Week 7: Attention in Space and Time

Question 1

what are the Psychological Function of Spatial Attention? (2)

Answer 1

 To assign limited-capacity processing resources to relevant stimuli in environment

 Must locate stimuli among distractors and process (identify) them

Question 2

Visual Search: Finding relevant stimuli among distractors:
Char
Objective

Answer 2

Display of no. of letters:
1) small display
2) large display
Identify a letter: is M present in the display.

Objective:
DV: RT of finding the letter
IV: Display size
Measure mean RT as a func of display size

Question 3

Effects that account for easy VS difficult search tasks.

Answer 3

Pop-out effects:

Colour, orientations and form

Question 4

Task 1:
Parallel Search for Feature Targets: Experiment and outcome
(Ed for Parallel Search)

Answer 4

Given an target to search
(vertical bar/red bar)
Look at display and respond yes or no to the presence of target.

Findings:
Mean RT doesn’t increase with display size (gradient = 0, amount of lines) for both presence/absence of target

Suggest:
We are able to compare contents of each display location with mental representation of target at the same time – parallel search.
Thus unaffected by amount of display.

Question 5

Task 2:
Conjunction Targets Do Not Pop Out: Experiment and outcome
(Ed for Serial Search)

Answer 5

Target defined by combination of colour and orientation (with similar (1 aspect) as distractor; S11)

Findings:
RT increases linearly with display size -> we have to search for the through the display
Slope twice as steep for target absent as target present trials

Suggest:

1) Need to focus attention on target to detect it – focus attention on each item (color/orientation) in turn.
2) Constant scanning rate predicts linear RT/display size function
3) Stop when target is found
4) On average, search half the display on target-present trials, all of the display on target-absent trials
5) Constant scanning rate predicts 2:1 slope ratio

Question 6

Task 3:

Pop-Out Effects With Letter Stimuli (properties)

Answer 6

1) Pop out when targets can be identified by a single features (straight lines among curves or vice versa) T among C & S
2) No pop out when targets can’t be identified by a single feature (straight lines among straight lines or curves among curves) T among L and F
* Although target stimuli compose of multiple features, one can identify them via a unique feature (straight among curves)

Question 7

Feature Integration Theory
(Treisman & Gelade, 1980)
claims:
(S15)

Answer 7

1) Role of spatial attention is to bind features into perceptual compounds (a whole)
2) Each feature registered in its own feature map
3) Without attention features are free-floating, may lead to illusory conjunctions

Question 8

Feature Integration Theory
(Treisman & Gelade, 1980)
Explanation of Parallel vs Serial Search

Answer 8

1) Parallel search
there is red map (1 feature). Therefore, we only need retinal image (no need to bind features) -> fast.

2) Serial Search
need additional step (spatial attention: to shine the spotlight on the stimulus) need to bring the maps together.

Question 9

Feature Integration Theory:
Experiment:
Feature VS Conjunction Search

Answer 9

1) Conjunction targets require feature binding, so need focused attention – leads to serial search (linear increase)
2) Feature targets don’t require feature binding, don’t need focused attention – leads to parallel search (almost flat line for absent and present trials)

Question 10

Feature Integration Theory:

Problems (limitations and faults)

Answer 10

1) Pop out sometimes depends on complex (compound or conjunction) object properties, not just simple features (Enns & Rensink, 1990)
a) rebuttals -> they create a new feature (depth) maybe tts y its can be identified.

2) High-level, not low-level properties predict pop out.

3) even in the original paper, the so called straight line may not be as linear as they would think.
Inconsistent with idea that pop out only occurs at level of simple features

Question 11

Feature Integration Theory:
Problems (limitations and faults)
Efficient vs. Inefficient Search

Answer 11

Efficient vs. Inefficient Search:
1) Many tasks show intermediate pattern, don’t provide clear evidence of either serial or parallel search (between serial/parallel)

2) Wolfe: better described as inefficient or efficient search
3) No evidence of dichotomous population of search slopes; parallel and serial functions look like ends of continuum

Question 12

Another Theory:
Guided Search Theory (Wolfe, 1989)
Description (S19)

Answer 12

1) Two-stage theory
2) Initial parallel stage provides a candidate list of possible targets
3) Second serial stage checks candidate list for targets
4) Search efficiency depends on similarity of target and distractors
5) Similar targets and distractors lead to large candidate list -> inefficient search
6) Dissimilar targets and distractors lead to small candidate list -> efficient search

*similar to eye movement and suggests:
Pre attentive processing -> stimulation tat can be extracted pre attentively to guide our attention.

