Perception and evaluation: optimizing computer imagery for communication

Computers are becoming faster and more interconnected creating a shift in their primary function from computation to communication. While the computer industry has produced faster processors, larger disk drives and higher memory capacity, these advances do little to help people understand the meaning of their data. This lack of understanding stems from the fact that machines process data in numerical form, while humans more easily comprehend visual data. Visualization is the process of using computer graphics to transform numerical data into meaningful imagery, enabling users to observe information. The resulting display allows a viewer to detect and analyze features in numerical data that may not have been recognized otherwise. The transformed data can be represented as a picture, an animation, or an interactive computer application. The art of visualization lies in choosing perceptual representations that maximize human understanding. This talk will demonstrate how perceptual psychology and visual art cognition provide the framework for new visualization methods. This iterative two-part process consists of using artistic computer graphics techniques to enhance the presentation of important data features, then conducting perceptual studies to evaluate the effectiveness of the resulting imagery. The strength of this approach lies in the synergy achieved in the tight coupling of the two research areas.Artistic images are often easier to understand than photographs. In their classic 1956 experiment, Ryan and Schwartz demonstrated that line drawings with exaggerated features of interest evoked a more rapid and accurate response than photographs or plain line drawings. More recently Gooch found increased learning speed using computer generated facial illustrations. NPR images convey information more effectively by: omitting extraneous detail; focusing attention on relevant features; and by clarifying, simplifying, and disambiguating shape. Control of detail in an image for the purpose of enhanced communication is becoming the hallmark of NPR. Control of image detail is often combined with stylization to evoke the perception of complexity in an image without explicit representation.What the eye perceives is not always what the mind comprehends. A general knowledge of perception can guide the creation of a visualization method. However, attempts to understand human cognition are hampered by the fact the workings of the mind cannot be observed. We must rely on external signs of cognition as exemplified in behavior. Therefore, there will always be a need to evaluate the effectiveness of the resulting imagery to insure optimal results. The effectiveness of an image can be evaluated by measuring its ability to communicate. Measuring the communication content of a image can best be performed in an indirect manner: a behavioral study is conducted in which participants perform specific tasks on sets of visual stimuli. If participants are statistically better at performing a task given a certain type of imagery, then that imagery can be said to be more effective for the given task. The ability to measure the communication content of imagery, means that empirical methods can be used to establish principles to validate methods.