Iterative Design

You’re on a quest to design the perfect brownie recipe for your food blog. After hours of online research, reviewing cookbook after cookbook, you come up with a prototype. You bake it, taste it, and share your creation with your friends. You ask for their feedback and a major note is that the texture is not quite right. It’s far too cakey and not fudgy enough. It’s back to the drawing board. You rework the recipe and present the updated version. The good news is that they loved the consistency, but a lot of them mentioned that the baked goods were too sweet. You return to the kitchen to make the final few adjustments, and you think you’ve hit a home run. Your friends take one bite in and all you hear is compliments. That’s it, you managed to develop the best brownie recipe. Time to share it with everyone! 

This process of gradually refining a brownie recipe is a simple example of an established form of design methodology known as iterative design. The cyclical process of iterative design focuses on making incremental progress towards the final product. Each iteration builds upon the previous one, gradually refining the design based on user feedback and testing results.

Rather than attempting to design the perfect product in one go, designers first start with a prototypical, or basic version, of the product. The insights gathered from product testing are used to inform the design team of any necessary changes or improvements. Designers repeat prototyping, testing, analyzing, and refining until the product reaches the desired level of quality and functionality.¹ It’s a common technique that can be applied to various industries, particularly prominent in the world of user experience (UX), human-computer interaction (HCI), and digital product.

The iterative design cycle consists of 4 key phases:²

1. Identifying the Problem and Research: Design teams outline the issues they would like to solve (for the initial prototype or in subsequent iterations). They consult the literature and reference relevant product feedback.

2. Developing Ideas and Solutions: Designers engage in brainstorming sessions, drawing up diagrams and creating design specifications. A version of the product is developed based on the proposed design specification. Prototyping is crucial as it provides a tangible version of the product for internal review and quick user feedback, even before formal testing.

3. Testing the Solution: The version gets tested on users and feedback is gathered. This phase assesses beyond usability to include other key metrics like engagement, efficiency, and error rate, depending on the product goals.

4. Evaluating the Solution:  Evaluation should lead directly to the decision-making process on what the next steps are: whether to iterate further based on feedback, pivot the design concept entirely, or move towards finalization. This phase includes prioritizing feedback and determining the scope of the next iteration.

Image Source: What Is Iterative Design? Radiant Digital (2021)

Iterative design is closely linked to another method known as incremental development. Despite their fundamental differences, the terms are often lumped together or used interchangeably. Where do they differ? Incremental development focuses on adding a new feature to the design one by one until a complete product is reached—like ascending a staircase. Conversely, the iterative design process is based on a cyclical pattern that involves constant refinement and testing before deciding on a final version of the product.  

At the heart of the iterative design process is testing.³ Testing is a precious tool for those striving to improve their product, it involves asking critical questions, getting feedback from others, and conducting research to identify gaps that can be filled in future iterations of the product. In a nutshell, the purpose of the iterative design process is to end up with the best possible version of the product.

Usability Testing: A research methodology for evaluating products or services by testing them on real users. By learning about the target users’ behavior and preferences, a usability test aims to identify problems in product design and uncover opportunities for improvement. 

Minimum Viable Product (MVP): The most basic version of a product that contains just enough of the vital features for early product testers to try it out and give feedback on it for future development. 

Human-Computer Interaction (HCI): A multidisciplinary field concerned with understanding the interaction between humans, or the user, and the computer. It encompasses the design, evaluation, and implementation of interactive computing systems for human use.

Prototype: The preliminary version of a product, system, or interface. It is used to test and validate design specifications and usability before a final model is made. It is a key aspect of the design and development process in numerous fields.

Iterative design has its roots in engineering, where a multi-prototyping process is often used to improve the quality and functionality of a product. It formally dates back to the 1930s when a quality expert at Bell Labs, Walter Shewhart, proposed a cyclical method to improve product quality. He laid the groundwork of what became known and popularized by W. Edwards Deming as the “plan-do-study-act” (PDSA) cycle.⁴

The PDSA cycle consists of 4 stages:

1. Plan: Identify the opportunity for improvement, set objectives, and develop a plan for addressing it.

2. Do: Carry out the plan. This involves testing in a controlled environment.

3. Study: Evaluate the results gathered from testing. Analyze and determine whether the plan had the desired effect.

4. Act: Based on the insights from the study phase, take the appropriate action. Whether it is to standardize the change if successful or refine the plan if unsuccessful.

By the 1970s, the iterative design process had become a popular method of development in the software engineering field. A pioneer in software engineering, Harlan Mills, advocated for user participation and emphasized the importance of testing designs with actual users as a means for designers to learn.

User testing is the focal point of contemporary iterative design processes, especially with the concentrated effort on user-centered design. Techniques such as usability testing, user interviews, and prototyping are a few of the many ways designers gather feedback to inform iterative improvements.

 Today, sophisticated technological advancements have quickened the pace of iterative design. Tools like rapid prototyping that provide real-time analytics have been developed to help facilitate designers’ ability to meet the accelerated changes in user needs.

