The dangers of assumption-driven design

Nigel Moyes

No matter your role within an organisation, it's easy to fall into the trap of making assumptions and letting them guide your decision-making.

After all, we're experts at understanding the work we do and what our customers need, right? Unfortunately, these assumptions can lead to significant pitfalls when designing and building digital products and services, and what we deliver to the communities we serve. At best, assumptions may waste your team or your audience’s time. At worst, they may lead to real and lasting harm. So, what are the dangers of assumption-driven design and how can we best identify and work past them, towards empathic and data-driven design?

What is an assumption?

Assumptions are subconscious beliefs, ideas, or conclusions that we take for granted as true, often without concrete evidence or validation. In the context of design and innovation, assumptions can pertain to user behaviours, preferences, or expectations. They’re the unspoken, untested hypotheses that underlie decisions. Assumptions can be about how users will interact with a digital product, what features they will find useful, or even the problems they need solving.

These assumptions shape the entire design process, influencing everything from the initial concept to the final product. While some assumptions may prove to be accurate, many others can lead to costly missteps and a suboptimal and potentially harmful user experience.

Assumptions often arise from a combination of factors:

Previous experience

Relying on past experiences and knowledge of user behaviour, which can sometimes lead to overconfidence and complacency. What worked in one context may not apply universally.

Implicit biases

Unconscious biases—associations you might hold without even being aware—can lead to assumptions about the needs and preferences of users. These biases may be based on age, gender, cultural background, or other factors, potentially excluding diverse perspectives.

Stakeholder influence

Sometimes, stakeholders or decision-makers within a project can introduce their assumptions and preferences, which may not necessarily align with the end-users' needs or expectations. Due to the authority (real or perceived) within an organisation, these assumptions can often be taken as fact when there may be no data to support it. Always (respectfully) interrogate the HiPPO (‘highest paid person’s opinion').

Time and resource constraints

In fast-paced development environments, there may be limited time and resources available for comprehensive user research. As a result, designers may lean on assumptions to expedite decision-making.

Lack of user feedback

Without regular access to real user feedback, designers may fill the gap with assumptions, trying to anticipate what users want or need.

Assumptions may be sneaky, but their impact on your business can be huge

Assumptions are often the silent saboteurs of design. They may stem from well-intentioned hunches and prior knowledge, but can steer your project off-course. Here's why assumptions can be dangerous to your organisation:

Misaligned products and services

One of the fundamental principles of design is empathy for the end-user. Assumptions can create a gap between what you think users want and what they actually need, disconnecting your product from its intended audience. This misalignment can result in poor user engagement, as people find it challenging to interact with the product effectively, or not worth their time in the first place.

Wasted resources

Building features or functionalities based on unverified assumptions can lead to wasted time, effort, and resources. It's like painting a picture without knowing what the final image should look like.

Missed opportunities

Assumptions can prevent you from identifying new opportunities or innovative solutions. By sticking to what you think you know, you might miss out on groundbreaking ideas that could set your product apart.

Lost Revenue

An unsuccessful product means lost revenue opportunities. Assumptions can lead to features or elements that are overlooked by users or, even worse, deter them from making purchases.

Negative Brand Perception

A product that doesn't meet user expectations can harm your brand's reputation. Users who encounter frustration or disappointment are more likely to associate those feelings with your brand as a whole.

Beyond business impacts, real and lasting personal harm is possible

The dangers of assumption-driven design can also, unfortunately, get much worse. Beyond leading your organisation to potential failure, letting your assumptions guide your decision-making can actually lead to causing real, lasting harm to the people you’re trying to serve.

Physical safety risks

In certain contexts, such as healthcare, aviation, or automotive design, incorrect assumptions can have severe physical safety implications. Assumptions about user behaviour or system reliability can lead to accidents, injuries, or even loss of life. The consequences of design assumptions in safety-critical industries can be catastrophic.

Financial impacts

In financial and e-commerce applications, design assumptions can lead to significant financial losses for users. For example, if designers at a stock trading platform assume their users are generally well-versed in financial markets, they may cause inexperienced investors to make mistakes that lead to significant financial loss. Assumptions can also lead to financial fraud if security measures are inadequate.

Legal and compliance issues

Assumptions that lead to non-compliance with legal regulations, data privacy laws, or industry standards can expose users to legal risks. User data may be mishandled, leading to privacy breaches and potential legal actions against both the designer and the user.

