Attention--Selective.

• Limited--not all sensory stimuli simultaneously gets continued processing. Selective--attention must be selective exactly because it is limited.

Properties of Attention

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.

Yum, yum,

beetles. ..

Example of attention to the wrong thing.

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.

+ <

+Random

delay

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 sideinvalid 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 itinvalid 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 muchinvalid 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 wordsthat are written in RED ink, and ignore other words

crownabout

headpaper

aboveslight

herodance

slowlypart

Crime Crown Country

Head Hold Hate

Slight Sold Skin

Peace People Paper

So you can selectively attend to justone 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.

SearchSometimes 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 variedDistractors (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

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╝ ╝

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╝╝

╝╝ ╝☼

☼

☼☼

☼

╝

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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Typical results

Number of stimuli in array0 30

Disjunctive search

Conjunctive search

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ctio

n ti

me

Interpretation

Number of stimuli in array0 30

Disjunctive search--Parallel

Conjunctive search--Serial

Rea

ctio

n ti

me

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)

Aware-ness

Processing physical characteristics (e.g., loudness, pitch)

Processing semantics (i.e., meaning, category membership)

Aware-ness

Processing physical characteristics (e.g., loudness, pitch)

Processing semantics (i.e., meaning, category membership)

Aware-ness

Early filter

Late filter

Method to study early vs late

Attended ear

Unattended ear

Shadowing to ensure attention

“It has often been said

that the early bird catchesthe worm,

however. . .”

“Shell. . Nurse. . .radio”

“It has often been said

that the early bird catches

the worm, however. . .”

Attended ear

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)

Processing semantics (i.e., meaning, category membership)

Aware-ness

Everything, includingunattended ear, is processedfor physical characteristics

Only attended stuff is processedfor 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 earUnattended ear

It works, but only about 1/3 of the time!!

“It has often been said

that the early bird catchesthe worm,

however. . .”

“Shell. . Nurse. . .radio. .

Drew Barrymore, stop shadowing. . .

early bird catchesthe worm, hey I

heard that. . .”

More late filter evidence--Treisman (1960)

Attended earUnattended ear

“If you’re creaming butter and piccolos, clarinets, and tubas seldom play solos.”

“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

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?

The fall reflects weak exports and a

slowing

Wrench. . .Paris. . sofa. . . New York

The fall reflects weak exports and a slowing

Conclude from this study--unattended materialis evaluated for meaning.

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.

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).