A user should be able to start a task to process, stop in the middle, and come back to it later. They should be able to pick up right where they left off without losing their place or having to re-enter any information.

The Reentrance Property

When people change their mind about what they want to do, in the middle of doing something. They start out planing to do one thing, but then, whether on purpose or by accident, end up doing something different. This means you should design for this and allow users to change their mind frequently, abiding by the usability guideline of "user freedom and control."  You should also support a property called "reentrance."

University of Michigan - Ann Arbor

This touches on some of the most common ways people think and behave as it relates to software interfaces. Individuals are unique, but people generally behave predictably according to cognitive science.

- Safe Exploration
- Instant Gratification
- Satisficing
- Changes in Midstream
- Deferred Choices
- Incremental Construction
- Habituation
- Microbreaks
- Spatial Memory
- Prospective Memory
- Streamlined Repetition
- Keyboard Only
- Social Media, Social Proof, and Collaboration

Patterns of Cognition and Behavior Related to Interface Design

Designing Interfaces, 3rd Edition
by Aynne Valencia; Charles Brewer; Jenifer Tidwell
Published by O'Reilly Media, Inc., 2020

Designing Interfaces, 3rd Edition

When a user feels like they can explore something without becoming lost or getting into trouble. Good software allows people to try something unfamiliar and back out when they choose, all without annoyance, stress or consequences. This pattern is related to a few Nielsen Norman usability guidelines including: "visibility of system status," "match between the system and the real world," and "user control and freedom."

Safe Exploration

People are more likely to keep using a site if they have a "success experience" within the the first few seconds of using the site, even if it becomes more difficult to use later on. This early "success experience builds confidence in themselves and in the system they're using. Creating an experience like this requires identifying and anticipating the users' needs and making those goals easy for them to accomplish right away.

Instant Gratification

This term comes from a combination of the words satisfying and sufficing. It was created in 1957 by the social scientist Herbert Simon. It refers to the idea that people are willing to accept something that is "good enough" if it saves time and effort. People don't typically look at every single option they have, analyze it, then pick the best one. Instead they try to save time by scanning their list of options quickly, and then picking the first one they think might work. This behavior is also related to the idea that there is a tradeoff between time spent collecting information and time spent making decisions. Designers should try to reduce visual complexity whenever possible in order to mitigate the cognitive cost on users and, in turn, their need to "satisfice."

Satisficing

Changes in Midstream

The tendency of task-focused users to want to complete their goal before having to do something else. This means they would like to defer certain tasks for the time being while they complete their current one.

This stems from people's desire for instant gratification. See design implications of this pattern.

Deferred Choices

People don't often create something perfectly and completely the first time. Implication: Make it easy for users to build in small pieces and allow for the user to go through various iterations of a task. Additionally, try to show the effects of any user changes with as little delay as possible (give good response and feedback). Relates to the usability guidelines of user control and freedom, as well as visibility of system status.
- Depending on how supportive the tools are for creative and iterative work, they can allow the user to experience a flow state. "This is a state of full absorption in the activity, during which time distorts, other distractions fall away, and the person can remain engaged for hours—the enjoyment of the activity is its own reward. Artists, athletes, and programmers all know this state."

Incremental Construction

The tendency for users to make habits out of common and repeated actions to the point where they no longer need to think consciously about doing them. For example, pressing ctrl-S to save something. This can be leveraged in design to improve efficiency and make a system easier to learn to use. However, it also means that the user might wrongly assume something will work a certain way in accordance with what they're used to doing. This is why it's important to verify the gestures in your design all do expected things.  

Habituation

The tendency for people to want to fill small windows of downtime with something constructive or entertaining. In this case, users do not have enough time to become deeply involved in an activity. This pattern especially applies to mobile devices because people can easily pull them out during these "microbreaks." Social media and casual gaming take advantage of this pattern extremely well. 

The implications of this in design are to support entrance and re-entrance. This means you should make an activity easy and fast to reach without a complicated set up or long loading times. Load the freshest content the quickest, restore the application to the previous state the user left it, and try to keep a user logged in as much as possible. Additionally, when showing a list of items try to display enough data per item that the user can identify what to do with it without opening each item individually.

Microbreaks

People often use their spatial memory to locate elements they've previously interacted with, rather than remembering what that element was called. They might do this by recalling where something was located on the screen, or recalling where it was relative to the other things around it. Once they get used to a certain spatial layout, their navigation through it becomes similar to habituation.

One thing to note is that people are more likely to remember where things are when they place it themselves. Additionally, the primacy and recency effect occurs with menus, where people cognitively tend to remember the first and last things in a list better than the things in the middle.

Spatial Memory

Also referred to as "prospective remembering," this pattern is a product of imperfect human memory where people use various artifacts or memory aids to remind themselves of things they need to do in order to be successful in their complicated, highly scheduled lives. For example, leaving an unsent email on the screen so you remember to send it later, or setting an alarm 5 minutes before a meeting.

Examples of memory aids people can use are:
- notes to oneself, virtual "sticky notes"
- windows left on-screen
- annotations put directly into documents
- document stored on desktop rather than somewhere else in the filesystem
- unread emails in inbox, maybe flagged, instead of filed away

Prospective Memory

Make repetitive actions as easy and efficient as possible. Offer users a way to streamline repetitive tasks that could otherwise be time consuming, tedious, and/or error prone. Direct observation of users can help you determine what kinds of repetitive tasks you need to support, since users con't always tell you. 

Examples:
- copy/paste
- find and replace

Streamlined Repetition

Some people have physical trouble using a mouse, others prefer not to switch between mouse and keyboard, and still others can't see the screen so they use assistive technology to interact with the system using they keyboard API. Keyboard-only usage is particularly important for data-entry applications where the speed of data entry is critical.

Design Implication: Don't shut out keyboard-only users of any functionality. 
- Define keyboard shortcuts, accelerators and mnemonics for operations reachable via application menu bars.
- Allow keyboard selection from lists, even multiple selection with key combinations
- Support *tab traversal*
- Allow users to change their values from the keyboard using arrow keys, the return key, or the space bar
- Support a default button to signify when a user is done with a task


Keyboard Only

The natural human tendency to be influenced, whether directly or indirectly, by other people's choices. People are much more likely to do something if we see someone we know has done that thing as well. This is called *social proof* and it motivates people to take action. Social group identity, participation, and recognition are powerfully rewarding to people.

Design Implication: Enabling social dynamics in your software can bring increased engagement, virality, community, reward, and growth.

Examples:
- user-generated reviews and comments (reviewers can be rated and participants can gain rewards for being a good reviewer)
- everything is a social object that people can virtually gather around (anything can be shared, rated, have a discussion thread attached to it, etc.)
- collaboration, whether virtual, live, or asynchronous
- help systems (an online support community is a valuable part of a complete help system)

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