Week 7 : Visual Attention Flashcards
1
Q
alertness
A
refers to a state of vigilance, we are aware, mindful and scanning surroundings… not attending to any particular stimulus but waiting to find out what we should be paying attention to
2
Q
Attention
A
The allocation of our limited cognitive resources to one of many potential stimuli, implies selection
3
Q
Awareness
A
Active thought about something, either physically present or in our imagination
4
Q
Attention is…
A
A set of processes that allow us to select or focus on some stimuli
* - 4 features…
1. 1. Attention can be directed to any of our senses
1. 1. 2. Attention can be directed externally to perceptual features of the world but also internally to our thought process or imaginal process
1. 3. Attention can be sustained or temporary
1. 4. Attention can be overt or covert
5
Q
Selective attention…
A
the processes of attention that allow us to focus on one source when many are present
6
Q
How selective is selective attention… stroop task
A
- participants presented with word list & asked to respond w colour of the word
- conflicting cues are being presented by the text and the colour of the text and it is very difficult to direct our attention to the latter of these stimulus properties
- example of automaticity
7
Q
divided attention…
A
the process of attending to multiple sources of information
8
Q
Automaticity…
A
- sometimes we cannot seem to prevent stimuli from intruding on our cognitive processes
- Automaticity… refers to those cognitive processes that do not require attention, they happen automatically
- both innate and learned
- if u wanna make a learned task automatic, you have to practice a ton
9
Q
Direction of gaze + fovea
A
- usually, we attend to a particular location in space by directing our gaze to that location
- usually, what is represented in our fovea is what we are attending to
- it is only in and near the fovea that we have enough detail to support many of the demands of attention
- BUT.. assumption in sports is that we are capable of directing our attention to places other than our direction of gaze
10
Q
Overt attention…
A
is where our attention lines up with where we are looking (gaze)
11
Q
Covert attention…
A
Is when your visual attention does not line up with your direction of gaze… (often used to obscure one’s intentions such as the basketball played covertly scanning for passing options)
12
Q
Posner paradigm…
A
- the effects of covert attention on visual perception are shown by the Posner paradigm
- In this experiment… participants are asked to focus on a fixation point at the centre of the screen & told that a stimulus will appear in one of 2 positions on the screen (either right or left)
- the participants task is to indicate on which side of the screen the probe appeared
- in some trials, an arrow would appear very briefly and would serve to direct the participants attention toward one side or the other (this shift was in covert attention)
- the arrow is extinguished and the target could appear either on the same side (valid predictor) or on the opposite side (invalid) of the arrow
- sometimes had stimulus onset asynchrony… difference in time between occurrence of one stimulus and the occurrence of the other (e.g. 200ms)
13
Q
Results of Posner paradigm…
A
- in the neutral position condition where covert attention was not directed away from the centre of the screen it took an average 260ms to respond to the target
- when attention was directed away (invalid) from the target stimulus, reaction times were longer
- when the arrow was predictive of the target’s location (valid) reaction times were faster
- this suggests that the direction of covert attention towards the target
14
Q
what does Posner paradigm tell us about attention?
A
- tells us that we can devote attention covertly
- there is a spatial limit to attention, visual attention has a size and in the spotlight we can process what we see there in a more efficient matter than if spotlight not directed there
- the spotlight could be directed away from the region a person is actually looking at
15
Q
Attention functions as a spotlight
A
- the work of Posner and others led psychologists to model visual attention as a spotlight
- suggesting that attention can be directed toward a specific place within visual field… this can help you better resolve details within that region… and draws resources away from the regions to which attention is not being directed
16
Q
Bottom-up drivers of selective attention
A
What directs this attentional spotlight towards a particular region in space?… come from top-down and bottom-up sources
* within our visual field there are particular features that are unique, high in contrast, colourful etc. which direct visual attention there
17
Q
Top-down drivers of selective attention…
A
- if you understand the context of a visual scene you can make more informed choices about where to direct visual attention.. (if u know how actors are gonna move across stage, u know where to put spotlight)
- e.g. watching a baseball game
18
Q
Egly et al. spotlight cueing
A
- participant fixated at centre of screen and visual targets could appear at one of 4 locations; ABCD
- when a cue appeared at the same location but the target subsequently appeared at locations B/C
- both were longer reaction than at position A
- Reactions to B faster than C
- this suggests that the perception of visual objects influence the effects of covert attention
- if attention was cued to the object at right, reaction times were faster for all locations within the object
19
Q
focused attention
A
- gorilla experiment
- demonstrates power of focused attention + the unintended side effects of focusing on the spotlight
- inattentional blindness
20
Q
Inattentional blindness…
A
- the phenomenon in which an object remains outside of conscious perception because visual attention is focused elsewhere
21
Q
Inattentional blindness lab setting…
A
- participants asked to maintain fixation at cross in centre of screen & make response regarding a stimulus presented in the surrounding visual field
- on some trials the fixation point was changed to a diamond but participants were unaware of this change cuz their attention had been directed to the stimuli in the periphery
- changes to an object under direct observation were imperceivable when attention was directed elsewhere
- remember radiologists one with the gorilla in the CT scans
22
Q
Stimulus salience
A
