Attention 2 Flashcards
What is hemispatial neglect?
Also known as unilateral neglect, hemineglect or spatial neglect is a common neuropsychological condition in which patients ignore one side of space
Where is neglect most common, prominent and long lasting?
- After damage to the right hemisphere of the brain (typically right parietal damage), particularly following a stroke
- Patients fail to identify, act upon or acknowledge contralesional (on the opposite side of the lesion) stimuli and only acknowledge stimuli which are ipsilesional (on the same side as the lesion)
Is it possible to knowingly have neglect?
Yes but many people will deny they have a deficit (agnosia)
What are tests for neglect?
- Cancellation task (cancel out everything they can see on the page)
- Line bisection task (asked to draw a line through the middle of 3 lines)
What is/isn’t the border between neglected and non-neglected spaces?
- Not sharp and absolute as in a primary visual field deficit such as hemianopia
- Does not necessarily align with the vertical midline or meridian
- Can vary with the number of distractor items in the display (Kaplan et al,. 1991)
- Not all or none
What was Marshall and Halligan’s (1988) experiment to see if anything is processed in neglect and what were the results?
- Presented patients with two houses. One had smoke coming out of the window (on the left side) where they neglect patients would not be able to see it. They asked which house they wanted to live in
- Expected Ps to evenly choose the two houses as they would not see the smoke
- However most Ps chose the house without smoke but usually couldn’t give a reason showing they still had some semantic viewing of the left side, just not conscious.
- So there is some processing of information presented to the neglected side, but the patient is not consciously aware of the neglected stimuli
What was Bisiach’s and Luzzatti’s Piazza del Duomo experiment (1978) and what were the findings?
- Bought neglect patients into lab and asked if they were familiar with a famous square in Milan. Everyone said yes
- Authors asked everyone to imagine they were standing at the end of the square facing the cathedral and ask them to describe it
- Patients all describe RH side of the square as they perceive in their viewpoint and all left out the left side
- Authors then said ‘imagine you get up and cross the square to the other side and you face the square with your back to the cathedral’
- Patients now reported what was on the new right hand side and neglected what was on the left hand side.
- Shows that neglect is applied to memories as well.
What are the two theories about what is happening in neglect patients?
- Exaggeration of normal functioning – we choose what to attend to (Driver and Vuilleumier, 2001)
- Presence of extinction strongly suggests that there’s some sort of competition
Presence of a more salient stimulus on the ipsilesional side of space captures attention and hinders perception of the stimulus on the contralesional side
Can be alleviated by presenting stimuli (e.g. wine bottle and wine glass), one to each side, as this is more likely to be seen as an integrated whole than as two separate stimuli (e.g. Riddoch et al. 2006)
What is visual search?
- Looking for something in a cluttered visual environment
- Find the target among the non-targets (‘distractors’)
- Very common in everyday life
What is a visual search task and what are the findings
- Target (e.g. green G) presented on half the trials and have to respond if target is present or not:
- If only green items in display the response time doesn’t vary and it is quicker
- If Different colour items in display the response time is slower and it is much harder to solve the task if there are more distractors
- the set size can be varied
If reaction time is varied by display size what sort of processing does that suggest?
Serial processing
If reaction time is not affected by display size what sort of processing does that suggest?
Parallel processing
What is TReisman and Gelade’s (1980) feature integration theory? (FIT)
- Two Stage process. Which two stages you need depends on the target and how that target is defined relative to the distractors
- Object (search display) -> Pre-attentive stage (Ps can tell what features are in the display but not how the features are defined) -> Focused attention stage (features combined, e.g. you see the green G) -> perception
Give features of the pre-attention stage according to FIT
- It is parallel and you don’t need attention
- Processes physical characteristics - features
- Targets that are identified by simple physical characteristics ‘pop-out’
Give features of the focused attention stage according to FIT
- It is serial and you do need attention
- Allows targets to be defined by a conjunction of features
- slower than parallel processing and depends on set-size
What are illusionary conjunctions and when can they occur?