Health and wellbeing impacts

In healthcare and wellness apps, design assumptions can impact a user's health and wellbeing. Assumptions about how users will engage with a health monitoring app, for instance, could result in missed or inaccurate health data, leading to suboptimal medical decisions and health risks.

Emotional impacts

Assumptions that result in a negative emotional impact on users can be especially significant. Poor design choices based on assumptions can cause stress, anxiety, and frustration, which can lead to long-term emotional harm and a negative perception of the product and brand.

Take YouTube’s introduction of 'Restricted Mode' in 2017 for example. In an attempt to address a serious and growing content moderation problem on the platform, Restricted Mode aimed to filter out potentially mature or sensitive content. However, this feature often blocked LGBTIQA+ content, causing emotional distress among content creators and users. They saw this as a form of censorship and discrimination against LGBTIQA+ voices. YouTube faced intense backlash and had to address the issue to mitigate emotional harm.

While it is difficult in this instance to determine whether these impacts were the direct result of assumptions, nefarious intent, or poor implementation—it still goes to show how the well-intentioned introduction of a new design feature designed to prevent harm and increase safety can actually cause harm if not properly and thoroughly considered.

Accessibility and inclusion

When designers assume that a product's user base consists of a homogeneous group, they may inadvertently exclude diverse user populations, such as individuals with disabilities, the elderly, or those from different cultural backgrounds. This exclusion not only harms these users but also represents a missed opportunity for market expansion.

Now that we know how seriously astray our assumptions can lead us, and the irreparable harm they can cause, what can we do about them?

Identifying assumptions

Before you can challenge and validate assumptions, you must first identify them. Here are some strategies to uncover assumptions in your design process:

Bring your assumptions into the light

Whether you work alone or with a team, spend some time teasing all of your assumptions out of your heads and onto paper. You can easily identify assumptions by prompting yourself with pointed questions like ‘Our users are…’, ‘Our users need help with problems such as…’, ‘We can solve these problems by…’. Once you’ve answered these and any other questions you can think of, interrogate your answers. What has led you to answer in the way that you have? What concrete data or evidence do you have to back up any of your answers? Which of your answers seem the most risky if incorrect? By the end of this activity, you should be able to identify the assumptions that are most likely to lead you astray or which require data to validate or reject. Do this regularly throughout all stages of a design project.

Document Everything

Keep detailed records of design decisions and rationale. This will help you identify where you might have made assumptions based on previous knowledge or experiences.

Engage your audience directly

Regularly engage in user research, surveys, and usability testing to gain real insights into your users' behaviours and preferences. Not only will this help you avoid being guided by your assumptions, it can actually help you identify assumptions you didn’t even know you had.

Stakeholder Input

Consult with your team and wider stakeholders. They may have their assumptions and preconceptions about the project. Open and honest communication can help bring these assumptions to the surface.

Challenging and validating assumptions

Once you've identified assumptions, it's time to challenge, reject, or validate them. You can do this in a number of ways, but all of them involve engaging with real users in one way or another. Some of the most common approaches to validating and/or challenging your assumptions include:


Interviewing users is a vital technique for challenging and validating assumptions. It provides rich insights into user needs, confirms or refutes design assumptions, supports iterative design, builds empathy, reduces biases, uncovers unarticulated needs, and validates priorities. This direct connection with users helps ensure that design decisions are grounded in reality, leading to more user-centred and successful digital products.

Prototyping and usability testing

Involve real users in the design process through usability testing. Create low-fidelity prototypes to test assumptions before investing significant resources. Prototyping allows you to make quick adjustments based on user feedback, reducing the risk of building on unfounded assumptions. Testing your prototypes will provide invaluable feedback that can either confirm or challenge your assumptions.

Data-driven design

Incorporate analytics tools to gather user data. This will provide concrete evidence of how users interact with your product and help in making informed design decisions.


In the world of design and innovation, assumptions can take you into treacherous waters. The dangers of assumptions can range from poor business performance, to causing severe and irreparable harm to your audience. To mitigate these risks, it's essential to identify, challenge, and validate assumptions at every stage of the design and innovation process.

The benefits are clear: improved alignment with your audience’s needs will typically lead to happier customers and greater business success. So, the next time you find yourself speeding through a project or initiative without consulting the very people you are aiming to help, take a step back, question your assumptions, then challenge or validate them through direct engagement with your audience. Your success, and their wellbeing, depends on it.

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