Attention
•Part 2
Early Selection Model (Broadbent, 1958)
input
detection
recognition
FILTER
Only information that passed the filter received furtheranalysis (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
Reaction
Time
(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
Reaction
Time
(msec)
“Yes”
“No”
Lab: Voluntary Cueing
Valid Trials
70%
Invalid Trials
15%
Neutral Trials
15%
Voluntary Cueing
•Same result for short andlong cue-to-target delays(short ‘green’, long ‘blue’)
Lab: Automatic Cueing
Cued Trials
??%
+
Miscued Trials
+
Neutral Trials
+
Automatic Cueing
•For short cue-to-target delay(‘green’), same result as forvoluntary cueing (validly cuedfaster than invalidly cued)
•For long cue-target delays, thereverse pattern (inhibition ofreturn)
+
+
Neurological Deficits in Visuo-spatialattention
•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
Right
Left
LVF
RVF
Right
hemisphere
Left
hemisphere
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
Parietal
Cortex
Inferotemporal
Cortex
(Relay Station)
(Detects Edges)
(Color,
Form)
(Shape,
Object
Recognition)
(Location,
How to reach or
act 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)
Signal
Analysis
Receptive Field
Attention Effects in
Single Neuron Responses
100 msec
Frequency
of
spikes
Attended bar
Unattended bar
(Robert Desimone, NIH)
Retina
LGN
V1
V4
Parietal
Cortex
Inferotemporal
Cortex
(Relay Station)
(Detects Edges)
(Color,
Form)
(Shape,
Object
Recognition)
(Location,
How to reach or
act upon)
Attention
Effects
Here
No
Attention
Effects
Here
Early visual processing IS affected byselective attention.
This is a challenge for a pure late selectionmodel.
BUT, it does not mean that late selection isnot occurring.
Conclusions fromNeuroscientific Evidence:
Automatic vs. Voluntary Priming
+AA
Warning
signal
Test
signal
neutral
(Posner & Snyder, 1975)
S
KK
15%
P
PP
S
KK
G
GG
15%
70%
“No need to think of P”
Automatic Priming
“think of P! yeah baby!”
Automatic Priming
Voluntary Priming
Often misleading
G
GG
70%
Often predictive
Difference
between
experimental
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 Priming
Benefit with cost
Automatic vs Voluntary priming (part 2)Neely (1977)
•If you see a body part as a Prime, expect a building partas a target. For example,
–Body -> door
•some pairs were semantically related, but unexpected
– body -> heart
Priming Results
•Blue: Expected pair
– Body -> door
– voluntary priming
–Evolves with time
•Green: Related but unexpected
–Body -> heart
– automatic priming, followedby a cost from voluntarypriming
Cue-target delay (ms)
Cost facilitation (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 tohandle different tasks or stimuli at once--dividedattention.
3. Sustained mental effort: limited ability toengage in protracted thought, especially on thesame subject--vigilance.
3 meanings of the word ‘Attention’
P
S
B
O
N
K
G
#
#
#
#
#
#
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 into
Working 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 tothe context word or not (e.g., sugar, shoes)
•When subjects fail to report T2, look at their brainwaves (ERPs) to assess whether the meaning ofthat 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…