Cognitive Load and It’s Impact on Usability
What is Cognitive Load?
Cognitive load refers to the amount of mental processing power needed to use your site and it affects how easily users find content and complete tasks. Our brains have a limited amount of processing power. When the amount of incoming information exceeds this amount, our performance is impacted. We take longer to absorb and understand information, miss details, or become overwhelmed.
In the field of UX, writer Steve Krug is the one who popularized the application of cognitive load to web design. The term was originally coined by psychologists to describe the mental effort required to learn new information. Though web browsing takes less exertion than formal education, cognitive load is still important as users must learn how to use a site’s navigation, layout and forms, while juggling information relevant to their specific goal ie. budgets, timeframe.
Knowing the implications of cognitive load theory on UX can help designers understand and accommodate for mental limits and working memory to avoid cognitive barriers.
The Scientific Roots Of Cognitive Load
Cognitive Load Theory
In the 1980’s, educational psychologist John Sweller first applied cognition research to the field of instructional design. He sought the ideal learning conditions for information retention. He published Cognitive Load Theory: Learning Difficulty and Instructional Design, incorporating effective and ineffective teaching methods.
His findings on the limitations of working memory are what designers tend to find most useful. They expand on the theories of George Miller, a cognitive psychologist whose research tested the limits of short term memory. His research is responsible for the strategy of chunking, something we will address later in this article.
The key to understanding cognitive load theory is to understand working memory, the brain activity used to complete a task in the moment, sorting through external stimuli as well as drawing from long-term memory when required. Working memory and short-term memory differ slightly in that working memory handles the processing of information, whereas short-term memory is a temporary store for information that is important, but not important enough for long-term memory.
While the theory of Cognitive Load and Working Memory were originally applied in the field of education, they are extremely relevant for user experience purposes as well. The same techniques that enhance learning and information retention can also improve user experience goals.
Intrinsic vs. Extraneous Cognitive Load
The Internet is a source of information and learning, as well as a place to perform tasks and achieve goals. Intrinsic cognitive load is the effort of absorbing new information and keeping track of the desired outcome. Extraneous cognitive load however, is processing that takes up mental resources without providing any valuable result such as helping users understand content or perform tasking faster. (ie. Confusing icons, distracting CTAs, disorganization)
Cognitive Barriers vs Cognitive Load
A cognitive barrier is something that prevents a user from performing the action required to complete their goal. Most barriers are temporary and are overcome by a momentary pause and the processing of information. Though minor, they represent potential abandonment points if the user feels at an impasse.
Number of Steps
Despite being perhaps the most well known barrier, it is often misinterpreted, as the number of steps should be weighed against the length and difficulty of each step. Sometimes its better to add steps with low cognitive load rather than have less steps that are more difficult.
Length of Steps
Just like the number of steps, the length of each step should feel appropriate for a given task. We can’t adopt a blanket rule that shorter steps make better experiences when in some cases getting a large portion of a task done upfront might provide a better experience overall. Expectations come into play here, as a user might expect to spend a longer amount on a given task as opposed to other ones (ie. booking a flight vs buying an app). Users tend to prefer shorter steps that only ask them to input bite-sized bits of information, giving the sense of moving ahead quickly and accomplishment.
Difficulty of Steps
The perceived difficulty of a step is subjective and is a main concern of UX professionals. Generally, easy steps are better, however, users do tend to develop a greater sense of loyalty toward experiences they’ve invested time into as opposed to experiences that are seen as too easy. Also, by increasing difficulty, designers can actually decrease user error by causing pause and increase the quality of the converted by weeding out those not dedicated to the task and leaving the remained of those who have taken the time to respond carefully.
Cognitive Load is the amount of working memory required to achieve the user’s goal.
Number of Choices
Decision architecture is becoming an important specialty within the UX field. The most effective e-commerce sites focus on getting users to the product they’re looking for as quickly as possible, before hitting them with related products/up-sells. If there are related products or up-sells relating to a purchase, the user will be most receptive to those additional offers at that specific moment in time. Because human working memory is limited and users are susceptible to choice paralysis, its important to simplify and limit a site structure.
Amount of Thought Required
The key to understanding cognitive load is estimating how much a person needs to think about a decision prior to making it. Thought process is an abstract concept that varies from person to person and doesn’t necessarily correspond to time. This means that a longer experience could have a lower cognitive load than a shorter experience with a higher load. Don’t ask users to select between too many options. The ‘7, plus or minus 2’ is a tried and true rule of thumb for the number of navigation options, calls to action, categories or menu items to be displayed at any one time (though not applicable in every case, it is a good guideline to keep in mind).
Confusion and Choice
Not granting your users all appropriate options at a glance can lead to frustration or confusion. It’s a balancing act between too many choices vs leaving your user lost. In the case where an experience would suffer unless you display all options, it is possible to nest or arrange a subset of navigation options that are easily accessible again and again. This reduction of visibility does come at a cost, but is better than a limited or incomplete list of options.
Minimizing Cognitive Load
User attention is a limited and precious resource. As such, it should be carefully allocated. The strategies for achieving this include:
Content chunking is the strategy of breaking up content into shorter, bite sized pieces that are more manageable and easy to remember. It’s a great technique for content processing by accommodating working memory. By breaking down large amounts of text and multimedia content into smaller, distinct content units
Building on Existing Mental Models
People already have an existing idea of how websites work, based on their past experiences visiting other sites. When you use layouts and navigation that users are likely to have already encountered, you reduce the amount in learning involved in using your site.
Look for anything that requires users to read text, remember information or make decisions, then look for alternative methods of presenting information, be that redisplaying information, presenting it visually or recalling it in forms. Every mentally demanding task that you eliminate leaves more resources for more important decisions.
Avoiding Unnecessary Actions
Each step a user is presented with adds to their cognitive load. Too many unnecessary steps run the risk of overwhelming or irritating. Because the user’s working memory is already focused on accomplishing specific goals, unnecessary actions create friction, testing users’ patience. Pacing is an essential consideration for multistep tasks. Users want to accomplish their goals efficiently, so remove anything that might slow them down.
Cluttered or chaotic interfaces can confuse and distract a user from the task at hand, creating difficulty focusing. Too many images, animations, icons, ads, typefaces and colours fighting for your attention can be overwhelming. Working memory must sort through all that external stimulus in order to move forward, and every distraction demands a bit more of the user’s attention. Remove most or all inessential elements in order to streamline the experience.
Users like options, but paradoxically it overloads their brains. Hick’s Law – aka decision paralysis – tells us that the more options a user has, the more time they take to make decisions. Since this theory emerged in the 1950’s, it has been repeatedly confirmed by behavioral studies, most recently by a 2015 MRI study. Limiting options can improve UX by giving your user what they want and need in order to complete their task, as opposed to what they think they want.
The biggest culprit in cognitive overload is confusing user interfaces. The user should never have to spend long figuring out how to achieve a desired action they know is possible, or waste time deciphering icons. Don’t reinvent the wheel when it comes to your interfaces. Use visual cues or UI kits that your user is likely to already be familiar with. Users rely on common signifiers and affordances across the web and your site shouldn’t be any different. Certain cases will require never before seen interfaces, icons or custom solutions, but whenever possible, reference pre-existing conventions to avoid confusion.
Understanding cognitive processes and how they impact your user’s browsing and purchasing behavior can be instrumental to improving your site’s overall user experience. The Internet is a big and overwhelming place as it is and designers need to cater to their users’ needs any chance they get. So take Steve Krug’s advice and don’t make me think, or anyone else for that matter, unless we really have to.
References & Further Reading