Feature Level Processing

Lessons from low-level vision Applications in Highlighting Icon (symbol) design Glyph design

Spotfire product

Visual symbols

Architecture for visual thinking

Primitives of Perception (the phonemes).

The whole visual field is processed in parallel

This machinery tells us what kinds of information are easily distinguished

Popout effects (general attention) Segmentation effects (dividing up the

visual field)

Segmentation by Primitive Features

Livingston and Hubel

Neural Architecture

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formcolor

12&34A4B

56

4C

Visual Area 1 (Primary Visual Cortex)

formstereo

stereo

stereo

form

form

MT movement/stereo

Visual Area 2movement

color

color

colorform

form

movement

Orientation and Size(Gabor primitives)

Image segmentation based on texture

ResultingSegmentation

Vertical fat Gaborfilters respond moststrongly

Horizontal skinnyGabor filters respondmost strongly

Vector fields like using gabors

Pre-Attentive Processing

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Color is Pre-Attentive (Pops out)

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Generic Pre-Attentive Experiment

a

3 6 12

Number of distractors

500

700

900 Number of irrelevant items varies

Pre-attentive 10 msec per item or better.

Color

Orientation

Motion

Size

Simple shading

Conjunction (does not pop out)

Semantic Depth of Field

Compound features (do not pop out)

Surrounded colors do not pop out

Laws of pre attentive display

Must stand out on some simple dimension color, simple shape = orientation, size motion, depth

Lessons for highlighting – one of each

Blinking momentarily attracts attention

Lessons: Highlighting how to make information available to attention

A flying box leads attention

Using colorUsing underlining

Blinking momentarily attracts attention

Motion elicits an orienting response

More Pre-Attentive

Conjunction (does not pop out)

Pre-attentive conjunction

Conjunctions of motion and shape do pop out. (color also?)

McLeod, P., Driver, J. and Crisp, J. (1988) Visual search for a conjunction of movement and form is parallel. Nature 332, 154-155.

Driver, J., MacLeod, P. and Dienes, Z. (1992) Motion coherence and conjunction search: Implications for guided search theory. Perception and Psychophysics. 51, 1, 79-85.

MEGraph: Experimental system

Allows for various topological range highlighting methods

Goal from 30 to 2000 nodes

MEGraph

Pre-Attentive Channels

Form (orientation/size) Color Simple motion/blinking Addition/numerosity (up to 3) Spatial, stereo depth, shading, position

Pre-Attentive Conjunctions

Stereo and color Color and motion Color and position Shape and position

In general: spatial location and some aspect of form

Pre-Attentive Lessons

Rapid visual search (10 msec/item) Easy to attend to Makes symbols distinct Based on simple visual attributes Faces, etc are not pre-attentive

Designing symbols

Perceptual Channels

Color (3) Shape (size, orient) Motion (2?) Texture (2++) Position (x,y)

Spatial Channels

Like interferes with like

Size contrast effect

Orient contrast

Size contrast effects can cause errors in information display

Chris Weigle: orientation channels for info display

Mapping data to display variablesData glyphs

Position (2) Orientation (1) Size (spatial frequency) Motion (2)++ Blinking? Color (3)

Note we have the problem of heterogeneity – There is no good solution

Star glyphMethod

Starplot glyph

Spotfire product

Integral and Separable dimension (Garner)

Can we read display attributes Independently Holistically

Speeded classification task. Sort into two piles on one dimension or another

Separable

Integral

Motion Color

red-green yellow-blue

black-white red-green

x-size y-size

Color orientation

Lessons for Information Display

Orthogonality - use a different channel for a different type of information

If you need this use separable challenge

If you need to highlight by two properties use separable dimensions.

The programmable filter

We can only look for patterns of simple features Conjunctions of shape, color cannot be

programmed for parallel search of field Conjunctions of depth/motion and color/shape can

be

Integral dimensions tend to be seen holistically cannot be separated

Separable dimensions tend to be seen separately

Searchlight Model of Attention

a

VisualSearch orMonitoringStrategy

EyeMovementControl

Useful VisualField of View

Searchlight Properties

Size varies with data density Size varies with stress level Attention operators work within the

searchlight beam Attention is a tunable filter

Eye movements 3/sec – A series of saccades