Information Visualization Principles, Techniques, and Software

Perceptual Properties Of all the human senses, vision is considered a primary and powerful channel of input. It takes in everything from the world around us and transmits this information to the brain for an instant analysis of what it means. With this intimate connection that vision has with cognition comes the first step toward learning and creating visual designs, which is through understanding how human visual perception works. Visual perception is relative, constantly scanning, constantly adjusting focus, and constantly adapting. A well-known example, which is presented in figure 2.1, demonstrates how written words are perceived in a way that is different from what most people may initially think. According to research in word recognition and how the human brain reads letters, the order of letters in a word does not matter; the only important thing is that the first letter and last letter are in the right place. (1) Our vision relays the information to our brain, which takes care of processing what has been seen. Even when an entire paragraph contains numerous spelling errors, people can still comprehend it without any problems and often without even realizing that there are any errors in the text. Figure 2.1 serves as a nice demonstration of how human vision and cognition interact: the human mind does not read every letter by itself; instead, it processes the word as a whole. This example also illustrates the complex and mysterious nature of human vision. Even more, it creates extensive opportunities for visual designers to take advantage of human visual perception as it pertains to information visualization. Among all the unique characteristics of vision, two perceptual properties are commonly applied in information visualization: pre-attentive processing and the Gestalt Laws. Figure 2.1 Word recognition: how our brain reads letters (from Jinxi Caddel, "Word Recognition: How Our Brain Reads Letters," Learn, Think, Inspire [blog], February 4, 2010, www.jinxi boo.com/blog/2010/2/4/word-recognition-how-our-brain -reads-letters.html). I cdnuolt blveiee That I cluod aulacty uesdnatnrd what I was rdanieg. The phaonmneal pweor of the hmuan mnid Aoccdrnig to rscheearch at Cmabridge Uinervtisy, It deosn't mttaer in what oredr the Itteers in a wrod are, The olny iprmoatnt thing is That the first and last Itteer be in the rghit pclae. The rset can be a taotl mses and you can still raed it wouthit a porbelm. This is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe. Amzanig huh? What the above text says: I couldn't believe That I could actually understand what I was reading. The phenomenal power of the human mind. According to research at Cambridge University, It doesn't matter in what order the letters in a word are, the only important thing is That the first and last letter be in the right place. The rest can be a total mess and you can still read it without a problem This is because the human mind does not read every letter by itself, but the word as a whole. Amazing, huh? Pre-attentive Processing Pre-attentive visual processing, which takes place in the sensory memory, is fundamental for creating visual representations. Pre-attentive visual attributes are perceived by viewers almost instantaneously and without the intervention of consciousness. One of the key issues in the study of information visualization is to investigate how the human visual system processes and analyzes an image. An important initial result of this research was that a small number of visual properties can be detected rapidly and accurately simply by the "low-level" visual system. These properties were termed pre-attentive since their detection appears to precede focused attention. (2) It may be difficult to fully perceive the value of this insight, but understanding pre-attentive processing is important for visualization design. In particular, by exploiting pre-attentive processing capability, several important design questions can be answered, such as, What can be perceived immediately? …