Week 6 Flashcards
Why do we need attention?
• Limitations on what can be processed at
any one time
• We do suffer the effects of attentional
limitations
• Even hands-free mobile phone use by drivers is
associated with an increase in car accidents
• Even if we have enough limbs to perform
actions for two concurrent tasks
• We can usually make only one decision about
action at a time
• We cannot decide on what response to make
for one task without causing a delay in this
response selection for the other task
Capturing attention
• Certain events may attract or “capture” our attention
• Sudden lightning strike, dog running on road, attacker dropping from tree in
movie.
• What makes a stimulus capture attention?
• sudden onset, intense, unexpected in the situation
• what we are looking for (target) and what we are trying to do
• Evidence that stimuli sharing features with targets are more likely to
capture attention
• e.g., red objects if we are looking for a red unmbrella
• Debate about the relative importance of stimulus features
(bottom-up) and expectations (top-down).
Selective attention
Investigating attention in the lab often involves asking
participants (Ps) to respond to a relevant stimulus and ignore
a currently present irrelevant stimulus
• “selective” attention
• usually made difficult by making the irrelevant stimulus on the
current trial serve as the relevant stimulus on other trials
• so participants must select a stimulus from two strongly
competing alternatives
• e.g., Stroop test - name the letter colour and ignore the colour word
RED YELLOW GREEN
Divided attention
• Participants must divide their attention over two or more
concurrent tasks
• as in cooking the dinner while watching TV or doing homework
• Researchers manipulate
• the priority of tasks; e.g., one task is “primary”
• the temporal overlap (overlap in time) of various
components of the tasks
• Ps show attentional limitations that we hope will
inform us about human cognitive processes
So what IS attention?
• a determination of the soul to know something in
preference to other things (Leibniz, 17th
century)
• “Everyone knows what attention is. It is
taking possession by the mind, in clear and
vivid form, of one out of what seem several
simultaneously possible objects or trains of
thought… It implies withdrawal from some
things in order to deal effectively with others.
(William James, 1890)
• The concentration and focusing of mental effort (Best,
contemporary text)
• In the language of cognitive psychology:
• Selecting what is relevant from sensory input and
processing it for appropriate action
• Attention refers to the prioritising of cognitive
operations
Directing attention: Sustaining vs. shifting
We need to maintain or sustain attention in many tasks • e.g., listening to a lecture, following the plot of a film, doing mental arithmetic • But we must be flexible enough to shift attention when required • looking after several children playing on equipment at the park • Neuropsychological evidence for different neural systems for distinct attentional functions - maintaining, disengaging, and directing visual attention - PSYC2020
Shifts of attention:
More about attentional capture
• Shifting attention can be voluntary and directed by
current goals
• endogenous control
• Tuning out of a dull conversation at a party and
tuning into another
• Can be an automatic response to an important stimulus
• exogenous control
• When your attention is captured by hearing your
best friend’s name in a conversation
Inattentional blindness
• When people focus their attention, they often
miss other elements of a scene in plain sight
Change blindness
• Changes in a scene are missed because they occur
alongside a brief visual disruption (Image Flicker,
Eye Movements (saccades), Eye Blink, Occlusions
by Passing Objects, Real world Int-erruptions
So what do change & inattentional blindness
tell us?
Attention is more than where the eyes are
directed
• We perceive only a small fraction of the
external world
• “What we see is what is what we
(attentionally) set”
Objects and locations
• Neurophysiological evidence suggests (somewhat)
separate systems for processing “what” vs. “where” and
“when”
• Attention can operate at the level of objects, not just
regions of space
• In the basketball game, locations in a scene are
searched for objects
• Some objects (gorillas) in the field of view are not
attended
• Stimuli on same object, that is attended, receive
preferential processing
Bálint’s
syndrome:
Simultanagnosia
bilateral occipital/parietal lobe damage prevents patients from perceiving more than 1 stimulus at a time. Grouping stimuli helps this.
Metaphors for attentional limitations
• Structure – bottlenecks, gates, stores (often
shown using boxes & arrows)
• Process – capacity, resources, types of task
demand, spotlight
• The strategic view (Neumann, Allport):
• Limitations are the byproducts of the need to co-ordinate
action and ensure that the correct stimulus information is
controlling the intended responses
• Neumann: (avoid) the behavioural chaos that would result
from an attempt to simultaneously perform all possible
actions for which sufficient causes exist
Historical overview of research
• Helmholtz (1867/1925) performed the first covert attention experiment. • The screen full of letters was larger than his field of view, so he had to select an area to attend to. • Even without moving his eyes, he could still attend to particular locations. Covert vs Overt attention • Unattended locations were just a blur.
