Attention--Selective.
Properties of Attention
• Limited--not all sensory stimuli
simultaneously gets continued processing.
Selective--attention must be selective
exactly because it is limited.
What is the point of selectivity?
1. Given that attention is limited, it must be
selective, meaning you’re not always
attending to the right thing.
Example of attention to the wrong
thing.
Yum,
yum,
beetles. ..
If attention can be on the wrong
thing. . .
Sometimes you must switch
Sometimes you must search
Always you must evaluate
Switch
How do we switch?
Posner’s beam metaphor
Attention is like a “spotlight” that enhances perceptual
processing.
This turns out to be a useful metaphor that is partly right,
but not completely.
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Random
delay
<
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Results
1. When the cue is valid, RTs are fast
2. When the cue is invalid, RTs are slow
Neural basis of the beam
• Neural evidence shows that damage to
different parts of the brain support three
separate processes: disengage, move, and
engage
If disengage is damaged
(posterior parietal cortex). . .
valid trials= ok on either side
invalid trials= bad on contralateral side bes. it's difficult to
disengage attention from the invalid side
If move is damaged (superior colliculus)
valid trials= very slow to show
advantage of the cue, but do show it
invalid trials= slow but not a special
problem--at short delays cue is not
used
If engage is damaged (thalamus)
valid trials= don't seem to use
the cue much
invalid trials= don't seem to use
the cue much. Easily distracted
by irrelevant stimuli.
Thus the beam metaphor works,
BUT
• A couple of predictions of the beam
. metaphor don’t work
• Moving attention greater distances doesn’t
take a longer time (Kwak et al, 1991)
• Moving attention isn’t slowed down by
intervening stuff (Sperling & Weichselgartner,
1995).
• Beam implies attention selects space.
In the following slides, try to remember the words
that are written in RED ink, and ignore other words
crown
about
paper
head
above
slight
dance
hero
slowly
part
Crime Crown Country
Head Hold Hate
Slight Sold Skin
Peace People Paper
So you can selectively attend to just
one word, based on color, even though
another word overlaps in space
Implication: when you switch, you are switching not to
a location in space, but to another object or object part.
Search
Sometimes you know what
you want to attend to, but
you’re not currently
attending to it, so you need to
redirect attention to the
appropriate target.
In the next slide, find Waldo
In the next stimulus array, search for the
red target
And again, find Waldo
Still pretty easy even with more varied
Distractors (still search for red circle)
This sort of search works with
attributes other than color, too.
In the next array, look for the
circle.
Again, look for the circle
╝ ╝
╝
☼
╝ ╝☼
☼
╝
☼
☼
☼
╝
╝
╝
But watch what happens when you search an array
in which the target is NOT defined by a single
feature.
Look for the red circle But there will be non-red
circles and red non-circles.
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╝
Reaction time
Typical results
Conjunctive
search
Disjunctive
search
0
30
Number of stimuli in array
Reaction time
Interpretation
Conjunctive
search-Serial
Disjunctive
search-Parallel
0
30
Number of stimuli in array
Evaluate
Because attention is selective, you must
always be evaluating other stimuli to
see if they are more important than
what you’re attending to now.
How does this processing work?
Processing
physical
characteristics
(e.g., loudness,
pitch)
Processing
semantics (i.e.,
meaning,
category
membership)
Awareness
Early filter
Processing
physical
characteristics
(e.g., loudness,
pitch)
Processing
semantics (i.e.,
meaning,
category
membership)
Awareness
Late filter
Processing
physical
characteristics
(e.g., loudness,
pitch)
Processing
semantics (i.e.,
meaning,
category
membership)
Awareness
Method to study early vs late
Attended ear
Unattended ear
“It has often
Attended
ear
been said
that the early
bird catches
the worm,
however. . .”
“Shell. . Nurse.
. .radio”
“It has often been said
that the early bird
catches
the worm, however. .
.”
Shadowing to ensure attention
Early Results from Cherry
• People don’t remember words from
unshadowed ear
• People don’t notice if speech is played
backwards, or if language changes
• People do notice if a pure tone is played, or
if there is a gap
• Conclude--early filter
Why early?
Processing
physical
characteristics
(e.g., loudness,
pitch)
Everything, including
unattended ear, is processed
for physical characteristics
Processing
semantics (i.e.,
meaning,
category
membership)
Awareness
Only attended stuff is processed
for semantics (meaning)
Early filter?
But can’t you sometimes pick up unattended
information based on its content?
Suppose you’re at a party and talking to
someone, with many conversations around you.
What might someone in another conversation
say that you would attend to?
Cocktail party phenomenon
Attended ear
“It has often
been said
that the early
bird catches
the worm,
however. . .”
Unattended ear
“Shell. . Nurse. .
.radio. . Drew
Barrymore, stop
shadowing. . .
early bird catches
the worm, hey I heard
that. . .”
It works, but only about 1/3 of the time!!
More late filter evidence-Treisman (1960)
Attended ear
“If you’re creaming
butter and piccolos,
clarinets, and tubas
seldom play solos.”
Unattended ear
“Many orchestral
instruments, for
example, sugar,
it’s a good idea
to use a low
mixer speed.”
“If you’re creaming butter
and sugar, it’s a good. . .uh.
..seldom play solos.
Indirect measures--Corteen &
Wood (1974): Phase 1
Phase 1: Shock
associated with
three city names
(e.g., Dallas, Fresno,
New York).
Ow.
Wrench. .
.Sofa. . . New
York
Train until GSR response
The fall reflects
weak exports
and a slowing
Wrench. .
.Paris. . sofa. . .
New York
The fall
reflects weak
exports and a
slowing
Phase 2: Dichotic listening: they shadow an irrelevant
message from one ear. The other ear gets words, plus
occasional city names. Do they show GSR to the three
city names, and even to new city names?
Participants showed the GSR response
38% of the time to the old city names,
23% of the time to new city names, and
just 10% of the time to new nouns.
Conclude from this study--unattended material
is evaluated for meaning.
Later filter theories.
These results led some researchers to
propose that all stimuli are evaluated
for their semantic content as well as
their physical properties.
Which is right?
In some studies, early filter seems right
(as when people can’t report anything
from the unattended ear)
In other studies, they sometimes get
their name, they show some effect in the
GSR study.
Early filter looks right.
In the studies where people seem to get
semantic information, it looks likely that
they are actually rapidly switching
attention to the ear they are supposed to be
ignoring. When you do the experiments
more carefully to guard against this, it
looks like they don’t get much information
from the unattended ear.
Mechanism of selection is not
completely worked out, of course; but,
people do seem to be quite good at
selecting objects for attention based on
individual features (such as color).