Remembering Interaction Cost
A Framework for Cradle-to-Grave User-Centered Design
Summary: Interaction cost is a fundamental UX concept that's become overlooked in recent years. In this article, I attempt to reintroduce interaction cost and argue that considering it early will make sure your work stays holistically user-centered.
Interaction cost is a basic concept that us experienced UX professionals used to regularly talk about and consider in our daily work. (Yeah, I know I'm getting old. Whatever. Hahahaha) However, in recent years, I've noticed a huge decline in UXers' understanding of interaction cost. This knowledge gap seems to be more common among newer practitioners in the field. My goal with this article is to reintroduce the concept of interaction cost and use it as a gateway drug to encourage UXers to think more holistically about cradle-to-grave user-centered design.
My Definition: Interaction cost is the total effort people spend using anything they are interfacing with. Every interaction adds to the overall cost and unnecessary interactions stand out as really really bad.
Every extra click, unnecessary scroll, confusing button label, or unclear onboarding adds to this cost. In complex applications or multi-step workflows, interaction costs aren't trivial.
All those little usability errors add up fast and can severely impact productivity. High interaction costs aren't just annoying. They actively reduce users' efficiency, which inevitably affects our organization's bottom lines and drives users up the wall.
Why Interaction Cost Matters
Interaction cost directly affects how efficiently users complete their tasks and how satisfied they are with the software they use daily. Imagine a user dealing with software designed for managing compliance metrics. They need immediate access to important data but instead get confusing navigation, repetitive data entry, and unclear labels. Each unnecessary action adds extra time and effort to what should be simple.
When we don't identify and fix these design errors, it creates an environment where users are forced to repeat these faulty actions over and over again.
This drains our users quickly, and they can become jaded or even angry over time. Does this sound familiar at all to you? Do you ever want to throw your computer down a flight of stairs after a piece of software puts you through the wringer? I know I've been there before. Avoiding this is our job. We, as UXers, are obligated to ensure this doesn't happen to our users.
The impact isn't only time lost. High interaction costs also force users to pause continually, think through confusing steps, and correct avoidable mistakes. Users often resort to unofficial shortcuts or external tools to simplify their tasks. These shortcuts may initially seem helpful but typically introduce new inefficiencies, errors, or even security risks.
Decades of usability research support this view. According to the Nielsen Norman Group, interaction cost directly correlates with product usability. Also, many other academic studies have demonstrated that reducing interaction cost enhances user performance, reduces errors, and increases overall satisfaction. No, duh, right?
We've known these things to be true for 40-plus years now, so I say we start addressing it again.
How To Identify Interaction Cost
Because interaction cost is so important, I'm arguing that proactively identifying and addressing it should be foundational to our UX practice. This is where UX research comes in. By clearly pinpointing where users face unnecessary effort or confusion, research can guide design improvements. It's user-centered by definition, and its good for business.
Here are UX research methods that effectively identify interaction costs:
(Read the descriptions below and choose the method(s) that best fit your situation.)
1. Task Analysis and Time-on-Task Measurement
Task analysis means breaking down workflows into clear steps. Measuring each step gives you precise data about where users struggle most.
GOMS-KLM Analysis: This method estimates time on task by auditing every little thing a user has to do while performing a task. It'll help you pinpoint unnecessary steps and simplifies workflows.
PURE (Pragmatic Usability Rating by Experts): PURE evaluations use expert ratings of interface components based on ease of task completion. This will show you where interaction costs are highest.
Benchmark Usability Tests: Old-school timing with a stopwatch. Measuring task completion times and errors across multiple users helps identify common issues and clarifies exactly where your design improvements should focus.
Cognitive Walk-Throughs: Simulating a first-time user's journey quickly shows confusing elements or unclear interactions. Fixing these issues early prevents unnecessary intervention costs later on.
2. Contextual Inquiry and Ethnographic Research
Real-world complexity is never fully captured in a usability lab. Observational methods help you uncover interaction costs in users' actual environments.
Contextual Inquiry: Observing users performing real-world tasks in their real work environment reveals practical difficulties and hidden problems. These problems might not be obvious in controlled tests.
Shadowing and Longitudinal Studies: Following users over extended periods uncovers repetitive tasks, interruptions, and hidden inefficiencies.
3. Analytics and System Data Analysis
Interaction costs aren't just subjective. They can be measured objectively through analytics.
Workflow Drop-Off Rates: High drop-off rates may indicate where users encounter frustrating interactions. If you see this in your analytics data, consider looking into it further to identify the cause.
Error Logs and Undo Actions: Frequent errors or undo actions often show areas of confusion or poor design. If your analytics show this one as a specific interaction point or feature, consider conducting behavioral research as a follow-up.
Navigation Analytics and Session Replays: These methods highlight unnecessary scrolling, repeated actions, or inefficient paths through the software. Analytics data helps pinpoint exactly which interactions carry high costs. This can be used to help prioritize what fix will have the biggest impact for your users.
Integrating from the Start
I hope I've convinced you by now that proactively managing interaction costs is essential. Unfortunately, understanding and reducing interaction cost early in the design process has become increasingly uncommon. Many UX teams now wait until issues arise from user feedback or support tickets.
A better strategy is integrating interaction cost reduction into your research and design practices from the very beginning.
In my experience, proactive management of interaction costs is the only way to use this information as a framework for change. Here are some tips for doing that in the real world:
Early Prototyping and Usability Testing: Early prototyping allows UX researchers and designers to quickly identify and fix usability issues. By testing key workflows before extensive development, teams can avoid costly redesigns and improve overall user experience from the outset.
Task-Focused Roadmapping: Including interaction cost reduction explicitly in your product roadmap ensures consistent focus throughout the project's lifecycle. It aligns stakeholders around common usability goals and prevents interaction issues from becoming overlooked or deprioritized.
Cross-Functional Collaboration: Collaboration between UX researchers, product managers, engineers, and designers ensures that reducing interaction costs is a shared goal. Regular communication and alignment on usability findings help create a more streamlined, user-focused development process, resulting in better-designed products.
Proactively identifying interaction costs through structured UX research ensures your team builds software that supports user efficiency rather than hinders it.
Conclusion
Interaction cost might seem like a small consideration, but its impact on user efficiency and satisfaction is profound. By re-focusing on this UX principle, teams can transform complex interfaces into intuitive tools that enhance productivity and overall user experience.
Simply put, reducing interaction costs improves software, reduces errors, and minimizes user frustration.
By consciously integrating methods to identify and reduce these costs from the start, UXers can create better designs day one. Ultimately, prioritizing interaction cost reduction is not only beneficial for users but also delivers measurable benefits to organizations in terms of productivity, engagement, and long-term success.
How do you think about interaction cost? Are there any tips, tricks, strategies, or methods I missed? If so, please comment or DM me with your thoughts. Thanks, everyone!