Early attention research
• How much info accesses memory for identification & access of meaning? • Attention & memory encoding: How much can you tell us about information that is not attended? • e.g., the people sitting near you when you are watching an engrossing film? • The cocktail party effect • How do we keep track of one conversation; tune out others • But respond when we hear our name in another conversation?
Dichotic listening
• Cherry (1950s): Dichotic listening & shadowing • Ps hear a different message in each ear concurrently, through headphones • Asked to attend to one message (e.g., right ear) and shadow it (repeat it aloud as they hear it). • What can be reported about the unattended message? • Physical features: • Speech vs. music • Gender, pitch, tone of voice • What about meaning? • Meaning is considered to be the end (goal) of the processing path • e.g., visual words: lines …. letters … spelling/ pronunciation ...meaning • How far does processing go for an unattended stimulus?
Meaning of the unattended message
• Early evidence
• Can’t detect that an unattended message with Englishsounding vowels & consonants is in Czech (Cherry,
1953)
• Can’t report meaning of unattended message
• BUT, sometimes Ps hear their own names in the
unattended message (Moray, 1959)
• Broadbent’s filter theory – perceptual features (voice, etc)
used to filter out irrelevant message
• Early selection
• Structural model - filter stops information flow through
the system
• Later evidence
• Sometimes the meaning of the unattended
message has an effect
• Mackay 1973: Used the unattended message to
bias the meaning of a homonym…
River bank, money bank
• Attended message had homograph
• “They threw stones at the bank”
Unattended message had river or money
• Later Ps had to choose sentences closest in
meaning to those in the attended message
• Ps were more likely to choose river meaning if
river had occurred in unattended message
Ps must have processed the meaning of river, even though they couldn’t say
they had heard it.
Bank was dominant
River was subordinate
Late selection: An impasse in the debate
Deutsch & Deutsch and others developed the idea of late selection
• The unattended material is processed all the way to meaning access before
being discarded.
• A test of early vs. late theories: Treisman & Geffen, 1967
• Ps must tap when designated target words appear in either shadowed or
unattended message.
• Target detection = 87% (attended ear) vs. 8% (unattended ear)
• Inconsistent with late selection?
• BUT on late selection: 2 responses (tap & shadow) cannot be organised to
two inputs at the same time
• Difficult to devise a critical test of the theories!
• Inconsistent evidence suggested that the idea of a single structural limitation
was not viable. Nillie Lavie’s Load Theory
Perceptual Load
Perceptual load refers to the complexity of the physical stimuli, particularly the distractor stimuli e.g. a square surrounded by circles is a scene with low perceptual load whereas a square surrounded by lots of different shapes has high perceptual load.
Working Memory Load
The amount of cognitive processing used
Processing capacity
• Kahneman, 1973
• Limitations on processing rather than structure
• Attention is the process of allocating resources to inputs
• Number of concurrent tasks that can be performed depends on
difficulty
= resource demands
• The pool of available resources is increased under arousal (motivation)
• If two tasks can’t be done concurrently, then one must be delayed
Assessing capacity theory
• How to independently assess task difficulty?
• Measure relative task demands under different task combinations
• Suppose Task A + Task C gives 10% impairment of task C (vs. C
alone)
• Whereas Task B + Task C gives 20% impairment of task C (vs. C
alone)
• Then task A is easier than B, yes?
• So task D should suffer less interference with task A than with
task B.
• But this didn’t work out: Could NOT get consistent estimates of task
difficulty!
Contributions of capacity theory
• Useful idea of attentional limitations
• Led to ideas about automaticity – how task demands decrease
with practice
• Spelke, Hirst & Neisser, 1976
• Students Dianne & John trained for 6 weeks, 5 h per week, to
read stories for comprehension while taking words to
dictation
• After training, they could read as fast (and comprehend as
well) with dictation as they could without dictation.
