Transcript Overview and Detail

Cognitive Issues &
Human Tasks
CS 7450 - Information Visualization
January 18, 2005
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
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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
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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
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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
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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
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Navigation
Content
Model
Browse
Browsing
strategy
Formulate a
browsing
strategy
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Internal
model
Interpretation
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Interpret
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Interpretation
• Can someone explain that?
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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 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 action
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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
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Process
task
Raw
data
Data
tables
Data
transformations
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Visual
Structures
Visual
mappings
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Views
View
transformations
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Knowledge Crystallization
Overview
Zoom
Filter
Details-on-demand
Browse
Search query
Task
Author,
decide
or act
Forage
for data
Search for
schema
Reorder
Cluster
Class
Average
Promote
Detect pattern
Abstract
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Extract
Compose
Problem-solve
Instantiate
schema
Instantiate
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Read fact
Read comparison
Read pattern
Manipulate
Create
Delete
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Intermission
• Popcorn & sodas for everyone!
• Admin stuff
 Circulate photos
 Anyone need an info form yet?
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2. User Tasks
• What things will people want to
accomplish using information
visualizations?
• Last time, we discussed
 search vs. browsing
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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
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Lin ‘97
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Thought
• Maybe infovis isn’t about answering
questions or solving problems… hmmm
• Maybe it’s about asking better questions
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Tasks
• OK, but browsing and search are very
high level
• Let’s be more specific…
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Example from Last Time
Questions:
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Which state has the highest income?
Is there a relationship between income and education?
Are there any outliers?
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Example courtesy
of Chris North
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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
 ...
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Shneiderman
• What’s his mantra?
 Overview first,
on demand
 Overview first,
on demand
 Overview first,
on demand
 Overview first,
on demand
…
then zoom & filter, then details
then zoom & filter, then details
then zoom & filter, then details
then zoom & filter, then details
VL ‘96
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Elaborated More
• Task set?
 Overview
 Zoom
 Filter
 Details on demand
 Relate
 History
 Extract
• Are these end-user tasks?
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User Tasks
• Wehrend & Lewis 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
Vis ‘90
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W&L 1
• Locate
• Finding something that one knows about
already
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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
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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
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W&L 6
• Distribution
• Describe overall pattern of data
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W&L 7
• Rank
• Finding best and worst, for example
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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
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W&L 10
• Associate
• Form relationship between objects on
display
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W&L 11
• Correlate
• Determine which objects share similar
attributes
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Another Taxonomy
• Zhou and Feiner
• More for multimedia explanation than for
infovis, but still useful to us
CHI ‘98
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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
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Correlate
-- Plot
-- MarkCompose
Distinguish
-- MarkDistribue
-- Isolate
Emphasize
-- Focus
-- Isolate
-- Reinforce
Generalize
-- Merge
Identify
-- Name
-- Portray
-- Individualize
-- Profile
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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
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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
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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
Elaborate Summarize
Emphasize
Reveal
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Associate
Background
Categorize
Cluster
Compare
Correlate
Distinguish
Generalize
Identify
Locate
Rank
Enable
Explore
Search
Categorize
Cluster
Compare
Correlate
Distinguish
Emphasize
Identify
Locate
Rank
Reveal
Verify
Compute
Sum
Categorize Correlate
Compare
Locate
Correlate
Rank
Distinguish
Identify
Locate
Rank
Reveal
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Differentiate
Correlate
Locate
Rank
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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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Making InfoVis More Task-Focused
• InfoVis
 Representational Primacy
Show the data truthfully in meaningful ways
 Analytic Primacy
Support user analysis and tasks
Amar & Stasko
InfoVis ‘04
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User Tasks
• Examples of “higher-level” tasks
 Complex decision making, especially under
uncertainty
 Learning a domain
 Identifying the nature of trends
 Predicting the future
…
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Closing the Gaps
Narrowing the gaps between representation and analysis
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Narrowing Methods
•
Knowledge Precepts (for design and
evaluation)
 Worldview Gap
1. Determine domain parameters
2. Expose multivariate explanation
3. Facilitate hypothesis testing
 Rationale Gap
1. Expose uncertainty
2. Concretize relationships
3. Expose cause and effect
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Visual Analytics
• Formation of abstract visual metaphors in
combination with human information
discourse (interaction) that enables
detection of the expected and discovery of
the unexpected within massive,
dynamically changing information spaces
 Intelligence analysis
 Bioinformatics
 Financial analysis
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Wong & Thomas
IEEE CG&A, ‘04
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NVAC
• National Center formed by Dept. of
Homeland Security to assist with
intelligence analysis, emergency response,
border patrol, etc.
• Blending cognitive analyses, hypothesis
testing with visualization to develop better
techniques and systems
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HW 1
• Example due Thursday
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HW 2
• Turn in today
• Challenging?
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HW 3
• Given set of incomplete, missing and
inconsistent facts
• Develop hypothesis for what is planned to
occur
• Turn-in
 Hypothesis (paragraph)
 The visual aids you created, if any
• Due next Tuesday
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Odds-n-Ends
• Co-web
• Office hours
• Logo
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Upcoming
• Multivariate Data
Be reading
Tufte
 The “DB session”
 Reading:
Chapter 3
Inselberg paper
• Multivariate visualization tools
• Graphical principles
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References
• Spence & CMS texts
• All referred to papers
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