Visual Explanations: Images and Quantities, Evidence and Narrative. - book reviews

Business Economics, April, 1998 by Edward J. Smith, Gregory Dawson

Presenting information, whether to a large group, to a small group, or even to a single person, now seems to require the creation and delivery of slick computer-generated graphics. The thought of giving a brief talk in this day and age, supplemented only by simple charts passed to participants, and without slide projectors or, in the author's words, "the dreaded overhead projector," is unthinkable. In his third book on data presentation and design, Visual Explanations: Images and Quantities, Evidence and Narrative, Professor Tufte of Yale University vividly demonstrates that anyone presenting information should rethink their concepts about how and why information is presented.

Visual Explanations departs from Tufte's earlier works in structure and content. Rather than a cookbook or a "how to" (or how not to) guide to the construction of visual displays of information, this book focuses on specific examples of what styles work well to illuminate the topic under examination. The book provides a combination of several case studies of good and bad visual design interspersed with hundreds of examples and illustrations of those designs that work well, those designs that work poorly, and those designs that do not work at all.

Professor Tufte enlightens the reader in the first chapters by demonstrating how presenting data can have lifesaving (or life-threatening) consequences. He uses the analysis performed by one of Queen Victoria's physicians, Dr. John Snow, concerning the London cholera epidemic of 1854. In analyzing the epidemic, Dr. Snow discovered the source of cholera by mapping the area where deaths had occurred and then by finding the common interactions among those who had died. Cholera victims clustered around a central point near a well pump on Broad Street in central London. Dr. Snow's mapping made vividly clear that victims all used the pump and that it was the source of water causing the epidemic. Professor Tufte highlights Dr. Snow's method of placing the data in an appropriate context for assessing cause and effect, thereby enabling him to make quantitative comparisons and to consider alternative explanations and contrary cases, and finally to assess possible errors in the numbers reported in the graphs.

The next reminder is the presentation used by Morton-Thiokol as the basis for the disastrous decision to launch the Space Shuttle Challenger in 1986. The Challenger space shuttle disaster demonstrates the effects of poorly designed and thought-through visual explanations. To recount the incident briefly, rubber O-rings in the shuttle's rocket motors did not seal properly at low temperatures. As a result, the motor exploded, killing the shuttle crew shortly after liftoff. In discussions with NASA prior to launch, Morton-Thiokol, the designer and builder of the rocket motors, initially recommended that NASA not launch the shuttle due to the forecast launch time temperature of -290 degrees F. That temperature was nearly 300 degrees colder than any previous launch. The Morton-Thiokol engineers assembled charts and graphs to explain their recommendation. Their poor data presentation included charts that displayed only the flights that suffered O-ring problems; the number was small compared to the total. When viewed in Tufte's way showing all flights, all of coldest launches had been between -530 to -630 degrees F, much colder that the expected -260 to -290 degrees, and all had O-ring problems. Other information presented at launch time was arrayed chronologically rather than by temperature. What was presented failed, in NASA's opinion, to support the no-launch recommendation. After further discussion, Morton-Thiokol reversed its no-launch recommendation, with its now infamous result. How information is displayed matters.

After the cases, Professor Tufte leads the reader through a series of chapters on what constitutes good design. His chapter on Magic, or visual deception, is a fascinating commentary on what not to do when designing explanatory presentations. Another example presents a (primarily) graphical design that consolidates complex patient medical history from reams of written information and thousands of data items into a single, high-resolution page, summarizing the patient's current condition and medical history.

His commentary on how information displays frequently mirror the organization structure of the presenting entity is especially insightful. For example, a news-broadcast method: as users approach an information kiosk, the computer plays a thirty-second video of the Director of the Museum welcoming the visitor, then a series of twenty-second videos of curators of various galleries introducing their territory, and then the Vice President for Facilities Management pointing at the telephones and rest rooms. In addition to resembling bad public television, such an approach commits a common error: the information architecture mimics the hierarchical structure of the bureaucracy producing the design. This also occurs in the design of magazines, as strongly colored frames delineate each subeditor's turf. Those accented borders and running heads, sometimes the strongest visual statement on the page, are not there to help the reader but rather to replicate the organizational form.