Signal-to-Noise ratio and the elimination of the nonessential
March 12, 2007
One of the coolest, most useful books I have on my shelf is Universal Principles of Design. This is a beautifully simple book and one that is immensely useful, a must for professionals and leaders from any discipline. The subtitle of the book pretty much sums it up: "100 Ways to Enhance Usability, Influence Perception, Increase Appeal, Make Better Design Decisions, and Teach Through Design." Even trained designers will want this book somewhere on their shelf. Each of the 100 principles — most of them applicable to presentation design — is summarized with great clarity and with good visual examples in just two pages. References are given for each principle for those who want to go deeper, but for a quick reference, this book can't be beat.
The principles are presented in alphabetical order, beginning with "80/20 Rule" and "Accessibility," and finishing 210 pages later with "Uncertainty Principle" and "Weakest Link." Between the principles of "Shaping" and "Similarity" you will find a good summary of the "Signal-to-Noise Ratio" (SNR). The SNR principle is borrowed from more technical fields such as radio communications and electronic communication in general, but the principle itself is applicable to design and communication problems in virtually any field. The authors sum up the signal-to-noise ratio this way:
The ratio of relevant to irrelevant information in a display. The highest possible signal-to-noise ratio is desirable in design.
Above: A couple of older slides (from a Steve Ballmer keynote in 2005) with rather low signal-to-noise ratios.
Above: Even Steve Jobs can present simple data in a way that complicates rather than simplifies (or did the faux marble texture and 3D help illuminate?). Note too that the baseline starts at 1000 (though it is hard to tell where the baseline is).
"Excess is noise"
Ensuring the highest possible signal-to-noise ratio means communicating (designing) clearly with as little degradation to the message as possible. Degradation to the message can occur in many ways such as with the selection of inappropriate charts, using ambiguous labels and icons, or unnecessarily emphasizing items such as lines, shapes and symbols, etc. that do not play a key role in support of the message. In other words, if the item can be removed without compromising function, then strong consideration should be given to minimizing the element or removing it all together. For example, lines in grids or tables can often be made quite thin, lightened, or even removed. And footers and logos, etc. can usually be removed with good results (assuming your company "allows" you to). In a nutshell, the authors put it this way:
Every element in a design should be expressed to the extent necessary, but not beyond the extent necessary. Excess is noise.
In Visual Explanations, Edward Tufte refers to an important principle in harmony with SNR called "the smallest effective difference":
"Make all visual distinctions as subtle as possible, but still clear and effective."
— Edward Tufte
Related to the smallest effective difference is Occam's razor, which both Tufte and the authors of The Universal Principles of Design point out. Tufte sums up the Occam's razor this way:
"What can be done with fewer is done in vain with more."
Tufte goes on to say that a "...happy consequence of an economy of means is a graceful richness of information, for small differences allow more differences."
Above: This is a fake "Before" slide I made up rather quickly. The data being displayed is extremely simple, yet the eyes have to work pretty hard to get at the data. 98 new members in the first quarter of 2007 would be a very significant fact for the club, but perhaps a declarative sentence on the slide rather than a title would be more appropriate. The "noise" can be reduced in myriad ways (below).
Above: Examples of simpler ways to show the same data. Even the baseline was removed (left) since the bars define the endpoint, still a thin baseline may be appropriate as Tufte points out in The Visual Display of Quantitative Information. There are many ways to display this kind of basic data; the two slides above are not necessarily "the best" way.
But is the non-essential always "noise"?
Do design elements which are not absolutely essential necessarily detract from a design? Occam's razor says that unnecessary elements decrease the design's efficiency and increase the possibility of unintended consequences. But does this mean that we must be ruthless and remove everything which is not absolutely "essential" to a design? There are those who say a minimalist approach is certainly best (and also beautiful); I tend to fall in to that camp. But efficiency itself is not necessarily an absolute good or always the ideal. (Would one admire the work of an efficient purse-snatcher for example?) Nonetheless, when it comes to the display of quantitative information (charts, tables, graphs, etc.), I strongly favor display designs which include the highest SNR as possible. With other visuals, however, we may want to consider including or retaining elements which serve to support the message at a more emotional level. This may seem like a contradiction with the principle of a high SNR, or the Occam's razor, and the idea that "less is more." However, sometimes emotional elements matter (sometimes a lot). John Maeda pointed this out in his book, The Laws of Simplicity. Maeda insists that the principle of reduction (removing the nonessential) is important, but he also admits that emotion is very important as well and that often more emotion is better than less:
"When emotions are considered above everything else, don't be afraid to add more ornament or layers of meaning."
— John Maeda
Design makes things clear, Maeda says, but art — the stuff of emotions — makes us wonder. Design can bring clarity to a message, art can help bring meaning. "Sometimes...clarity alone is not the best design solution." Presentation design is as much art as it is science, and, of course, aesthetics do matter. The Aesthetic-Usability Effect (also in the Universal Principles of Design) says that "aesthetic designs are perceived as easier to use than less-aesthetic designs." First impressions based on aesthetics are important, for example, as the way people think about or interact with a design will be influenced at some level by how the design looks or feels (to them). Clarity and the reduction of the nonessential are important, but we need to remember too that how a design looks influences perception.
The Google website is often mentioned when talking about sites that have cut everything visually except that which is essential. Yet there is emotion there too; the logo is large, colorful, and even "playfully seasonal."
As with all things...balance
Understanding what is noise and what is excess is an important design consideration. As pointed out in this paper by Michael Albers on SNR in documentation, what is considered noise will depend on the context. "An excess of noise can occur from either too much or too little information," says Albers. "... much of the real difficulties in communicating information do not fall within the technical realm. [They] fall within the people realm which revolves around the contextual aspects of the information." Use depends, then, on our particular circumstance, audience, and objectives. Ideas like SNR are good principles, but not rules to be blindly followed. In my opinion, designs with a high signal-to-noise ratio are not only generally clear, they often look good as well. But in the end, SNR is one principle among many to consider when creating visual messages.
Related links from Presentation Zen
• 2-D or not 2-D
• Noise and the elimination of the non-essential
• Wabi-Sabi and Presentation Visuals (part I)
• Wabi-Sabi and Presentation Visuals (part II)
• Wabi-sabi simplicity as it relates to interface design (from 37 Signals)