Cognitive Issues & Human Tasks

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Cognitive Issues &

Human Tasks

CS 7450 - Information Visualization January 13, 2004

John Stasko

Outline

• Overview

• 1. Role – How visualizations aid cognition?

• 2. Tasks – What does the visualization assist?

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Basic Premise

• Understanding (the cognitive aspects) is the crucial part of InfoVis

• Visualization is simply a tool useful for aiding comprehension and understanding

• Discussed the role of external cognition aids briefly last time

How Are Graphics Used?

• What does a visualization or graphic image provide for us?

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How 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

Cognitive Map

• What is it?

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Understanding

• People utilize an internal model that is generated based on what is observed

• Tversky calls the internal model a cognitive map

−Think about that term

Example

• 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 is

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Cognitive Map

• Just don’t have one big one

• Have large number of these for all different kinds of things

• Collection of cognitive maps --> Cognitive collage

1. 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?

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Process Model 1

• Spence

• Navigation - Creation and interpretation of an internal mental model

Navigation

Content

Browsing

strategy Internal

model

Interpretation

Browse Model

Interpret Formulate a

browsing strategy

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Interpretation

• Can someone explain that?

Interpretation

• 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 that.

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Process Model 2

• Card, Mackinlay, Shneiderman

• 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 action

Knowledge 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 product

From CMS ‘98

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How 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 medium

Process

task

Raw data

Data tables

Visual

Structures Views

Data

transformations Visual

mappings View

transformations

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Knowledge Crystallization

Instantiate schema Search for

schema Forage for data

Problem-solve Author,

decide or act Task

Extract Compose

Read fact Read comparison Read pattern Manipulate Create Delete Instantiate

Reorder Cluster Class Average Promote Detect pattern Abstract Overview ZoomFilter

Details-on-demand Browse

Search query

Intermission

• HW 1

−Challenging?

−Interesting ones?

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2. User Tasks

• What things will people want to accomplish using information visualizations?

• Last time, we discussed

−search vs. browsing

Browsing vs. Search

• Important difference in activities

• Appears that information visualization may have more to offer to browsing

• But…browsing is a softer, fuzzier activity

• So, how do we articulate utility?

−Maybe describe when it’s useful

−When is browsing useful?

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Browsing

• Useful when

− Good underlying structure so that items close to one another can be inferred to be similar

− Users are unfamiliar with collection contents

− Users have limited understanding of how system is organized and prefer less cognitively loaded method of exploration

− Users have difficulty verbalizing underlying information need

− Information is easier to recognize than describe

Lin ‘97

Tasks

• OK, but browsing and search are very high level

• Let’s be more specific…

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Example from Last Time

Example courtesy of Chris North

Which state has the highest income?

Is there a relationship between income and education?

Are there any outliers?

Questions:

Exercise

• What are the (types of) tasks being done here?

• Can you think of others?

−Let’s develop a list

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Task Taxonomies

• Number of different ones exist, important to understand what process they focus on

−Creating an artifact

−Human tasks

−Tasks using visualization system

−...

User Tasks

• Wehrend & Lewis ‘90 created a low-level, domain independent taxonomy of user tasks in visualization environments

• Eleven basic actions

−identify, locate, distinguish, categorize, cluster, distribution, rank, compare within relations, compare between relations, associate, correlate

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W&L 1

• Locate

• Finding something that one knows about already

W&L 2

• Identify

• Describe an object not necessarily known previously

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W&L 3

• Distinguish

• Detecting different values of same variable

W&L 4

• Categorize

• Define divisions that visual objects can be sorted by

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W&L 5

• Cluster

• Determining whether data items are clustered or not

W&L 6

• Distribution

• Describe overall pattern of data

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W&L 7

• Rank

• Finding best and worst, for example

W&L 8

• Compare within entities

• Decide something based on attributes of similar objects

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W&L 9

• Compare between relations

• Different or sets of entities used as basis of comparison

W&L 10

• Associate

• Form relationship between objects on display

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W&L 11

• Correlate

• Determine which objects share similar attributes

Another Taxonomy

• Zhou and Feiner ’98

• Discuss

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Visual Task Taxonomy

• Zhou and Feiner developed a hierarchical taxonomy/model of visual tasks

# Relational tasks Associate -- Collocate -- Connect -- Unite -- Attach Background Categorize -- MarkDistribute Cluster

-- Outline -- Individualize Compare -- Differentiate -- Intersect

Correlate -- Plot

-- MarkCompose Distinguish -- MarkDistribue -- Isolate Emphasize -- Focus -- Isolate -- Reinforce Generalize -- Merge Identify -- Name -- Portray -- Individualize -- Profile

Locate -- Position -- Situate -- Pinpoint -- Outline Rank -- Time Reveal -- Expose -- Itemize -- Specify -- Separate Switch

# Direct visual

# organizing and

# encoding tasks Encode

-- Label -- Symbolize -- -- Quantify -- -- Iconify -- Portray -- Tabulate -- Plot -- Structure -- Trace -- Map

Interpretation

• The nested items are refinements of particular ways of achieving task

• E.g., To locate an item, we might use the more specific visual task pinpoint

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Dimensions

• Visual tasks have two main dimensions

−1. Visual accomplishments - describe

presentation intents that task might help to achieve

−2. Visual implications - particular type of visual action that visual task may carry out

1. Visual Accomplishments

• All about presentation intent

• Classified into two categories:

−Tasks that inform the user (e.g., make a presentation with ppt)

−Tasks that enable user to explore or compute (e.g., decide which stock to buy)

• Each of these can be broken down further

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Visual Accomplishments

Inform Enable

Elaborate Summarize Explore Compute

Search Verify Sum Differentiate Emphasize

Reveal

Associate Background Categorize Cluster Compare Correlate Distinguish Generalize Identify Locate Rank

Correlate Locate Rank Correlate Locate Rank Categorize

Cluster Compare Correlate Distinguish Emphasize Identify Locate Rank Reveal

Categorize Compare Correlate Distinguish Identify Locate Rank Reveal

2. Visual Implications

• Categorize various visual tasks by whether they imply

−Certain types of visual organization

−Certain ways of visual signaling

−Certain paths of visual transformation

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HW 2

• Design a visualization

• Minivan data

• Start now – next class will help some too

Odds-n-Ends

• Questionnaires

• Co-web

• Pictures

• Office hours

• Logo

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Upcoming

• Multivariate Data

−The “DB session”

−Reading:

Chapter 3 Inselberg paper

• Multivariate visualization tools

• Graphical principles

Be reading Tufte

References

• Spence & CMS texts

• All referred to papers