About usability and attention
16 марта 2011 | admin | Theory
What is attention?
Attention enables us to process information about our environment. We recognize things only when we give some attention to them. Attention can be compared to flashlight, which we direct at an object to single it out. After we focused the flashlight on the object we start analyzing what we see.
Attention is «... the taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought…… it requires withdrawal from some things in order to deal effectively with others.»
- William James, 1890
We can have control over our attention. This type of attention is called unconditioned and intentional. For instance, when we are in class, we make ourselves listen to the professor and look at the blackboard with formulas. Or when we are looking for a book in the library we deliberately pay attention to book titles. We can use unconditioned attention for filtering irrelevant information. We are focusing on search of a certain form, color or word. For instance when we are looking for a meat dish on the menu, we will be searching for a picture displaying meat or a word “chicken”, “pork” or “mutton” while ignoring other information (price, weight, ingredients). Our motives, expectations and intentions also influence our attention. External signals, other objects which are within our perception, influence our attention as well. For instance a loud clap makes us turn our head in the direction of the supposed source of the sound, a blinking icon in the corner of the display immediately draws our look. This type of attention is called spontaneous and is controlled by external stimuli. Psychologists define such type of attention as unconditioned. Attention has a great influence over working efficiency. Especially over work, connected with HCI. Software or web site interface should manage user’s attention, helping perceive only the information which is relevant here and now.
Types of attention
There are three types of attention:
1. Selective attention
This type of attention is sometimes called tunnel attention. It occurs, when we pay our attention to a stimulus or a task so much, that we ignore all other stimuli and objects. A programmer, absorbed in program code writing, a gamer, browsing the web or a driver, totally concentrated on the road can easily miss a question, asked by someone else.
2. Focused attention
This type can be called more effective selective attention because we deliberately stop paying attention to stimuli in order to complete the task performance. For instance, an office clerk deliberately stops paying attention to conversation between his colleagues in order to continue an important business talk. Or a user, who is deliberately ignoring new email notification in order to finish and send an e-mail. A telephone talk in the first case and a letter in the second case are in the sphere of focused attention, other stimuli were deliberately eliminated out of sight.
3. Distributed attention
There are situations when it’s impossible to focus attention on one task because other stimuli are distracting us. For instance if we hear somebody talking about us, while we are having a conversation with others, it’s will be hard to keep focusing on your own conversation. Some computer tasks require users to focus on several things. It decreases efficiency and user’s working capacity.
Importance of attention for interface design and usability
Understanding of how attention works allows to create efficient user interfaces. The following factors influence how a user perceives interface information:
2.goals and tasks
3. knowledge and experience
4. message contents
5. unusualness of message
Interface should help a user focus his attention on important information. Text position, its size, color and contrast – all these properties can play a role of a hint, which will draw user’s attention to something relevant.
There are ways to draw user’s attention to links or functions, which are critical for task performance and business goals. Paid subscription to a dating site is a great example of a critical function for business goals, “more” link is an example of a link, which helps user orientate and get the whole text of an article, i.e. perform his task.
It’s very important to know, which elements should be accompanied by a visual hint, when and how. It will help to avoid a situation when all elements are attracting attention and the screen looks like white noise. All the information in this case is interchangeable and a user can miss something that from your point of view is very important, something that should draw attention in the first place.
A very common mistake here is to put an important business message inside a big colorful square. Users already know how to ignore banner ads and selectively pay attention only to the elements and functions, which are relevant to them. This effect is called “banner blindness”. Overloading with hints on a single page can level positive effect of drawing attention because hints are going to compete with each other (the page will sound like a chorus). Users can also get used to these hints if they are used often and without visible diversity. It’s especially important for design of dialogues with warnings or critical error reports.
Breaking of common stereotypes and agreements can lead to a situation where users simply miss available functions. For instance navigation links and menu points should be always accompanied by visual hints, otherwise a user can miss the whole section of the site. Buttons referring to important actions (e.g. “register” or “send”) not only should resemble button, but stand out of other elements. It’s very important to know how a user reacts to different sensor stimuli. Besides, every user has a number of elements he filters as insignificant and irrelevant. To effectively manage user actions it’s important to know both the first and the second factor.