- Random (incorrect) combinations of features
- Occurs in serial processing due to problems in combining features to form objects at a relatively late stage
How was the FIT experiment carried out and what were the results?
Single Feature targets: T among S
Conjunctive targets: T among L and T
Quicker RT with single feature targets
With single feature targets with positive trials the RT is lowest and display size doesn’t make a difference
With negative single feature trials the response time is higher and it increases with increasing display size (the line is still fairly flat though)
With Positive conjunctive target trials the RT is slower than the single features targets and is slower with larger display size
With negative conjunctive target trials the RT is slower and varies the most with display size
This because for positive trials we need to check through half the options to get to the target whereas on negative trials we have to search through all the options
What are the weaknesses of FIT?
- Assumption that visual search either all serial or all parallel is too strong
- Search for conjunctive targets faster than predicted by feature integration theory
- Nature of non-targets in display also important (similarity among distractors speeds search, Duncan and Humphreys, 1989, 1992)
- Not all features are equal
What is the threat superiority effect?
We are faster to notice something potentially threatening compared to something positive or neutral
What are the three factors that affect whether or not we can successfully multitask?
- Task difficulty
- Task Similarity
- Practice
What was Sullivan’s (1976) experiment with task difficulty?
- Dichotic shadowing task while detecting a target word in the non-attended message
- When the shadowing task was made more difficult (less predictable), fewer targets were detected
What did Treisman and Davies (1973) find in regards to task similarity?
two tasks interfered much more when both tasks in same modality (sense e.g. two visual)
What was McLeod’s similarity experiment (1977)
- Motor tracking + auditory target
- Response either motor (other hand button press) or spoken
- Found response was much more difficult to make with their hand because it was too similar to holding a joystick (motor tracking)
What was Segal and Fusella’s (1970) experiment and what were the findings?
- Asked participants to either imagine a song or visual scene if their head
- Would then be played a auditory signal and visual signal and have to detect it.
- Measured volume or brightness for participants needed to detect this stimuli while they were imagining something in their head
- found that low sensitivity means we need more of it in order to detect it
What was Spelke, Hirst and Neisser (1976)’s experiment about practice?
- Tasks – read story while writing down dictated words
- 2 Ps (Diane and John) – 5 hrs training per week for 4 months
- After 6 weeks both improved but recall and semantic processing of dictated words still poor
Later could write down categories to which words belonged
What was the problem with Spelke, Hirst and Neisser’s experiment?
- Focused on accuracy rather than speed (less sensitive measure)
- Reading task could be done flexibly according to the demands of the secondary task
- Suggests they may have got better at task switching rather than doing two things at once
What are the two theories to explain divided attention?
- Central Capacity
- Multiple Resources
What is the Central Capacity Model?
- Assume there is some central capacity (central executive) which can be used flexibly across a range of activities
- Central capacity has limited resources (‘attention’) so how successfully multiple tasks can be performed depends on the drain of each task on these resources
- Any two tasks will interfere provided they require more resource than is available in the total capacity
What is Bourke et a,. (1996) experiment about central capacity?
- Used 4 tasks which required different amounts of the ‘central capacity’:
Random letter generation
Pattern learning
Manual task
Tone detection - Tested ability to do two of these tasks at once with one primary and one secondary
- Findings consistent with central capacity theory
- Task which loaded on the central capacity interfered most
- Quite a circular theory
What is the multiple resources model - Wickens (1984) ?
- Separate sources of capacity may be specialised for particular processes
- Three successive stages of processing
1. Encoding – perceptual processes (detecting visual/auditory)
2. Central processing – spatial or verbal codes (infer meaning)
3. Response – vocal or manual - Selective interference
It’s the type of resources that tasks require that determines whether they will interfere with one another
The same modalities for all processing stages makes it more likely to interfere - Supporting evidence
More interference when tasks share a modality (e.g. both auditory) or a type of response (e.g. both verbal)
What’s the problem with Wickens multiple resources model?
