because it is “a simple action that can be performed by most people” and it “has an element of fun and delight to it.” While one can’t expect the author to prescribe these particular associations and anticipate all potential contextual nuances, identifying at least some of these associations could provide very helpful information for the designer who wishes to use these gestures in a meaningful, appropriate way. “Rotate to change state” for example, can be enriched by referring to our daily experience with faucets and other knobs that we encounter throughout daily life. (In the book’s introduction, the author brings up some interesting insights into the prevalence of gestural interfaces in public rest-rooms, yet he neglects to refer back to these very real objects when discussing how to actually apply these gestures to new interactive systems.) Surely these references will lose importance over time as objects we once knew disappear from contemporary everyday life. Nonetheless, the emotional meaning that physical objects evoke cannot be ignored when discussing any kind of gesture, and selecting the right gesture for a given context is a fundamental part of the design process.

While it is understandable that a book with a focus on touchscreens and interactive devices (and one that is published by O’Reilly, creator of so many software “bibles”) would necessarily be somewhat technical in its approach, it feels awkward to read about such a human subject as though it is a catalog of parts. It is odd, for example, to thumb through the appendix of actual human gestures presented in the format of a lengthy user manual for a new device. Though looking at these gestures in isolation is an interesting exercise, having such a detailed guide to something we all experience firsthand (the movement of our own bodies) is of questionable value. Since we already know these gestures innately, what requires reflection is how to apply them to an interaction design problem. It is not particularly interesting to read a description of “punch” as “A fist is pushed straight out in the air” or “hand gun” as “The hand is formed into the shape of a pistol, with the extended forefinger as the barrel and the thumb cocked upwards,” with possible uses being “selection, activation,” while being all too aware of what these gestures really imply to a human being either making them or

witnessing them being performed. Even something as seemingly mundane as “finger drum” has the potential for a richer communicative semantic

beyond “tapping out a rhythm.” The list of gestures is exhaustive and the photos are illustrative, but perhaps such quantity is unnecessary. It would be great to see more of a discussion of the significance of these gestures within the context of an interface narrative, even if only as a case study. For example, “Thumbing nose” states, “An offensive gesture, albeit a playful one”; it’s a description that begins to imply how the gestures offer social cues, but for the most part, the world sketched out in Saffer’s book is one in which a smile does little beyond triggering some specified system behavior.

Again, it is understandable that the focus of the book is to help designers determine specific ways to trigger software events from hardware-based inputs. It cannot be all things to all people, and the author does a good job of pointing the reader to resources for further investigation into other topics such as sign language, choreography, and body-lan-guage taboos. Still, it would be helpful to learn of at least one example where the social and cultural significance of the gestures was discussed in a way that could then allow the reader to get a glimpse into a process that considered these factors.

In Saffer’s preface he refers to this book as a “starting place and a reference point,” and ultimately, that is the best description for its role in any interaction designer’s collection of reading materials. It will be a great primer for students and a good introduction for others who are new to the field and need to quickly ramp up their knowledge of electronically enhanced, gesturally based interfaces. However for those who are familiar with the O’Reilly “animal series,” Designing Gestural Interfaces may come up short when compared to some other titles. For seasoned interaction and industrial designers, it can serve as a visual dictionary of sorts and will be helpful at the brainstorming stage, but may not be so useful when moving past that phase to the more critical parts of the design decision-making process.

ABOUT THE AUTHOR Carla Diana is an indus-
trial and interaction designer with a diverse back-
ground in design, technology, and product
research. Currently a senior interaction designer at
Smart Design in New York, she is working on a vari-
ety of projects from floor-cleaning appliances to
emotive robots. For more information, visit www.carladiana.com.

January + February 2009

DOI: 10.1145/1456202.1456214
© 2009 ACM 1072-5220/09/0100 $5.00