Assistance to focused attention
Completing of some tasks requires focused attention from the user. Secondary elements, competing with the main ones, should be eliminated from the interface. For instance, animated banner ads can really disturb a user who is trying to write an important e-mail. Just like extra variants of action can confuse a user and slow down task performance. In desktop interface application a modal window (e.g. standard print dialog) helps focus user attention on a limited number of variants, which are important at the moment (and hide the rest of the functional). A user will not even notice that his attention is being manipulated. This is one of the purposes of user oriented design: the less they think about the interface, the more they focus on the task they are performing with the help of software or web site. Focused attention may ad should be used to draw attention to system safety violation, critical errors and notifications. For instance when a user tries to save a Word document under the file name that already exists, he will see a modal notification, which draws user attention and prevents him from focusing on something else. External visual guidelines and interface elements (e.g. a frame around error notification) help a user focus on important information and prevent a serious error.
Search of information with the help of attention
A user often has a task of finding some important information in the “noised” interface. We use our attention for that: we select and separate something we need from all other information. To simplify this search task we can use one-one correspondents between visual properties of information (e.g. color, form, position on the screen) and information itself. In this case the user attention will be controlled by the user himself and not by the interface. It can significantly increase work efficiency, as the user is able to quickly specify the settings of his search request and momentarily get the answer.
Designing interfaces for distributed attention.
There are situations when you have to pay attention to several things at once. Ability to distribute attention explains why we are able to do several things at once, e.g. watch news and talk on the phone. But attention is a limited resource, it can be distributed up to a certain limit. The number of various stimuli, which a user should react to in order to perform a task, is called mental workload. The higher it is, the more chances that a user will make an error in one or all tasks that he is trying to perform simultaneously (trying to kill two birds with one stone).
When designing an interface it’s important to keep user’s mental workload on constant and comfortable level for the user. For these purposes the task is divided into steps or subtasks. If the subtask requires following two or more stimuli or simultaneous processing of different information branches, its size have to be reduced (by eliminating everything irrelevant out of sight).
Distribution of attention is a critical factor for tasks demanding special alertness (i.e. tasks, where a user has to watch interface changes over a long time). Examples: air traffic control, security system control, nuclear station management.
Distribution of attention and interference
Interface designers should keep in mind that two stimuli can conflict with each other preventing us from controlling our attention. Such interference may occur due to overload of attention capacity (because of a complicated task). But there are other reasons. For instance, if two stimuli have the same modality (e.g. two audiostreams) they are more likely to confront each other. There’s so called Stroop effect, when two stimuli have the same contents or meaning.
Human short term memory has cognitive structure, which is called articular cycle. This structure is responsible for repeating sound stimuli approximately every 2 seconds (it usually occurs in our mind). That’s why any task, where sounds are used, prevents us from remembering text or verbal information (because of the conflict between articular cycle and external sound stimuli). When two stimuli, screen elements or actions are competing for the same cognitive resource they start interference with each other. It can lead to mistakes. We should design such interfaces that allow a user to focus his attention on important information. Stimuli, which can cause interference, should be isolated. It’s especially urgent if task performance requires distributed attention.
Interface in a noisy environment should not rely just on sound feedback. If you can’t do without sound feedback, choose easily distinguishable tone, pitch and duration of sounds.
Long detained unconditional attention
Many users use computer technologies to improve their work efficiency. Systems, critical for time and security, depend on computers a lot. If a user has to watch computer feedback for a long time such dependence can be very strong. For example: stock exchange management systems, air traffic management, security systems at drilling rigs, hydro power station or plant. After some time the operator gets tired and it’s becoming more and more difficult to focus his attention on interface elements. Critical visual and sound hints can be missed, which increases chances for making a mistake. Designers of such interfaces should understand the nature of the task and possible limits to human attention. Designers must make sure that new critical information is able to quickly draw operator’s attention. Besides, load of operator’s attention should be minimized to the best possible limit.
Central and peripheral attention
When discussing selective, focused and distributed attention, it’s very important to identify where visual attention is pointed at every given moment. It’s especially vital for the part of interface which is projected to the central fossa (central part of retina where most photoreceptors are concentrated) or in other words, that part of interface, which is in sight of the user. This area is often called UFOV (useful field of view). When a user uses selective or focused visual attention, he uses UFOV for interface scanning or focusing on some part of interface. UFOV is usually located between 1 and 4 degree of visual angle and this fact should be considered in tasks, where information located outside this area may be missed.
Interface designers should understand the principles of … eyesight and visual hints, which can be used to draw attention to interface area outside UFOV. … area of our eyesight is most sensitive to visual hints, based on movement, blinking and rapid contrast changing.
Correctly designed interface can increase work efficiency due to skillful management of user’s attention. You should keep in mind that attention requirements of the task do not exceed the limit.