Consider as Many Design Alternatives as Possible: The Value of Parallel Design
by Dr. Bob Bailey
Several years ago I taught several "hands-on" courses on Web user interface design. In one exercise, students were given user and system requirements, and used a prototyping tool to create a simple system. After the design solutions were completed, each individual in the class used everyone else's proposed systems to complete a task. Having experienced everyone else's ideas, the students then made changes to their original prototypes. The same process was repeated a second time.
The results were amazing. By having students work independently to create unique ideas, and then effectively sharing these ideas, the final interfaces always were significantly better than the originals. A second major observation was how quickly students found and perpetuated good design ideas in their own products.
Benefits of the Approach
A few years later, Jakob Nielsen (1993) described a development methodology that proposed using a process in which several different designers work out possible designs. The aim was to develop and evaluate different ideas before settling on a single approach. He suggested that the designers work independently, since the goal of this approach was to generate as much diversity as possible. Once they had created different designs, they combined their different ideas and took the best features from all designers.
Nielsen outlined the major benefits of using this approach:
- Allows a range of ideas to be generated quickly and cost effectively;
- Allows several approaches to be explored at the same time, thus compressing the concept development schedule;
- The concepts generated often can be combined so that the final system benefits from all ideas;
- Those with little usability expertise can use the technique.
The primary limitation is that the method requires a number of design team members (5-10) to be available at the same time to produce the design ideas.
Ovaska and Raiha (1995) published an article demonstrating that having designers make initial design decisions independently, and then combining their results, resulted in far better user interfaces. They called this approach "parallel design.” Five years later, Macbeth, Moroney and Biers (2000) found that having the original decisions made by several individuals was good, but that the original group then should evaluate all independent submissions and determine the best design solutions.
More recently, John McGrew (2001) published an article where he confirmed the validity of parallel design. He applied a parallel design process to develop a user interface for an invoice reconciliation program. To do this, McGrew scheduled a one-day session with several participants. He included the project manager, one person from the software and hardware design teams, two subject matter experts, a technical writer that was scheduled to do the training, three users and himself (a human factors engineer).
They began by having each person in the group independently sketch a proposed user interface on a large sheet of paper using colored felt-tip markers. The sketches then were posted on the wall for all to see and evaluate.
After viewing the design solutions proposed by others, each participant sketched two new designs. McGrew required that their new design include at least one idea from another person's design, and include an idea that no one else yet had proposed. Again, all participants reviewed all the design solutions. Participants began to agree on an optimal design fairly early in the process, and were able to reach a consensus on the final user interface design before the end of the day.
What is most striking, however, is that most traditional design processes only would have considered a few iterations of a single design. Using a parallel design approach like they did here, the design team considered 40 design alternatives before beginning the iterative process, i.e., before doing any usability testing. Consistent with my observations a few years ago, McGrew also found that participants responded immediately to good ideas. This was true even when good ideas were contained in otherwise poor design solutions.
Good user interface design requires designers first to "saturate the design space." This means that designers should consider as many alternative design ideas as possible before selecting the best with which to begin the iterative design and testing process. It is also worth noting that after ideas generated in parallel design are designed, usability testing is required to validate the design solutions. It is very possible to have good ideas designed incorrectly.
Macbeth, S.A., Moroney, W.F., & Biers, D.W. (2000), Development and evaluation of symbols and icons: A comparison of the production and focus group methods, Proceedings of the IEA 2000/HFES 2000 Congress, 327-329.
McGrew, J. (2001), Shortening the human computer interface design cycle: A parallel design process based on the genetic algorithm, Proceedings of the Human Factors and Ergonomics Society 45th Annual Meeting, 603-606.
Nielsen, J. (1993)., Usability Engineering., Boston: Academic Press
Ovaska, S., & Raiha, K.J. (1995)., Parallel design in the classroom, Proceedings of CHI'95, 264-265.