Lecture 4: Attention in Space and Time

Question 1

Question

Answer 1

Answer

Question 2

What is the Psychological Function of Spatial Attention?

Answer 2

> To assign limited-capacity processing resources to relevant stimuli in environment
Must locate stimuli among distractors and process (identify) them

Question 3

What is visual search?

Answer 3

> Laboratory analogue of cheetahs-in-the-savannah (how attention works)
target stimuli embedded in distractors - is the target present
Measure mean RT as a function of display size

Question 4

How do search tasks differ in difficulty?

Answer 4

Some search targets seem to “pop out” from the background (effortless); others require attention

Question 5

Why are letter stimuli used in visual search?

Answer 5

> simple
easy to present
easy to control
allows to quantify the size and difficulty of search task (count number of targets vs. distractors)

Question 6

What cause pop-out effects? How is it searched?

Answer 6

> Simple features: Unique colours and unique orientations both pop out

Question 7

What happens with visual search in pop-out task?

Answer 7

> Mean RT doesn’t increase with display size
Compare contents of (a) each display location with (b) mental representation of target at the SAME time– parallel search

Question 8

What are conjunction target? How is it searched?

Answer 8

> Does not pop out - requires attention
Target defined by combination of colour AND orientation (both colour and orientation in the distractors as well)
RT increases LINEARLY with display size (add more items)
Slope TWICE as steep for target ABSENT as target PRESENT trials = SERIAL search (search is self-terminating (on avg. search half the display), on present trails have to go to end = exhaustive search)
…Constant scanning rate predicts 2:1 slope ratio
need to compare mental representation of the target each display location IN TURN
Seem to need to focus attention on target to detect it – focus attention on each item in turn
Constant scanning rate predicts linear RT/display size function

Question 9

How else can you get pop-out effects?

Answer 9

> Pop out when targets can be identified by a single features (straight lines among curves or vice versa)
No pop out when targets can’t be identified by a single feature (straight lines among straight lines or curves among curves)

Question 10

What is feature integration theory?

Answer 10

(Treisman & Gelade, 1980)
> Theory of visual search
> Role of attention is to bind perceptual features into coherent perceptual objects (compounds) and the location
> Visual stimuli projected on the retina which consists of a number of properties such as lines and colours - they are coded independently by PARALLEL neural systems
> Each feature (lines, colours etc.) registered in its own separate feature map - the contents of maps are not related together
> Attention brings together these maps (e.g. red and horizontal)
> Without attention features are free-floating, may lead to ILLUSORY CONJUNCTIONS

Question 11

What does Feature Integration theory predict about single feature targets?

Answer 11

> Single feature targets don’t require feature binding, don’t need focused attention – leads to parallel search

Question 12

What does Feature Integration theory predict about Conjunction targets?

Answer 12

> Conjunction targets require feature binding, so need focused attention – leads to serial search
get linear increase as function of display size and 2:1 ratio

Question 13

What are Problems With FIT?

Answer 13

> Pop out sometimes depends on complex object properties, not just simple features (Enns & Rensink, 1990) e.g. 3D effect but orientation may be a simple feature in itself
High-level, not low-level properties predict pop out.
Inconsistent with idea that pop out only occurs at level of simple features
Main Criticism: Many tasks show intermediate pattern, don’t provide clear evidence of either serial or parallel search

Question 14

What did Wolfe say re FIT?

Answer 14

> Many tasks show intermediate pattern, don’t provide clear evidence of either serial or parallel search
Not a linear function (RT vs display size) —> it curves over (therefore cost of RT diminishes as you add distractors)
Many search show a slight increase rather than being completely flat as predicted by parallel search
Wolfe: better described as inefficient or efficient search
No evidence of dichotomous population of search slopes; parallel and serial functions look like ends of continuum

Question 15

What is Guided Search Theory?

Answer 15

(Wolfe, 1989)
> Two-stage theory
> Initial PARALLEL stage which doesn’t identify target but provides a candidate list of possible targets
> Second SERIAL stage checks candidate list for targets
> Search efficiency depends on similarity of target and distractors (time taken for both of these stages)
> Similar targets and distractors lead to large candidate list and inefficient search (get curved graph because not everything goes in candidate list)
> Dissimilar targets and distractors lead to small candidate list and efficient search
> cf. auditory theories – parallel processing followed by limited capacity channel

Question 16

Does visual search look at divided attention? How do we know this?

Answer 16

> Visual search looks at costs of divided (distributed) attention: performance decline with increasing display size is evidence of capacity limitations
Some situations where there is a benefit not to divide attention: avoid processing distractor stimuli

Question 17

Are there instances where you cannot avoid procession irrelevant stimuli?

Answer 17

> Yes, there are limitations of focused attention and involuntary (reflexive) processing of irrelevant stimuli

Question 18

What are some examples of failures of focused attention?

