The final two post-survey questions asked participants to discuss when andhow they use design principles in design projects.In response to the question about when they rely on design principles andwhen they use empirical research such as usability testing or focus groups,the most common response placed design principles and design research in adynamic relationship.

Although participants offered diverse definitions, a number of the responsesused some form of one of the following terms:•guideline;•concept;•rule of thumb, heuristic, or strategy;•rule or prescription; or•tips and tricks, technique.By far the most common response centered on terms like “guideline,” “guide,”“guiding thought,” “practice that guides,” “idea which provides guidance,” andso forth.

What (if any) visual design principles did you learn about in your designeducation or training?• What (if any) visual design principles have you learned about through yourown reading?• What (if any) visual design principles do you use consciously in your designpractice?• What visual design principles do you think are important for new designersto learn?

Cluster analysis includes two general approaches: hierarchical and partitioning.Hierarchical cluster analysis also subdivides into two approaches: divisive andagglomerative, which is the most common. For my study I explored designprinciples using both agglomerative hierarchical and partitioning techniques.

The primary advantage of this online approach was quick and efficient accessto participants. However, there were two disadvantages. First, in a face-to-facecard sorting exercise, the researcher often observes the participant as he or shesorts the cards and uses the talk-aloud protocol to gather further informationabout participants’ thinking during the exercise. Because I would not attend thecard sorting, this kind of observation was not possible. Second, I would havelittle control over who agreed to participate. The possibility for spam is alwayspresent with online media

Having determined which design principles are mentioned most commonlyin literature on design, the next question is, how do these design principlesrelate to one another? Rather than arranging the design principles accordingmy own sensibilities or some separate theory (Ahmed [12], Park [13]), Idecided that it would be more interesting to ask practicing designers, designeducators, and design students how they think these 38 visual principles shouldbe grouped

This quantitative review produced a raw list of 198 design principles. Thisnumber might seem discouragingly high except for two outlying works: Leborg[54], which lists 41 principles, 33 of which are unique, and Lidwell et al. [58],which lists 100 principles, 87 of which are unique. Lidwell et al.’s broader focuson “universal principles of design” rather than visual design principles meansthat many of their principles fall outside of the scope of my study. (Some evenstretch the concept of design principle—for example, “uncertainty principle”and “normal distribution.”) If we were to exclude Leborg’s and Lidwell et al.’sunique principles, the list of design principles contracts from 198 to 77—stillhigh, but more reasonable. However, because I included unique principles fromother texts, I retained all of Leborg’s and Lidwell et al.’s principles in the raw list.As might be expected, some of these principles are considerably more commonthan most. Overall, of the 198 principles in the raw list, 160 were mentioned inonly one work. The 198 design principles were listed cumulatively 420 timesin the 46 texts; 61.9% of these listings referred to principles used in at leasttwo works. Despite the large number of unique principles, they were used onlyin 38.1% of texts

However, if an author combined related terms that other authors listed indi-vidually (for example, “similarity and contrast” in one work as opposed to“similarity” and “contrast” in another), I divided those terms so as to considerthem separately (similarity;contrast).

This persistence invokes some questions:•What is a design principle?•How do design principles relate to each other?•How and when do designers use design principles, particularly in these daysof user-centered, research-driven design?None of these questions have straightforward answers. Although many authorsrefer to design principles, hardly any define what they mean by the term

One would think from this narrative that we have progressed from the murkydays of the craft tradition to the more enlightened and progressive landscape ofempiricism. But, in fact, design training still typically involves an introductionto visual design principles, which persist as criteria for judging designs andas heuristics for making design decisions.