Cognitive Issues & User TasksCS 4460/7450 - Information VisualizationJanuary 22, 2009John StaskoSpring 2009 CS 4460/7450 2Outline• Overview• 1. Role – How visualizations aid cognition?• 2. Tasks – What does the visualization assist?Spring 2009 CS 4460/7450 3Basic Premise• Understanding (the cognitive aspects) is the crucial part of InfoVis• Visualization is simply a tool useful for aiding analysis, exploration, comprehension and understanding• Discussed the role of external cognition aids briefly earlier in intro, more nowSpring 2009 CS 4460/7450 4How Are Graphics Used?• What does a visualization or graphic image provide for us?Spring 2009 CS 4460/7450 5How Are Graphics Used?• Larkin & Simon ‘87 investigated usefulness of graphical displays• Graphical visualization could support more efficient task performance by:− Allowing substitution of rapid perceptual influences for difficult logical inferences− Reducing search for information required for task completion• (Sometimes text is better, however)Spring 2009 CS 4460/7450 6Norman’s Thoughts• Cognitive Artifacts− Wonderful discussion on p. 49• Matching Representation to Task− Tic-tac-toe, flight schedules• Representations Aid Info Access and Computation− Medical prescriptions, Roman numerals, maps & legends• Naturalness and Experiential Cognition“Visual Representations”Chapter 3 fromThings That Make Us SmartSpring 2009 CS 4460/7450 7Visualization• Often thought of as process of making a graphic or an image• Really is a cognitive process− Form a mental image of something− Internalize an understanding• “The purpose of visualization is insight, not pictures”− Insight: discovery, decision making, explanationRevisitSpring 2009 CS 4460/7450 8Main Idea• Visuals help us think− Provide a frame of reference, a temporary storage area• Cognition → Perception• Pattern matching• External cognition aid− Role of external world in thinking and reasonLarkin & Simon Larkin & Simon ’’8787Card, Mackinlay, Shneiderman Card, Mackinlay, Shneiderman ‘‘98 98 RevisitSpring 2009 CS 4460/7450 9Visualization• Definition− “The use of computer-supported, interactive visual representations of data to amplify cognition.”From [Card, Mackinlay Shneiderman ‘98]RevisitExamine More Closely• What does “amplify cognition” mean?• DiscussSpring 2009 CS 4460/7450 10Another View• Leverage Hutchins’ theory of distributed cognition (DCog) to explain the value and utility of infovis• Use DCog as a supporting theoretical framework for infovisSpring 2009 CS 4460/7450 11Liu, Nersessian, StaskoTVCG ‘08Amplifying Cognition• Hutchins argues that tools don’t amplify or scaffold cognition (a more traditional cognitive science view)− Eg, Our memory isn’t amplified• Instead, tools help transform the analytic process into another more doable oneSpring 2009 CS 4460/7450 12Distributed Cognition• Cognitive system is composed of people and the artifacts they use− Cognition isn’t only internal• Changes in external representation spur changes in internal representation and understanding• It is interaction with the external representations that drives this processSpring 2009 CS 4460/7450 13More Details• OK, so now let’s talk about the analytic process in more detail, and specifically, how visualization can play a roleSpring 2009 CS 4460/7450 14Spring 2009 CS 4460/7450 15Understanding• People utilize an mental/internal model that is generated based on what is observed• B. Tversky calls the internal model a cognitive map− Think about that termSpring 2009 CS 4460/7450 16Example• You’re taking the MARTA train to get to Georgia State University− You have some existing internal model of the system, stops, how to get there− On train, you glance at MARTA map for help− Refines your internal model, clarifying items and extending it− Note that it’s still not perfect, no internal model ever isSpring 2009 CS 4460/7450 17Cognitive Map• Just don’t have one big one• Have large number of these for all different kinds of things• Collection of cognitive maps --> Cognitive collageSpring 2009 CS 4460/7450 181. Process Models• (Recall the user and cognitive models from HCI?)• Process by which a person looks at a graphic and makes some use of it− A number of substeps probably exist• Can you describe process?Spring 2009 CS 4460/7450 19Process Model 1• Robert Spence•Navigation- Creation and interpretation of an internal mental modelSpring 2009 CS 4460/7450 20NavigationContentBrowsingstrategyInternalmodelInterpretationBrowseModelInterpretFormulate abrowsingstrategySpring 2009 CS 4460/7450 21Interpretation• Can someone explain that?Spring 2009 CS 4460/7450 22Interpretation• - Content is the display on screen - Modeling of that pattern results in cognitive map - Interpretation (ah, variables x and y are related) leads to new view, that generates an idea for a new browsing strategy- Look at the display again with thatSpring 2009 CS 4460/7450 23Process Model 2• Card, Mackinlay, Shneiderman book• Knowledge crystallization task− Gather info for some purpose, make sense of it by constructing a representational framework, and package it into a form for communication or actionSpring 2009 CS 4460/7450 24Knowledge Crystallization• Information foraging• Search for schema (representation)• Instantiate schema• Problem solve to trade off features• Search for a new schema that reduces problem to a simple trade-off• Package the patterns found in some output productFrom CMS ‘98Spring 2009 CS 4460/7450 25How Vis Amplifies Cognition• Increasing memory and processing resources available• Reducing search for information• Enhancing the recognition of patterns• Enabling perceptual inference operations• Using perceptual attention mechanisms for monitoring• Encoding info in a manipulable mediumSpring 2009 CS 4460/7450 26ProcesstaskRawdataDatatablesVisualStructuresViewsDatatransformationsVisualmappingsViewtransformationsSpring 2009 CS 4460/7450 27Knowledge CrystallizationInstantiateschemaSearch forschemaForagefor dataProblem-solveAuthor,decideor actTaskExtractComposeRead factRead comparisonRead patternManipulateCreateDeleteInstantiateReorderClusterClassAveragePromoteDetect patternAbstractOverviewZoomFilterDetails-on-demandBrowseSearch querySpring 2009 CS 4460/7450 282. User Tasks• What things will people want to accomplish using