Interaction design is an important component that falls under the huge umbrella of user experience (UX) design. This article will look at what exactly interaction design is, some useful interaction design models, as well as a brief overview of what interaction designers do.

What is interaction design?

Simply put, interaction design refers to the process of designing interactions between products and their users. When talking about interaction design, people most often refer to interactions between people and software products such as websites or mobile apps. Interaction design aims to build products which allow users to successfully complete their goals in the best way possible.

This definition is rather broad because the field itself is also broad; interactions between users and products typically involve elements such as aesthetics, sound, space, motion, and more. Additionally, each element can also involve more specialized fields such as sound design for creating the sounds that will be used in user interactions.

You may have already realized that there is a significant overlap between UX design and interaction design. After all, UX design is heavily focused on improving the experience of using a product, and most of the experience with a product involves interactions between it and the user. Keep in mind, however, that UX design goes way beyond interaction design: it also involves user research, crafting user personas, conducting user testing, usability testing, and so on.

The 5 dimensions of interaction design

Kevin Silver described a model of interaction design which involves five dimensions. Gillian Crampton Smith, an interaction design academic, initially introduced the concept of an interaction design language with four dimensions, to which Silver added a fifth.

First dimension: Words

Words, particularly those used in interactions such as button labels, should always be meaningful and easy to understand. Everything you write throughout your product should communicate information to users but be careful not to include too much information as it may overwhelm them.

Second dimension: Visual representations

The second dimension concerns graphical elements such as images, icons, and even typography which users interact with. These visual elements supplement the copy used to communicate information to your users.

Third dimension: Physical objects or space

What physical objects do people use to interact with your product? Is it a laptop or PC with a mouse or touchpad? Is it a smartphone with a touchscreen? And within what physical space does the user perform these interactions? For example, are they in a crowded space when using the app on their phone, or are they sitting at a desk browsing your website?

These and many more are factors which influence the interaction between users and products.

Fourth dimension: Time

This may sound a bit abstract, but it mostly refers to any type of media which changes with time, such as videos, sounds, or animations. Media plays an important role in giving users’ interactions visual and audio feedback.

This dimension also refers to how much time users spend interacting with a product: can they track their progress or resume their tasks at a later time?

Fifth dimension: Behavior

This refers to the mechanics of a product: how do users perform actions in the app? How do they operate the product? Simply put, it’s how all the previous dimensions define the interactions a user has with the product. It also includes their reactions, such as emotional responses, or feedback from the product.

Key questions that interaction designers ask

To get a better understanding of how interaction designers work with the five dimensions mentioned earlier, we can look at some important questions that they ask when they are designing something for users, as found on usability.gov.

Define how users can interact with the interface:

• What can a user do with their mouse, finger, or stylus to directly interact with the interface? This includes pushing buttons, dragging and dropping across the interface, etc.
• What commands can a user give, that aren’t directly a part of the product, to interact with it? An example of an “indirect manipulation” is when a user hits “Ctrl+C”, they expect to be able to copy a piece of content.

Give users clues about behavior before actions are taken:

• What about the appearance (color, shape, size, etc) gives the user a clue about how it may function? These help the user understand how it can be used.
• What information do you provide to let a user know what will happen before they perform an action? These tell users what will happen if they decide to move forward with their action. This can include meaningful label on a button, instructions before a final submission, etc.

Anticipate and mitigate errors:

• Are there constraints put in place to help prevent errors? The Poka-Yoke Principle says that placing these constraints forces the user to adjust behavior in order to move forward with their intended action.
• Do error messages provide a way for the user to correct the problem or explain why the error occurred? Helpful error messages provide solutions and context.

Consider system feedback and response time:

• What feedback does a user get once an action is performed? When a user engages and performs an action, the system needs to respond to acknowledge the action and to let the user know what it is doing.
• How long between an action and a product’s response time? Responsiveness (latency) can be characterized at four levels: immediate (less than 0.1 second), stammer (0.1-1 second), interruption (1-10 seconds), and disruption (more than 10 seconds).

Strategically think about each element:

• Are the interface elements a reasonable size to interact with? Fitts’ Law says that elements, such as buttons, need to be big enough for a user to be able to click it. This is particularly important in a mobile context that likely includes a touch component.
• Are edges and corners strategically being used to locate interactive elements like menus? Fitts’ Law also states that since the edge provides a boundary that the mouse or finger cannot go beyond, it tends to be a good location for menus and buttons.
• Are you following standards? Users have an understanding of how interface elements are supposed to function. You should only depart from the standards if a new way improves upon the old.