Answer 18

The Stroop Effect (Stroop, 1935)
> Name the COLOUR of the ink in which the word is written; measure RT
> Fast with compatible (e.g. red in red ink), intermediate with neutral (“XXX” in blue ink), slow with incompatible (“blue” in yellow ink)
> enormous compatibility costs - slower in incompatible words

Question 19

What is the explanation of STROOP effect?

Answer 19

> Parallel processing of colour naming and word reading - two memory representation are simultaneously activated
Word reading is fast and involuntary; word name (fast, automatic) available before colour name (slow, controlled), creates output interference
Asymmetrical: no interference of ink colour on word naming (reading word)
Pressing a coloured button match with ink - the effect flips over - no interference of word

Question 20

What is automaticity? What makes a process automatic?

Answer 20

> Word reading: “fast and automatic”
Colour naming: “slow and controlled”
What makes a process automatic? Learned Stimulus-Response associations
Criteria for automaticity: Fast, parallel, effortless, doesn’t require capacity
Automaticity basis for skill acquisition (reading, driving, playing a musical instrument, etc.) - chain together a complex sequence of behaviour
with practice

Question 21

What was the study design of > Shiffrin & Schneider (1977) for studying automatic processing vs controlled processing?

Answer 21

> Search for digit targets in arrays of distractor letters in rapid sequences (or vice versa)
Vary size of target (memory) set: 1-4 items e.g. 4, 7, 3 & 5
Vary size of stimulus displays: 1-4 items (was any target present)
Consistent mapping (CM): target and distractor sets were distinct (something that was used a target on one trial was never used a distractor on another trial)
Varied mapping (VM): targets on some trials were distractors on others

Question 22

What were the results of > Shiffrin & Schneider (1977)?

Answer 22

> Performance under CM became automatic with practice (>90%) (1200 trails = 2 sessions = 2 hrs)
Became independent of memory set and display size - performed in parallel (simultaneously compare all memory set items and all items in display)
Subjectively effortless, spontaneous pop-out of targets from text (e.g. newspaper) = attention capture effect
Never became automatic under VM - even after 20-30 hrs of practice
Requires consistency of target set membership
Consistent with capacity-free, effortless encoding account

Question 23

What is The Eriksen Flanker Task?

Answer 23

EEEEEEE (compatible)
XXXEXXX (neutral)
FFFEFFF (incompatible with the other target alternative i.e. F)
> Task = Is the central character an E or an F? – measure RT
> get the same benefit from compatibility and cost from incompatibility as in the Stroop effect = RT(compatible) < RT(neutral) < RT(incompatible)
> Involuntary processing of flankers even when attempting to ignore them
> Implies some parallel processing of conjunction stimuli
> Failure of focused attention
> The magnitude of compatibility effect decreases with spatial separation between flankers, disappears at 1-1.5 degrees (about the size of favela vision - can be ignored as out of spotlight)
> Provides estimate of size of focus of attention (“spotlight”)
> Stimuli falling within spotlight processed automatically

Question 24

Attention in time - What is the attentional blink?

Answer 24

> Rapid serial visual presentation (RSVP) task
100 ms exposure per item (near temporal resolution of the visual system); each item MASKED by following item (limits amount of info extracted)
Asked to report two targets: report the white letter (T1), detect whether there was an “X” present (y/n) (T2)
Plot second target (T2) performance as a function of the time (lag) since the first target (T1)
T2 performance declines and then recovers – “attentional blink” (at a lag of 3-4 items) and recovers about (8 items)
Only find it when required to report T1 (if T1 ignored, then no blink)
Worst performance not immediately after T1 but some time later (Lag 1 sparing)
Effect takes time to build up, but relatively long lasting (up to 600 ms)

Question 25

What evidence suggests that identification of targets imposes additional processing overheads above and beyond those of monitoring for targets?

Answer 25

> We’re quite good at monitoring multiple display locations or rapid information streams for targets. Some costs for dividing attention.
Identification of targets imposes additional processing overheads above and beyond those of monitoring for targets
—-> Moray (1970) dual target detection deficit (auditory beeps for two simultaneous beeps)
—–> Wolfe (1998) guided search – search guided by parallel processing of display
—–> Attentional blink – found only when first target is processed

Question 26

What is Welford (1952, 1967) Single-Channel Theory?

Answer 26

> Only able to make a decision about one stimulus at a time (identify it, associate with a response)
Decision-making requires time, imposes a central bottleneck on performance
Don’t process all stimuli equally – able to reject nontargets rapidly, in parallel, without extended processing
To identify target, must grab it from stimulus stream, form stable representation in visual (or auditory) short-term memory
Makes us temporarily insensitive to other targets
Need to consider decision-making as well