- Models really focus on visual and auditory inputs but tasks could be presented in other modalities
- Coordination between tasks not really considered
What’s the Psychological Refractory Period (PRP)?
- Ps given two stimuli
- Two responses
- Respond to each stimulus as rapidly as possible
- Second stimulus presented shortly after the first one
- A marked slowing to the second stimulus
- example of cognitive bottleneck
What did Pashlet et al. (2001) say about PRP?
- Response to the second stimulus is slowed because Ps are still processing the first stimulus
- Results delayed in response time when asked to divide attention
What did Shriffrin and Schneider (1977) say about automatic processes?
- Fast
- Does not require attention or cognitive resources
- Doesn’t reduce capacity for performing other tasks
- Parallel processing
- Unavailable to consciousness
- Unavoidable (i.e. always occur when appropriate stimulus presented even if outside the field attention
- Very hard to modify once learned
What did Shriffrin and Schneider (1977) say about controlled processes?
- Slow
- Require attention
- Take up processing capacity
- Serial processing
- Available to consciousness
- Can be used flexibly in changing circumstances (can turn on and off depending on task demands)
How did Norman & Shallice (1986) distinguish between different levels of automaticity?
- Fully automatic (controlled by schemas, organised plans)
- Partially automatic (e.g. contention scheduling – making a cup of tea)
- Deliberate control by SAS: new tasks, deliberate planning, problem solving, conflict monitoring
What is the supervisory attentional system (SAS)
- Involvement of the frontal lobes and in specific the medial ones
- Thought to be a specific part of the brain involved in Control of tasks
What is dysexecutive syndrome?
- Cognitive, emotional, behavioural symptoms
- Often associated with frontal lobe damage (e.g. Phineas Gage)
- Patients often have difficulty in planning, organizing and controlling action
What is Utilization behaviour (Lhermitte 1983)
- Associated with medial frontal lesions
- Patients will grasp and utilize any object that is presented even if this behaviour is inappropriate
- Patients likely to come up with a reason that makes sense (confabulate)
- Shows patients have difficulty controlling their reflexive behaviours
- Example of dysexecutive syndromes
What does top-down control/ executive functions/ supervisory attention system do?
Monitor performance Detect conflict and resolve it Flexibly switch between responses Inhibit inappropriate responses Keep track of where the system is and was Sustain attention on current goals Planning
What is the homunculus problem?
what is controlling the controller (in your brain)?
What is subject-centred/ egocentric neglect?
When the brain damage is in the right hemisphere and there is little awareness of stimuli on the left side of the visual field
What is object-centred/allocentric neglect?
a lack of awareness of the left side of objects rather than simply the left side of the visual field
What is extinction?
a failure to detect a stimulus presented to the side opposite the brain damage when a second stimulus is presented to the same side as the brain damage
What did Corbetta and Shulman thought happened in neglect? (2011)
the bottom-up ventral attention network is typically damaged. Assumes the damaged ventral attention system impairs the functioning of the dorsal attention network because the two systems interact. They think that neglect patients have an intact dorsal attention network but reduced attentional resources
What did Duncan and Humphreys discover in regards to visual search?
- Search is faster when distractors are similar to each-other because it is easier to identify them as distractors
- There is similarity between the target and distractors. The number of distractors has a large effect on time to detect
Why should detection times not depend on the number of items in display if the processing is serial?
The first item analysed should always be the target
Why in parallel processing does the target detection time increase the more distractors there are?
Because observers need to take in information from all the targets
What did Ophir think about multitaskers?
thought that low level multitaskers are more likely to have top-down attentional control. Low multitaskers made effective use of top-down instructions to reduce distraction and enhance performance
What is focal vision used for?
Object recognition
What is ambient vision involved in?
Perception of orientation and movement
What is Pashler’s et al. 2008 central bottleneck theory?
prevents more than one central decision (from one of the three task decision stages: perceptual, central and motor) process from operating at any given moment
