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Visual Momentum Given that meaningful activities often involve moving across displays, designers should be able to aid the transition from one view into the artificial data field to another. The concept of Visual Momentum is borrowed from perception and cinematography (Hochberg, 1986) and refers to the impact of a transition from one view to another (a cut in cinematography) on the cognitive processes of the observer, in particular on the observer’s ability to extract task-relevant information. As applied to HCI, “the amount of visual momentum supported by a display system is inversely proportional to the mental effort required to place a new display into the context of the total data base and the user's information needs. When visual momentum is high, there is an impetus or continuity across successive views that supports the rapid comprehension of data following the transition to a new display” (Woods, 1984, p. 231). At one end of the dimension lies poor transitions which consist of (a) total replacement of one view for another and (b) the absence of any visible cues to the virtual field of possible views. When Visual Momentum is low, each “glance” into the artificial data field is independent of previous glances so that the observer must reorient from scratch to each new view as it is called into the limited viewport. At the other end of the dimension the observer works within a conceptual space in which individual views are grounded. A conceptual space depicts relationships in a frame of reference (Woods, 1995a; 1996). In between lies a variety of techniques for building a sense of a conceptual space analogous to a physical space so that orienting and moving about the virtual perceptual field can employ the same perceptual and cognitive processes that allow us to fluently explore and reorient to new events and changing views in naturally occurring physical spaces. Some of the techniques to increase Visual Momentum are longshots, landmarks, content-laden cues to structure, spatial dedication, coordinating what can be seen in parallel and what in series as a function of task demands (Henderson and Card’s “rooms”), center-surround, side effect views, cues to status. All of these techniques and many others (e.g., trails, bookmarks, 3D spatial metaphors) function as visible cues to the structure of the space of possibilities and cues to the status of those different parts of the domain represented by the artificial data field behind the keyhole. Designers can orchestrate these kinds of techniques to create what the user experiences as a tangible conceptual space to support effective workspace coordination. |