How Human Memory Works

Short-term memory, also known as active memory, is the part of our memory where we jot down quick notes that we need to keep handy for just a short while. We use it for everyday tasks, such as keeping a phone number in mind until we dial it. If we don't actively review or repeat this information, it tends to fade quickly. Typically, short-term memory can hold information for about 20-30 seconds, and according to psychologist George Miller, it can store around 7 items, plus or minus two.^[1]

Working memory is a bit like a mental workspace that allows us to hold and manipulate information temporarily. Think of it as the brain's sticky notes, where we jot down and shuffle information needed for tasks we’re currently doing, like solving a math problem in our heads or planning what to say next in a conversation. It’s more complex than short-term memory because it doesn’t just store information — it actively works with it.

If a task has a high cognitive load, it means it's putting a lot of pressure on working memory, making tasks seem difficult. Since everyone's working memory capacity can differ based on factors like education, IQ, and age, it varies widely among individuals. However, interfaces should be designed in a way that doesn’t overload users' working memory, irrespective of individual capacities.^[2]

External memory refers to tools or aids that help us store and access information outside our own brain. Think of it like using a notepad to keep track of information you don't want to forget. This kind of memory allows us to save mental energy for other tasks and reduces the load on our working memory.

In the context of UX design, external memory might be any feature in a user interface that lets users save and retrieve information necessary for their tasks. For example, a comparison table on a shopping website acts as external memory. It helps users review different products side by side, keeping important details visible so they don’t have to remember everything about every item.

Spatial memory is our ability to remember where things are located in our environment. It works by creating mental maps of spaces we're familiar with, like our homes or favorite stores. When we navigate these spaces, our brains use landmarks and patterns to recall where things are.

In UX design, spatial memory is important because it helps users find their way around interfaces. You can enhance user experience by organizing information logically and consistently, making it easier for users to remember where to find things. For example, placing important features like a navigation menu in a predictable location like the top or left side of a website or app can leverage users’ spatial memory to improve usability.

Recognition and recall are two ways we retrieve information from memory. Recognition involves identifying information when it is presented to us. For example, recognizing a friend's face in a crowd. Recall, on the other hand, requires us to retrieve information from memory without as many cues. For example, remembering a friend's phone number without looking at it.

In UX design, recognition is utilized by providing users with familiar cues or prompts, such as icons or labels, to help them easily identify and interact with interface elements. Recall is engaged when users must remember specific information, like login credentials, without any visual cues. Balancing both types of memory retrieval ensures a user-friendly experience by accommodating different levels of cognitive effort.

Reminding users of previously visited content is a great way to promote recognition and recall. Here are some ways to do so:

• Provide a history feature that allows users to recall recently visited pages. This can help them continue incomplete tasks that they have difficulty recalling.
• Implement “Recently Viewed” sections or personalized recommendations based on past interactions to remind users of content they've engaged with previously.
• Provide features like favorites, wish lists, and shopping lists that allow users to save information and easily access it when needed. These features promote recognition and eliminate the need for users to remember every piece of interesting content they come across or like.^[3]

To ensure your interface is user-friendly, avoid overwhelming users' memory, make recognition and recall easier by providing:

• Contextual help: Use tooltips to offer on-the-spot assistance, when users hover over a feature. For example, during checkout, a tooltip next to the CVV field can clarify what CVV is and where to find it on their credit card. Ensure tooltips are concise and relevant, offering clear instructions without cluttering the interface.
• Accessible tutorials: For complex tasks like returning or replacing a purchased item, offer tutorials that can be accessed at any time. These tutorials should be easy to find and navigate, providing clear instructions and visuals to guide users. For instance, a "Help" section with video tutorials or step-by-step guides can assist users in learning without feeling overwhelmed.

Progressive disclosure is a design strategy that shows users only the essential information first, and reveals more details as needed. This prevents users from feeling overwhelmed by too much information at once, especially in complex interfaces.

