conceptual model allows us to predict the effects of our actions without a good model we operate by rote blindly we do operations as we were told to do them we can't fully appreciate why what effects to expect or what to do if things go wrong as long as things work properly we can manage when things go wrong however or when we come upon a novel situation then we need a deeper understanding a good model for everyday things conceptual models need not be very complex after all Scissors pens and light switches are pretty simple devices there is no need to understand the underlying physics or chemistry of each device we own just a relationship between the controls and the outcomes when the model presented to us is inadequate or wrong or worse non-existent we can have difficulties let me tell you about my refrigerator I used to own an ordinary two compartment refrigerator nothing very fancy about it the problem was that I couldn't set the temperature properly there were only two things to do adjust the temperature of the freezer compartment and adjust the temperature of the fresh food compartment and there were two controls one labeled freezer the other refrigerator what's the problem Oh perhaps I'd better warn you the two controls are not independent the freezer control also affects the fresh food temperature and the fresh food control also affects the freezer moreover the manual warns that one should always allow 24 hours for the temperature to stabilize where they're setting the controls for the first time or making an adjustment it was extremely difficult to regulate the temperature of my old refrigerator why because the controls suggest a false conceptual model two compartments two controls which implies that each control is responsible for the temperature of the compartment that carries its name please refer to downloadable PDF table one point 10a it is wrong in fact there is only one thermostat and only one cooling mechanism one control adjust the thermostat setting the other the relative proportion of cold air sent to each of the two compartments of the refrigerator this is why the two controls interact this conceptual model is shown in Figure one point 10 B in addition there must be a temperature sensor but there is no way of knowing where it is located with the conceptual model suggested by the controls adjusting the temperature is almost impossible and always frustrating given the correct model life would be much easier why did the manufacturer suggests the wrong conceptual model we will never know in the 25 years since the publication of the first edition of this book I have had many letters from people thanking me for explaining their confusing refrigerator but never any communication for the manufacturer General Electric perhaps the designers thought the correct model was too complex that the model they were giving was easier to understand but with the wrong conceptual model it was impossible to set the controls and even though I am convinced I knew the correct model I still couldn't accurately adjust the temperatures because the refrigerator design made it impossible to discover which control was for the temperature sensor and which for the relative proportion of cold air and in which compartment the sensor was located the lack of immediate feedback for the actions did not help it took 24 hours to see whether the new setting was appropriate I shouldn't have to keep a laboratory notebook to do controlled experiments just to set the temperature of my refrigerator I am happy to say that I no longer own that refrigerator instead I have one that has two separate controls one in the fresh food compartment one in the freezer compartment each control is nicely calibrated in degrees and labeled with the name of the compartment it controls the two compartments are independent setting the temperature in one has no effect on the temperature in the other this solution although ideal does cost more but far less expensive solutions are possible with today's inexpensive sensors and motors it should be possible to have a single cooling unit with a motor controlled valve controlling the relative proportion of cold air diverted to each compartment a simple inexpensive computer chip could regulate the cooling unit and valve position so that the temperatures and the two compartments match their targets a bit more work for the engineering design team yes but the results would be worth it alas General Electric is still selling refrigerators with the very same controls and mechanisms that cause so much confusion the photograph in Figure 1.9 is from a contemporary refrigerator photographed in a store while preparing this book the system image people create mental models of themselves others the environment and the things with which they interact these are conceptual models formed through experience training and instruction these models serve as guides to help achieve our goals and an understanding the world how do we form an appropriate conceptual model for the devices we interact with we cannot talk to the designer so we rely upon whatever information is available to us what the device looks like what we know from using similar things in the past what was told to us in the sales literature by salespeople and advertisements by articles we may have read by the product website and instruction manuals I call the combined information available to us the system image when the system image is incoherent or inappropriate as in the case of the refrigerator then the user cannot easily use the device if it is incomplete or contradictory there will be trouble as illustrated in Figure one point 11 the designer of the product and the person using the product form somewhat disconnected vertices of a triangle the designers conceptual model is the designers conception of the product occupying one vertex of the triangle the product itself is no longer with the designer so it is isolated as a second vertex perhaps sitting on the user's kitchen counter the system image is what can be perceived from a physical structure that has been built including documentation instructions signifiers and any information available from websites and helplines the users conceptual model comes from the system image through interaction with the product reading searching for online information and from whatever manuals are provided the designer expects the users model to be identical to the design model but because designers cannot communicate directly with users the entire burden of communication is on the system image figure one point eleven indicates why communication is such an important aspect of good design no matter how brilliant the product if people cannot use it it will receive poor reviews it is up to the designer to provide the appropriate information to make the product understandable and usable most important is the provision of a good conceptual model that guides the user when things go wrong with a good conceptual model people can figure out what has happened and correct the things that went wrong without a good model they struggle often making matters worse good conceptual models are the key to understandable enjoyable products good communication is the key to good conceptual models the paradox of technology technology offers the potential to make life easier and more enjoyable each new technology provides increased benefits at the same time added complexities increase our difficulty and frustration with technology the design problem posed by technological advances is enormous consider the wristwatch a few decades ago watches were simple all he had to do was set the time and keep the watch wound the standard control