Perception and Visualization:

Perception is the capability of identifying and interpreting sensory input (nervous system - memory, expectation, attention and cognitive familiarity) derived from organism environment. Nervous system processing converts low-level information (shape, size, position) to high-level information (object-meaning-purpose). Human perception plays an important role in the area of visualization. Understanding of perception improves quality and quantity of displayed information.

What do we know about the role of perception in Visualization? As Cleveland and McGill article states Graphical Perception is the visual decoding of information encoded on graphs. It explains the science of graphs through human graphical perception. We know that preattentive vision, how it affects our graphical conclusion without paying much attention to details. Elementary Perceptual tasks are mental- visual tasks that viewer performs in order to extract the variables represented on graphs. Pie Charts, Bar charts, Statistical Maps with Shading, Curve-difference charts, Cartesian graphs, Triple Scatterplots, Volume Charts and Juxtaposed Cartesian graphs. we already know how they are used, however they also involves with judging data -perception in visualization. We know that Elementary tasks ordering is based on a combination of psychophysical theory and experimental results. The summary of experiments and Confidence interval also we know to detect patterns and organize the quantitative information.

As Heer and Bostock article supports, understanding perception is critical to effective visualization design. It discusses the new service “Crowdsourcing” for evaluating large design space of visualization. It provides the assessment of Amazon’s Mechanical Turk as platform for graphical perception experiments. We know that crowdsourcing is very attractive in visualization as it saves time and money as well as it enables experiments to canvas a wide range of subjects using their standard displays, effectively swapping experimental control for ecological validity.

The Perception in Visualization document discusses some theories in psychophysics - preattentive processing , post attentive processing and change blindness. Tasks that can be performed on large multi-element displays in less than 200 to 250 milliseconds are considered preattentive (low-level visual system). Postattentive vision shows that prior exposure to an scene does not help a viewer answer questions about the content of the scene. This article explains different theories with examples to demonstrate that what we see depends critically on where we focus. Perceptual properties of color, texture, motion and nonphotorealism have been used in what user see in the visual representation.

The other article explains how the hearing system is a valuable alternative for the understanding of complex data. Sonification is a term that describes the use of sounds not spoken in data representation, aiming always at the most adequate manner of carrying information. Why it is important? As Cleveland and McGill article supports perception is important in order to identify Elementary perceptual tasks and understand in which order those tasks are performed based on how people extract quantitative information from graphs. Thus, this psychophysical theory provides guidelines for graph construction: graphs should employ elementary task as high in the ordering as possible in order to get the most accurate prediction of graphical forms. Radical surgery on popular graphs is needed and need to replace them with graphs such as dot charts, dot charts with grouping and framed-rectangle charts. It is important to identify perceptual building blocks to develop a framework to organize knowledge and predict behavior. The ordering of the perceptual tasks provides a set of guidelines that must be used with judgements in designing a graph. Crowdsourcing is important service as it is available with low cost, scalability , viable and contributes new insight for visualization design. By integrating crowdsourcing tools with web-based experiment design tools, an entire class of user studies may be subject to cheap, scalable web-based design and deployment. Moreover, by archiving and disseminating HIT definitions, such tools might also greatly facilitate study replication, comparison, or modification.

Sonification can be a good solution to help the mapping of data associated to difficult standards of visual perception; in particular, data of great size and with varied dimension.

References: 1.https://web.fe.up.pt/~tavares/downloads/publications/artigos/IJI_Manuscript_DA_JT.pdf 2.https://www.csc2.ncsu.edu/faculty/healey/PP/ 3. Cleveland and McGill 4. Heer and Bostock 5. Moodle (http://moodle.harrisburgu.edu/pluginfile.php/296031/mod_resource/content/0/Graphical_perception.html#/perception-processes)

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