You can use progressive disclosure in various settings like:

• Menus: Start with basic menu options and reveal more as users dig deeper.
• Onboarding flows: Show the most basic or important features one at a time and reveal more as users progress through the flow.
• Tutorials and help guides: Give simple overviews initially, then provide detailed steps when users click for more info.
• Forms and surveys: Show initial questions and display additional fields based on previous answers.

Progressive disclosure helps manage user interactions smoothly, making complex systems user-friendly and less daunting.

Gestural interfaces, like those on smartphones and touchscreens, rely on users recalling specific hand movements to interact with the device. Since these gestures aren't always obvious, make use of gestural signifiers — visual cues that help users remember what to do. These cues guide the user, making interaction smoother and more intuitive. For example, in a touchscreen navigation app, an animated hand icon could demonstrate pinching to zoom in on the map.

Best practices for using gestural signifiers include:

• Keep gestures and their signifiers consistent across the interface to strengthen memory.
• Make sure signifiers are clearly visible where gestures are needed.
• Use simple and natural gestures that align with common human actions.

Adaptive interfaces change based on user behavior, which can be confusing because the interface might look different each time. This constant change forces users to remember new layouts and options regularly, which can be overwhelming and make the UI harder to use. Instead of adapting too aggressively, it's better to keep a consistent layout where users know where to find things. For instance, if a menu constantly shifts its items based on what you click most often, you might struggle to find less frequently used options when you need them. Keeping a stable menu layout where everything remains in a predictable place helps users build spatial memory, making for a smoother, more enjoyable user experience.

However, adaptive interfaces can be particularly effective in interfaces where spatial memory isn't as crucial. Take an e-commerce website for example, it could display personalized product recommendations based on users' browsing history or past purchases. So while consistency can be user-friendly, there are scenarios where adaptiveness can enhance the user experience.

When users try to find something in an app or on a website, they often remember only the general area where it might be, not the exact spot. This can make finding specific things a bit like hunting for a lost sock in a messy room — we know it’s around, but we need to look around to find it.

To make this easier, add extra clues in the form of:

• Icon labels: For example, in a music app, a heart icon might be unclear on its own. Adding a label that says "Favorite" clarifies that tapping the icon will save the song to users’ favorites list.
• Thumbnails for documents: When looking through a long document, small preview images of each page can help users jump right to the page they need without flipping through each one.
• Colors and badges: Highlighting important or different items on dense lists with a different color or a badge makes them stand out. For example, important emails could have a red dot next to them within an email app interface.

A broad and shallow hierarchy organizes information or options across a few layers that are easily visible and accessible. This contrasts with a narrow and deep hierarchy, where information is stacked under several layers, requiring more navigation steps to access. For example, consider a mobile app for a news site. A broad and shallow hierarchy might have a main screen with large, clear buttons for categories like "World News," "Sports," "Entertainment," and "Weather." Tapping on one of these buttons might bring you directly to a list of articles in that category. This setup allows users to access the information they need quickly and with minimal effort.

This helps users find what they need faster without memorizing complex navigation paths or making many clicks. It makes the interface easier to use and enhances the overall user experience by reducing cognitive load and navigation time.^[4]

However, in some situations, there may simply be too many categories to show them all at one level. In other cases, showing specific topics too soon will just confuse your audience, and users will understand your offerings much better if you include some intermediate category pages to establish context.

Use landmarks to help users navigate smoothly and quickly within a UI. These are consistent, recognizable features that remind users where they are and how to get where they want to go, reducing the need to remember complex paths.

Examples of digital landmarks include:

• Clickable logos at the top of each page that, when clicked, always take you back to the homepage.
• Browser tab titles that let you know what page you’re on, making it easy to switch between tasks without losing your place.
• Breadcrumb trails on websites that show you the path you’ve taken from the homepage to your current location. This lets you backtrack easily without hitting the Back button repeatedly.
• Visual changes such as different colors or layouts in different sections that help you recognize each area quickly.^[5]