was the stem a knob at the side of the watch turning the knob would wind the spring that provided power to the watch movement pulling out the knob and turning it rotated the hands the operations were easy to learn and easy to do there was a reasonable relationship between the turning of the knob and the resulting turning of the hands the design even took into account human error in its normal position turning the stem while in the mainspring of the clock the stem had to be pulled before I would engage the gears for setting the time accidental turns of the stem did no harm watches in olden times were expensive instruments manufactured by hand they were sold in jewelry stores over time with the introduction of digital technology the cost of watches decreased rapidly while their accuracy and reliability increased watches became tools available in a wide variety of styles and shapes and with an ever increasing number of functions watches were sold everywhere from local shops to sporting goods stores to electronic stores moreover accurate clocks were incorporated in many appliances from phones to musical keyboards many people no longer felt the need to wear a watch watches became inexpensive enough that the average person could own multiple watches they became fashion accessories where one changed the watch with each change in activity and each change of clothes in the modern digital watch instead of winding the spring we changed the battery or in the case of a solar-powered watch ensure that it gets its weekly dose of light the technology has allowed more functions the watch can give the day of the week the month or the year it can act as a stopwatch which itself has several functions a countdown timer and an alarm clock or two it has the ability to show the time for different time zones it can act as a counter and even a calculator my watch shown in Figure 1.8 has many functions it even has a radio receiver to allow it to set its time with official time stations around the world even so it is far less complex than many that are available some watches have built-in compasses and barometers accelerometers and temperature gauges some have GPS and internet receivers so they can display the weather and news email messages and the latest from social networks some have built-in cameras some work with buttons knobs motion or speech some detect gestures the watch is no longer just an instrument for telling time it has become a platform for enhancing multiple activities and lifestyles the added functions caused problems how could all these functions fit into a small wearable size there are no easy answers many people have solved the problem by not using a watch they use their phone instead a cell phone performs all the functions much better than the tiny watch while also displaying the time now imagine a future where instead of the phone replacing the watch the two will merge perhaps worn on the wrist perhaps on the head like glasses complete with display screen the home watch and components of a computer will all form one unit we will have flexible displays that show only a tiny amount of information in their normal state but that can unroll to considerable size projectors will be so small in light that they can be built into watches our phones or perhaps rings and other jewellery projecting their images onto any convenient surface or perhaps our devices won't have displays but will quietly whisper the results into our ears or simply use whatever display happens to be available the display in the seatback of cars or airplanes hotel room televisions whatever is nearby the devices will be able to do so many useful things but I fear they will also frustrate so many to control so little space for controls or signifiers the obvious solution is to learn exotic gestures or spoken commands but how will we learn and then remember them as I discussed later the best solution is for there to be agreed-upon standards so we need learn the controls only once but as I also discuss agreeing upon knees is a complex process with many competing forces hindering rapid resolution we will see the same technology that simplifies life by providing more functions in each device also complicates life by making the device harder to learn harder to use this is the paradox of technology and the challenge for the designer the design challenge design requires the cooperative efforts of multiple disciplines the number of different disciplines required to produce a successful product is staggering great design requires great designers but that isn't enough it also requires great management because the hardest part of producing a product is coordinating all the many separate disciplines each with different goals and priorities each discipline has a different perspective of the relative importance of the many factors that make up a product one discipline argues that it must be usable and understandable another that it must be attractive yet another that it has to be affordable moreover the device has to be reliable be able to be manufactured and serviced it must be distinguishable from competing products and superior in crucial dimensions such as price reliability appearance and the functions that provides finally people have to actually purchase it it doesn't matter how good a product is if in the end nobody uses it quite often each discipline believes its distinct contribution to be most important price argues the marketing representative price plus these features reliable insist the engineers we have to be able to manufacture it in our existing plants say the manufacturing representatives we keep getting service calls say the support people we need to solve those problems in the design put all that together and still have a reasonable product says the design team who is right everyone is right the successful product has to satisfy all these requirements the hard part is to convince people to understand the viewpoints of the others to abandon their disciplinary viewpoint and think of the design from the viewpoints of the person who buys the product and those who use it often different people the viewpoint of the business is also important because it does not matter how wonderful the product is if not enough people buy it if a product does not sell the company must often stop producing it even if it is a great product few companies can sustain the huge cost of keeping an unprofitable product alive long enough for its sales to reach profitability with new products this period is usually measured in years and sometimes as with the adoption of high definition television decades designing well is not easy the manufacturer wants something that can produce economically the store wants something that will be attractive to its customers the purchaser has several demands in the store the purchaser focuses on price and appearance and perhaps on prestige value at home the same person will pay more attention to functionality and usability the repair service cares about maintainability how easy is the device to take apart diagnose and service the needs of those concerned are different and often conflict nonetheless if the design team has representatives from all the constituencies present at the same time it is often possible to reach satisfactory solutions for all the needs it is when the disciplines operate independently of one another that major clashes and efficiencies occur the challenge is to use the principles of human centered design to produce positive results products that enhance lives and add to our pleasure and enjoyment the goal is to produce a great product one that is successful and that customers love it can be done