Question 13

Gaps/Failures of Visual Spatial Attentions:

Failures of Focused Attention

Answer 13

1) Visual search looks at costs of divided (distributed) attention: performance decline with increasing display size is evidence of capacity limitations
2) Some situations where there is a benefit not to divide attention: avoid processing distractor stimuli
3) Limitations of focused attention and involuntary processing of irrelevant stimuli

Question 14

Failures of Focused attention:

The Stroop Effect (Stroop, 1935)

Answer 14

Name the colour of the ink in which the word is written; measure RT

fastest (compatible: red for ink n word)
Intermediate (neutral: word not related to color)
Slow (incompatible: dif color meaning for word n color)
failure of our attention, inhibiting the conflict between the given info.

Question 15

The Stroop Effect (Stroop, 1935):

Parallel processing of colour naming and word reading: incompatible

Answer 15

1) Word reading: “fast and automatic”
2) Colour naming: “slow and controlled”
creates output interference
=> reason its hard: the fast one is the irrelavent one

Asymmetrical: no interference of ink colour on word naming

Question 16

What makes a process automatic?

Answer 16

Fast, parallel, effortless, doesn’t require capacity
( Learned S-R associations)

Automaticity basis for skill acquisition (reading, driving, playing a musical instrument, etc.)
Is practice enough?

Question 17

Controlled and Automatic Processing:
Shiffrin & Schneider (1977)
=> practice is not enough
Details
S25

Answer 17

1) Search for digit targets in arrays of distractor letters in rapid sequences (or vice versa)
2) Vary size of target (memory) set: 1-4 items => difficulty

3)Vary size of stimulus displays: 1-4 items
(Masking stimuli, very fast)

4) Consistent mapping (CM): target and distractor sets were distinct (always digits or numbers as targets)
5) Varied mapping (VM): targets on some trials were distractors on others

Question 18

Controlled and Automatic Processing:
Shiffrin & Schneider (1977)
results
did the task become automatic?

Answer 18

1) Performance under CM became automatic with practice (>90%)
2) Became independent of memory set and display size
3) Subjectively effortless, spontaneous pop-out of targets from text
4) Never became automatic under VM
5) Requires consistency of target set membership
6) Consistent with capacity-free, effortless encoding account

Question 19

The Eriksen Flanker Task
congruent vs incongruent tasks
rationale and procedures.

Answer 19

Is the central character an E or an F? – measure RT

RT(compatible) < RT(neutral) < RT(incompatible)

Involuntary processing of flankers (side letters) even when attempting to ignore them

Question 20

The Eriksen Flanker Task
congruent vs incongruent tasks
results, significants

Answer 20

Implies some parallel processing of conjunction stimuli (similar features)

Failure of focused attention (even through we know where to focus, we still process the irrelavent ones)

Decreases with spatial separation, disappears at 1-1.5 degrees

Provides estimate of size of focus of attention (“spotlight” and central vision (?) are well matched)

Stimuli falling within spotlight processed automatically

Question 21

Attention in Time: The Attentional Blink

Defination and Precedure

Answer 21

Attentional Blink: the 2nd target cannot be detected or identified when it appears close in time to the first.

 Rapid serial visual presentation (RSVP) task
 100 ms exposure per item; each item masked by following item
 Two targets: report the white letter, detect whether there was an “X” present

Question 22

Attention in Time: The Attentional Blink (AB)
Findings
s30,31

Answer 22

Plot second target (T2) performance as a function of the time (lag) since the first target (T1)

T2 performance declines (lowest @ position 3) and then recovers (7)– “attentional blink”

 Only find it if T1 is processed; if T1 ignored no AB

 Depends on T1 processing

 Worst performance not immediately after T1 but some time later (Lag 1 sparing)

AB Effect takes time to build up, but relatively long lasting (up to 600 ms)

Question 23

Where is the Attentional Bottleneck?

1) Translating perception into action od stimuli

Answer 23

Must distinguish relevant from irrelevant stimuli

Good at monitoring for relevant stimuli, rejecting irrelevant stimuli preattentatively if they are not perceptually confusable

Forming representations of relevant stimuli and making decisions about them makes us insensitive to new stimuli for 500-1000 ms (double-target deficit, AB)

limitation between processes intervening betw the stimulus and response

Question 24

Single-channel theory (Welford, 1959)

Answer 24

Can only make one decision at a time

Single-channel theory suggest that brain’s information processing system has a filter that is used to take in necessary information and block out the rest.