Summary: Getting to the bottom of your desirability criteria is more important than understanding usability. Since usability metrics are based on successful task completion, they come second after first clearly representing user tasks, needs, and goals. Desirability criteria should be defined first, then usability considered and tested next. Understanding desirability and what users truly want and need can differentiate a design, product, or value proposition fundamentally, with impacts on business results like conversion, engagement, and user adoption.
First, what is desirability?
Desirability represents the other side of the "two sides of UX". The first side, Usability, gets more attention in User Research, but it is a reactive approach--usability is investigated usually after a product is complete. Usability is about fixing things that are broken, by evaluating and testing. Desirability defines the problem to be solved, from a customer's perspective/ journey. Usability and other forms of conversion optimization like A/B testing are essential, however, if you optimize something that may have assumptions of user tasks, you may miss this more strategic understanding of UX-- desirability. Good UX means the user can use it easily but also means they want or desire to use it in the first place.
Desirability asks first: 'What are the user's actual tasks?'; Once that has been clearly defined and designed with user observations and interviews, then we can worry about testing and improving the usability of the user interface (UI). - Frank Spillers, Experience Dynamics
Important Clarification: The term "Desirability" is often used in the UX community to test branding and Visual Appeal. Microsoft's Desirability Toolkit offers a way to do this. However, this is not how we use the term at Experience Dynamics. Like many UX professionals, we choose to break with this definition of desirability because the term itself is better used to describe the problem of meeting user needs. Simply describing user needs as "tasks, requirements, context, or jobs" we have found resonates less with stakeholders (they assume that usability is covering that). Describing 'Desirability criteria' reminds us that user desires (wants and needs) have an emotional component that exists at a different level of UX. Usability focuses on logical outcomes: eg. Does it work as expected? Desirability introduces questions such as: eg What are user expectations?
So, there is no question that desirability is more important than usability when designing UX or building, optimizing, and redesigning products or services.
When Desirability Matters in UX
Ideally, desirability related questions should be answered up-front in a design or re-design process. If you are conducting Design Sprints (a workshop method for designing and user testing in one week), bringing field research to your first-day Design Sprint will improve your ROI, we have found.
Back-tracking to figure out desirability can be done with finished products or services. However, due to the strategic insight gained from surfacing desirability criteria, you may be left with an extensive Agile Backlog, a clearer MVP, or a completely new way of laying out or positioning your core UI, value proposition or UX strategy. We think these are good problems to have, but be aware they are strategic "fixes" not quick and easy "features" that can be bolted on.
How to gather Desirability criteria
Desirability is gathered by "Day in the Life" interviews and observations. This can involve techniques from Ethnography ("culture study"), Contextual Inquiry (a technique that focuses on context of use) or Task Analysis (a 40-year old technique for mapping user tasks to features).
Desirability is at the heart of UX and Service Design tools commonly used in teams today: Personas and Customer Journey Maps. Persona quality can be severely compromised without desirability criteria (see: Your Personas are Garbage without good User Research). Likewise, running Journey Maps that are not based on user research and desirability criteria are dangerous to design decision-making.
Desirability studies often involve 15-30 users (5-10 per segment), with the goal of identifying patterns, pain points, undiscovered needs, workflow and taskflow as well as goals, tasks, and sub-tasks. At Experience Dynamics, we also capture emotional and social requirements. For example, in a doctor's office study we found stacks of iPads, un-used. The reason was that these devices are not multi-user and Doctors did not want others, eg Office Staff to access confidential patient data. A different study involving billing administrators in healthcare departments found stacks of paper print-outs, highly desired in order to "track and work a job queue"-- without proper functionality for tracking and managing billing issues, printed paper was more highly desired than digitized reports--- making the product team's honorable "save a tree" goal of digitized invoices, an invalidated assumption, or one lacking the necessary steering based on the user's context of use and desirability criteria.
Conclusion: Desirability is at the heart of good UX. Most vulnerable to miss this distinction are smaller firms, non-profits, Independent Software Vendors and even medium to large (Enterprise) organizations, which tend to unevenly scale UX excellence. Emerging Markets are also slow to understand this important UX process: eg In India managers see UX as analytical, possibly allowing user testing and nothing more. In China, managers value quick ROI-yielding features and functionality over exploring user expectations and needs. In the US, these same problems occur in organizations big and small, as UX is seen as a creative or analytical art and not cognitive, behavioral, or anthropological science. Simply, product managers tend to follow the culture of Quant-itative decision-making ("Show me some numbers!") over insight-driven intuitive decision-making or Qual-itative evidence ("Why are customer finding this task awkward?").
Understand desirability and what users truly want and need can differentiate a design, product, or value proposition in a fundamental way with very real impacts on business results like conversion, engagement, and user adoption. See this case study of a UX redesign of a bank call center, where desirability improved success rates from 55% to 92% after the redesign.
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