Simplify for learnability:

• Is information chunked into seven (plus or minus two) items at a time? George Miller found that people are only able to keep five to nine items in the short-term memory before they forgot or had errors.
• Is the user’s end simplified as much as possible? Tesler’s Law of Conservation notes that you need to try to remove complexity as much as possible from the user and instead build the system to take it into account. With that said, he also notes to keep in mind that things can only be simplified to a certain point before they no longer function.
• Are familiar formats used? Hick’s Law states that decision time is affected by how familiar a format is for a user to follow, how familiar they are with the choices, and the number of choices they need to decide between.

Principles of interaction design

There are many interaction design principles, way too many to mention here, but let’s look at some general areas widely used in this field:

Goal-driven design

This is a design style which mainly prioritizes problem-solving. It is focused on satisfying the user’s specific wants and needs, which is the overall goal of interaction design.

Good usability

Usability refers to how well people can use a product, and great usability is a key requirement for interaction design. Usability is directly impacted by four things:

1. learnability – how easily users can learn to use an interface
2. efficiency – how quickly users can perform tasks
3. error rate – the number of errors users make during an interaction
4. error recovery – how quickly users can recover from errors

Usability can be measured using task-completion time as well as overall satisfaction – how much users enjoy using your product.

When making design decisions, interaction designers typically familiarize themselves with the users’ mental model, which describes the way a person perceives the product they are using. Using these mental models, they can create intuitive UX design systems.

Ergonomics

Interaction designers also need to apply certain physiological principles when designing products. The aim is to reduce human error, enhance the interaction’s safety, and increase productivity.

Interaction designers typically use a predictive model of human movement called Fitt’s law when designing interactions. This law states that the time needed to quickly move to a target area is a function of the ration between the distance to that target and the target’s width. It is used to model the act of pointing and can be applied when a UI element is interacted with either by using a pointing device such as a mouse or with a hand or finger on a touchscreen.

Positive emotional responses

Designers must always craft designs which positively influence users’ emotions. Interaction designers are aware of elements which influence users’ emotional responses such as fonts, animations, colors, and more.

Always design for people

When designing a product, designing for an abstract user is difficult. Designers should always evaluate their decisions within the context of a specific user group, and personas are great tools which can help with this.

Personas encapsulate key data about user groups in ways that designers can easily understand and relate to. The emotional aspects of personas help designers build better product behavior.

Design patterns

Designers use patterns to address interaction problems. Patterns are solutions for particular contexts and designers can often address new issues by modifying existing patterns. Interaction design aims to create solutions which fit well in the context of use.

Interaction designers typically start with well-known interface guidelines such as Google’s Material Design or Apple’s Human Interface Guidelines. These guidelines provide patterns which are familiar to users and also explain how they should be used in various contexts.

Design iterations

Designers can have more than one solution for a particular interaction issue. The only correct way of reducing the number of design options is by testing and seeing how they work for real users. Not all assumptions pass testing and often enough designers need to design alternative solutions. This is why interaction design is typically an iterative process instead of a linear one.

What do interaction designers do?

An interaction designer’s job isn’t as clear cut as you might think and depends on their company and the project they are working on.

For example, if the company they are working in is large and has a lot of resources, it may have separate jobs for interaction designers and UX designers. A large design team could have an interaction designer, a visual designer, a UX researcher, and an information architect, for example. Smaller companies and teams, on the other hand, may put the weight of the UX design job on just one or two people who may or may not have the title of interaction designer.

An interaction designer’s responsibilities generally include identifying a product’s key interactions and building prototypes to test concepts. Let’s go ahead and look at two areas where an interaction designer’s impact if particularly significant:

Design strategy

This concerns user goals and what interactions are necessary for them to achieve those goals. Depending on their company, interaction designers may also need to conduct user research to know exactly what users’ goals are before they can develop a strategy which translates that into interactions.

Wireframes and prototypes

This also depends on the company and the job description, but most interaction designers are required to build wireframes which showcase the layout of interactions within the product. They are also sometimes required to create interactive prototypes or high-fidelity prototypes which need to look just like the finished product would.

Interaction designers work with other designers such as UX and visual designers to ensure that products correctly implement every interaction pattern.

Takeaways

Digital design is a conversation which happens between a person and the machine they are interacting with. When people are interacting with a product, smooth and simple interactions are expected, but they only occur when interaction designers have made sure of it.

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