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