• Extensive practice reduces capacity demands
• restructuring tasks, memorising solutions or establishing rules
for task
The 1980s - new tasks and approaches
• Visual Cognition Revolution
• Response latency the primary dependent variable (DV)
for simple tasks
• Time in milliseconds (ms) from onset of stimulus until
response
• often called reaction time (RT)
• RT increases as stimulus identification, decision making or
response selection becomes more difficult
• Accuracy a better DV for difficult data-limited tasks (e.g.,
masking)
Feature search (Pop-Out)
• Feature (disjunctive) search:
• Search for a red X among black Xs
• PARALLEL
The target shows “pop-out” - an item by item search is not required
Conjunction search
• Search for red X in a background of black Xs and
Red Os
• Vary the number of background items (set size)
• Target present on 50% trials
• Search time as a function of set size
• SERIAL
Effect on RT of increases in the number of search
items, Treisman & Gelade (1980)
Feature (disjunctive) search is fast and
unaffected by search set size
Conjunction search is slower and
affected by search set size
Slope is typically doubled in serial (one-by-one) search when the target is absent.
On average, a target will be found after half of the items have been examined.
If the target is absent, all items are searched (exhaustive search).
Feature integration theory (FIT)
• “Automatic” processing of stimulus into elementary features • Individual feature “maps” give the location of specific features • Individual maps project onto a single location map • Activity in individual map can be read without focused attention • Attention required to bind features into an object
Two kinds of visual search
PREATTENTIVE - Features - Parallel (‘efficient’) - Pop-out - Flat slope ATTENTIVE - Conjunctions - Serial (‘inefficient’) - No pop-out - Steep slope
Limitations of FIT
• Features don’t always “pop out” - you need to search for what is different in
change blindness scenes - e.g., at the restaurant table
• Sometimes configural patterns can over-ride basic features
• Duncan & Humphreys (1989) showed that two factors neglected in FIT had
large effects on RTs:
• Similarity of target to distractors
• Heterogeneity of distractors: Search is much easier if distractors are similar to
each other
Guided Search (Jeremy Wolfe)
Information from top-down and bottom-up processing of the stimuli is used to rank them
in order of their priority (activation maps)
Limitations in visual attention under time pressure :
RSVP
• RSVP = rapid serial visual presentation
• Only one location, but time-pressured
• Letters, digits, words, etc visually displayed, in a single
location, one after the other at a rapid rate.
• Typically about 100 ms per item
• Ps may be asked to look out for certain targets; asked at
the end of list about items (around 15 items).
• Conceptual processing even at this fast rate of
presentation
• Post-target intrusions common
Q X Y Ps report that the X was blue
Two-target RSVP - The attentional blink (AB)
• If Ps must detect 2 targets in the RSVP stream,
there is a decrement in reporting T2 when it
occurs a few hundred ms after T1
• Blink extends out to about T1 + 6
• Blink is not typically observed for the T1 + 1 item
(Lag-1-sparing)
• T1 & T2 processed as one event when T2 occurs
immediately after T1?
The Attentional Blink
• AB is found if T1 and T2 defined in the same way ( 2 digits) or
differently (red letter vs. digit)
• Making T1 easier to identify/report reduces the AB
• AB reflects demands of selecting & identifying T1
• But: AB occurs if Ps have to merely detect T1 without
reporting its identity
• AB not just a recall problem: Interference is observed when a recognition test of targets is used.
• AB is strongly influenced by whether or not items precede and follow
T1 and T2
• or T2 is extremely brief
• Adjacent items serve as pattern masks that curtail processing of the
targets
• Pattern masks compete with targets to engage perceptual processing
• They are commonly used to ensure that brief stimuli do not reach awareness
• Ps say they didn’t see the masked word, but it may be processed sufficiently
to affect responses in tasks
The AB - putting it all together
• Multiple sources of the AB? No account explains all results (Dux &
Marois, 2009)
• Evidence for “resource depletion” – capacity/structural limitations on the
number of targets identified
• Effects of T1 difficulty (more difficult à bigger AB)
• Attentional control mechanisms for selecting targets and rejecting
distractors have a role
• Discriminability of targets and distractors important
• Debate continues about role of distractors in the AB
Attentional limitations under time pressure
• Effects under time pressure = stress testing the system to find
its limits (what aspects of the task are challenging under time pressure?)
• The AB evidence suggests that consolidation of targets in WM is an
operation that can’t be done for more than one target (or targetchunk) at a time
• And it may be associated with competitive or inhibitory effects for other stimuli
