Attention

• Part 2

Early Selection Model (Broadbent, 1958)

input detection recognition

FILTER

Only information that passed the filter received further analysis (e.g. meaning).

Late Selection Theory(Deutsch & Deutsch, Norman)

input detection recognition

FILTER

Early Attenuation Model (Treisman)

input detection recognition

FILTER

Lab: Feature Search

Parallel processing of simple visual features (e.g., color).

Typical Results for “Feature Search”

# of items in display

6 10 20 30

ReactionTime(msec)

“Yes”

“No”

Conjunction Search

• Combination of features (e.g., red AND horizontal)

• Spatial arrangements of features (e.g. black above white)

When targets are defined by:

Lab: Conjunction Search

‘Find the blue square’

Lab: Conjunction Search

Treisman’s Results for “Conjunction Search”

# of items in display

2 4 6 10 20 30

ReactionTime(msec)

“Yes”

“No”

Lab: Voluntary Cueing

Valid Trials70%

Invalid Trials15%

Neutral Trials15%

Voluntary Cueing

250

270

290

310

330

350

Valid Neutral Invalid

• Same result for short and long cue-to-target delays (short ‘green’, long ‘blue’)

Lab: Automatic Cueing

Cued Trials??%

+

Miscued Trials

+

Neutral Trials

+

Automatic Cueing

250

270

290

310

330

350

Cued Neutral Invalid

• For short cue-to-target delay (‘green’), same result as for voluntary cueing (validly cued faster than invalidly cued)

• For long cue-target delays, the reverse pattern (inhibition of return)

+ +

Neurological Deficits in Visuo-spatial attention

• Hemi-spatial Neglect• lesion in right temporo-parietal junction

• Inability to – attend to the left side of visual space, and thus to– be aware of visual stimulus in the left visual field– Represent spatial relations.

Line-bisection task

RightLeft

LVF RVF

Righthemisphere

Lefthemisphere

LVF RVF

To study the neural substrate of visuo-Spatial Attention, we need

• A patient group: – Hemispatial neglect

• A simple method: – Spatial Cueing

• A cognitive theory: – Posner’s three stage model

• Disengage: – stop attending to what is currently being attended

• Move: – refocus spotlight on new location

• Engage: – begin attending to new stimulus

Spatial Cueing

Cued Trials

+

Miscued Trials

+

Retina

LGN

V1

V4 ParietalCortex

InferotemporalCortex

(Relay Station)

(Detects Edges)

(Color,Form)

(Shape,Object Recognition)

(Location,How to reach oract upon)

Which part of the brain is the source of attention?Where does attention have its effects?

time

Memory/Attention Task(fMRI / ERP)

Regions of Interest

RVF LVF

Stim 1 Stim 2

Single-Unit Recording

“spike” = single neuron’s action potential

(Macaque monkey)

SignalAnalysis

Receptive Field

Attention Effects inSingle Neuron Responses

100 msec

Frequencyofspikes

Attended bar

Unattended bar

(Robert Desimone, NIH)

Retina

LGN

V1

V4 ParietalCortex

InferotemporalCortex

(Relay Station)

(Detects Edges)

(Color,Form)

(Shape,Object Recognition)

(Location,How to reach oract upon)

AttentionEffectsHere

NoAttentionEffectsHere

Early visual processing IS affected by selective attention.

This is a challenge for a pure late selection model.

BUT, it does not mean that late selection is not occurring.

Conclusions from Neuroscientific Evidence:

Automatic vs. Voluntary Priming

+ AA

Warningsignal

Testsignal

neutral

(Posner & Snyder, 1975)

S KK15%

P PP

S KK

G GG15%

70%

“No need to think of P”

Automatic Priming

“think of P! yeah baby!”

Automatic Priming

Voluntary Priming

Often misleading

G GG70%

Often predictive

Differencebetweenexperimental and neutral conditions

faster

slower

15% primed

70%misled

70%primed

15%misled

Low validity(often misled)

High validity

P -> P

P ->G

P ->G

P ->P

Automatic Priming;Benefit without a cost

Voluntary PrimingBenefit with cost

Automatic vs Voluntary priming (part 2) Neely (1977)

• If you see a body part as a Prime, expect a building part as a target. For example, – Body -> door

• some pairs were semantically related, but unexpected– body -> heart

Priming Results

-80

-60

-40

-20

0

20

40

60

200 700 2000

• Blue: Expected pair– Body -> door– voluntary priming – Evolves with time

• Green: Related but unexpected– Body -> heart– automatic priming, followed

by a cost from voluntary priming Cue-target delay (ms)

Cos

t f

acil

itat

ion

(ms)

Question

• Predict pattern of performance when:– the delay between cue and target is very short, – the cue-target delay is longer

– For automatic priming– For voluntary priming

1. Selectivity: only aware of a subset of stimuli--selective attention.

2. Capacity Limitations: limited ability to handle different tasks or stimuli at once--divided attention.

3. Sustained mental effort: limited ability to engage in protracted thought, especially on the same subject--vigilance.

3 meanings of the word ‘Attention’

PSBONKG######

Attentional Blink

You will see a stream of letters rapidly presented in the center Group 1: memorize any vowels Group 2: memorize any vowels and red letters

Target 2

S

N

O

B Target 1 Encoding intoWorking Memory

Attentional Blink: Early or Late Selection?

• Instead of letters, use words.• An initial word establishes context (e.g., milk)• Target 2 is a word that is semantically related to

the context word or not (e.g., sugar, shoes)• When subjects fail to report T2, look at their brain

waves (ERPs) to assess whether the meaning of that target has been processed or not

• N 400 (ERP marker of semantic processing)

Spotlight metaphor

- metaphors are not right or wrong, they are useful or not…