Multi-touch pinch gestures: performance and ergonomics

Multi-touch gestures are prevalent interaction techniques for many different types of devices and applications. One of the most common gestures is the pinch gesture, which involves the expansion or contraction of a finger spread. There are multiple uses for this gesture--zooming and scaling being the most common--but little is known about the factors affecting performance and ergonomics of the gesture motion itself. In this note, we present the results from a study where we manipulated angle, direction, distance, and position of two-finger pinch gestures. The study provides insight into how variables interact with each other to affect performance and how certain combinations of pinch gesture characteristics can result in uncomfortable or difficult pinch gestures. Our results can help designers select faster pinch gestures and avoid difficult pinch tasks.