How we think we will behave is not necessarily a reflection of how we will actually act. Because of this, product prototypes are simply a reflection of their theoretical use until feedback is gathered and used to improve the product. The iterative design cycle recognizes the discrepancy in users’ real behavior and predicted behavior. How? Through iterative design, prototypes can be quickly developed and tested to see if users are behaving the way that we think they will. After product testing, consumer feedback can be utilized to redesign the product, bringing it closer to its peak usability. Early revisions require fewer major changes, thus each iteration is more cost-effective than it would be to start over completely.⁵

On top of that, consulting users for feedback throughout the process assures that design developments are meeting user needs as well as adding value to the overall product. Remember that one of the goals of iterative design is to get as close to what the user expects, making it more intuitive. What better way to achieve this than by asking the users directly and making improvements based on their feedback? 

Although the iterative design process has been hailed for its ability to help products meet user needs, two issues plague it.

A major critique is that iterations limit innovation. Some have gone as far as questioning whether iterations are designs at all.⁶ The logic is that developing a product purely based on feedback puts a ceiling on the designer’s creativity. A product is only “getting better” as usability issues are being addressed, but what if the best version of a product requires an entirely new design? ‘One-size’ doesn’t fit all, some experts advocate for using more than one design method for any given product. For instance, merging the iterative design process with incremental development opens doors for designer creativity whilst addressing user needs.

Relying on user feedback for design advice only helps identify usability issues but doesn’t solve them. When providing our opinions on a product’s performance, we often find it easy to identify what is wrong. But gathering solutions, or how to fix the issue is a much more arduous task. After receiving feedback designers are responsible for turning words into action. They must do so in a way that responds to all of the critiques from multiple (and sometimes conflicting) viewpoints. 

Uber’s User Research 

Uber simplified ride-hailing services by condensing everything into an app. In just a couple of taps, you have a car driving to pick you up in front of your door within minutes. But, like any product, Uber had once faced issues with usability. 

Hoping to put an end to these problems, Uber invested in UX research and iterative design processes. They made use of focus groups, surveys, and in-app feedback to help identify areas that were pain points for their users. Airing out the exact issues their users were having with the app allowed Uber to go through an extensive iterative design process. After multiple rounds of user testing and feedback, closely working with UX designers to create and iterate prototypes, Uber has found solutions that would enhance the app experience.⁷

Some of the design changes included simplifying the search bar, implementing a bottom menu bar for easier app navigation, and giving users the option to choose their preferred mode of transportation. These changes were met with positive feedback and an increase in customer engagement and loyalty. This case study on Uber demonstrates just how powerful the iterative design process is in improving app designs.

TD Bank’s App Update

TD’s new app redesign offered improved functionality and a simplified digital interface. This is all due to the work achieved at the Bank’s Human-Centered Design (HCD) research arm. The focus was to update the app to reflect their commitment to providing an accessible and human-first design. By researching the needs of their customer base, TD was able to bring to light the obstacles they were encountering with the system.

In turn, the TD Invent department took a dynamic test-and-learn approach, which ultimately was the iterative design process, to make gradual improvements to the app. Iteration after iteration culminated in a dramatic app redesign that provided a sleek interface and increased usability.⁸ This goes to show that listening to customer feedback can drastically enhance their app experience.

A/B Testing

A key aspect of the iterative design process is to receive user feedback through testing. This article outlines a form of user testing that compares two or more versions of a product to determine which performs better. Designers can learn the impact of each product change on their users which goes on to inform future changes.

The Mistake That Almost Half of Product Managers Make

Inherent cognitive biases taint the reliability of the insights gathered from user testing, but as it turns out, product managers are just as prone to these biases. A TDL investigation revealed nearly half of product managers would take the irrational route when deciding whether to implement product design changes following a round of user testing. It seems that strictly following pre-set academic standards isn’t always a significantly better action.

1. Eby, K. (2019, January 2). All about the Iterative Design Process. Smartsheet. https://www.smartsheet.com/iterative-process-guide#:~:text=The%20iterative%20process%20starts%20with
2. Interaction Design Foundation. (2023). Design iteration brings powerful results. So, do it again designer! The Interaction Design Foundation; UX courses. https://www.interaction-design.org/literature/article/design-iteration-brings-powerful-results-so-do-it-again-designer
3. Nagulwar, A. (2023, April 5). Reimagining product design with iterative design process: A UX guide. Aubergine. https://auberginesolutions.com/blog/a-ux-designers-guide-to-iterative-design-process/#:~:text=The%20entire%20iterative%20UX%20design
4. Larman, C., & Basili, V. R. (2003). Iterative and Incremental Developments: A Brief History. Computer, 36(6), 47–56. https://doi.org/10.1109/mc.2003.1204375
5. See 2. 
6. DreamerUX. (2017, March 20). Iteration Is Not Design - Debunking Design Darwinism. DreamerUX. https://www.dreamerux.com/articles/gme22a625m4te6n7aph33w7gkwpt2g
7. Abdullayev, A. (2023, March 9). How Uber Used UX Research to Improve the Ride-Hailing Experience. LinkedIn. https://www.linkedin.com/pulse/how-uber-used-ux-research-improve-ride-hailing-a%C4%9Fasif-abdullayev/
8. TD Bank. (2023, October 16). Human-centred design at TD. TD Stories. https://stories.td.com/ca/en/article/td-invent