Attention

Looking without Seeing

Why Have Attention?

• Limited resources– Too much information

• Attention:1. selects important/relevant information

2. modulates it in the context of the task at hand

Attention Mechanisms

• Top-Down– Goal-driven

• Bottom-up– Stimulus-driven (“attention capture”)– There is debate if total bottom-up really exists

• Attention capture is shown to be modulated by task goals

• Early Selection vs. Late Selection

Visual AttentionVisual Attention

© Stephen E. Palmer, 2002

Evidence for Early Selection in Audition

Shadowing paradigm

What can be followed?

Position (left/right)?

Pitch (male/female)?

Language (English/French)?

15.1

++X

--> Early Selection

Visual AttentionVisual Attention

© Stephen E. Palmer, 2002

Evidence for Late Selection in Audition

Cocktail Party phenomenon

Unselected information can get in:

Subject’s own name

Words expected from context

--> Early and late selection

15.1

Visual AttentionVisual Attention

© Stephen E. Palmer, 2002

Inattention Paradigm (Mack & Rock)

What do we see without attention?

15.1

A. Trials 1-3

B. Inattention Trial

C. Recognition Test

D. Divided Attention Trial

Visual AttentionVisual Attention

© Stephen E. Palmer, 2002

Inattention Paradigm Results:

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100

80

60

40

20

0

Pe

rfo

rma

nce

re

lativ

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Ch

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Inattention Divided Control

Trial Condition

ChancePerformance

Shape

Number

Color

Location

PerfectPerformance

Visual AttentionVisual Attention

© Stephen E. Palmer, 2002

Inattentional Blindness:

15.1

On many trials, subjects

report seeing NOTHING if

the test object is at fixation.

Square at Fixation: 50-75% IB

Own Name at Fixation: 5% IB

Other’s name at Fixation: 35% IB

Variant of own name at Fixation: 60% IB

(e.g., JECK instead of JACK)

Show movie…

Visual AttentionVisual Attention

© Stephen E. Palmer, 2002

Change Blindness

15.1

Visual AttentionVisual Attention

© Stephen E. Palmer, 2002

Change Blindness

15.1

Eye Movements

Q: Why? A: Limitations of the eye – only fovea is high-res

enough for many tasks

Two types:– Saccades

• Rapid motion (25-30 ms) between fixations• Saccades occur every 250-300 ms• Also evidence for “micro-saccades”

– Smooth-pursuit (tracking) movements• Require feedback

Eye-Tracking

Alfred Yarbus

goal-attenuated

Alfred Yarbus

Saliency Maps

• Itti et al proposed that bottom-up attention can be predicted from low-level visual features.

• Eye-tracking can be used to validate the predictions

• What are the problems with this idea?