- Stimulus salience refers to the features of objects in the environment that attract our attention (e.g. hearing ur name)
- novel or unexpected capture our attention
- also a stimulus associated with reward ought to attract our attention
- Semantic meaning may also capture our attention in a visual scene, if that meaning is presented in the fovea
23
Q
novelty and violation of expectation
A
- novelty and violation of expectation capture our attention for visual processing
- spent more time looking at the printer on the stove (violation of expectation) than a pot on the stove
- We are adept at ignoring features of the environment that are not changing over time (imagine everything captures your attention)
24
Q
visual search… Feature search…
A
- we can consciously direct our visual attention towards a unique feature or set of features (looking for person in crowd)
- scanning visual field for object with special feature
- conjunction search… 2+ features… task becomes more difficult as number of distractors increase
- spatial configuration search… shape of the target stimulus is the defining feature among a field of similarly shaped distractors… even harder
25
Feature integration theory
- This theory stipulates that some features can be processed in parallel and quickly prior to using attention resources
- Other visual characteristics require us to use attention and are done serially and therefore less quickly
- There are some characteristics that simply pop out at us, but only those that do not require attention
- Conjunctions and configurations searches require attention
26
Change blindness
- Visual search can be extremely difficult
- it's possible that in the presence of numerous distracting stimuli you may miss otherwise obvious changes in visual composition
- referred to as change blindness
- even under overt attention of visual systems may not perceive differences in the visual landscape over time
- e.g. in movies
27
Rapid serial visual presentations...
- same dynamics of change blindness are at play when attention is applied to a confined region of space over time
- lab task to examine temporal dynamics of attention
- often use task in which stimuli presented quickly in succession and participants asked to respond asap to a stimulus w/ a target feature or a conjunction of target features
- if target stimuli are presented too close together in time, participant's response to the 2nd target becomes less reliable (called attentional blink, 500ms)
- it is like the mechanisms that ready and deploy visual attention, require some time to reboot
- or repetition blindness... 200ms
28
2 networks of brain areas that perform processes for visual attention...
1. Orienting attention network
2. Executive attention network
29
orienting attention network
- comprises several areas of the parietal lobe and has been implicated in the type of visual search processes thus far
- allows us to engage in visual search and direct our attention to different locations in visual space
- damage causes unilateral neglect
- work in concert with the executive attention network
30
Executive attention network
- prefrontal lobe
- functions to select stimuli to be attended to and inhibit further processing of those stimuli to be ignored
- inhibit auditory stimuli so we can concentrate on visual stimuli and vice versa
- also serves as an interface between visual perception and cognitive processes like memory
31
Hemifield dominance...
- attention modulates visual activity and these effects are robust for stimuli in the contralateral visual field
- left hemisphere, showing greater activity when attention was directed toward the right visual field
32
Hemifield neglect...
- damage to renting attention network
- specificity of the effects of attention on stimuli in the contralateral field is most apparent in the case of hemifield neglect
- most robust evidence comes from individuals with damage to the orienting attention network
- These patients develop an inability to direct their attention towards stimuli that appear in one half of their visual field (usually left visual world so happen on right)
- patients maintain some knowledge of an objects composition such that when asked to draw the numbers onto an unmarked clock, they recall that it should have 12 numbers, but they use the available space in a way that suggests their incapable of perceiving the left-hand extremity of the image
- most extreme cases patients may even ignore food located on one side of their plate or shave only half of their face
33
Balint's syndrome and stimultagnosia
- Balint's syndrome is a rare condition which function in both the left and right posterior parietal lobes has been compromised
- Patients w this condition have a limited ability to localize objects in space
- This results in difficulty grasping for objects and they seldom move their eyes
- As a consequence of this deficit, they have a condition called stimultagnosia
- Stimultagnosia is a deficit in perceiving more than one object at a time
- Thus, they focus on the one object that is presented directly in front of them and ignore other stimuli
- This is similar to patients w unilateral neglect except they ignore both the left and right visual world
34
Perceptual bistability...
- how you focus your attention on an object can actually influence what you perceive
- perceptual bistability case in which a single image can result in multiple percepts that are often evoked in an alternating fashion
- Classic example is the rabbit-duck illusion
- dynamic bistable stimuli also exist that can appear to have multiple directions of motion or multiple different figures comprised in them
35
Imaging bistability...
- special case of perceptual bistability involves binocular rivalry
- the case in which different images are presented to each eye and the result is a percept that switches back and forth between the 2 images
- classic 3D glasses, but instead of producing 2 images that recreate stereoscopic depth cues, the images presented are of completely different objects
- visual cortex is unable to bind the 2 representations from the eyes in any meaningful and coherent way and the result is a perceptual switch between them
36
Blindsight...
- attention is captured and informs action in the absence of perception entirely
- Blindsight is the phenomenon whereby a person typically due to focal brain damage is rendered unable to perceive objects within part of or within the entirety of their visual field…
- But are able to make accurate judgements about those objects
- neuropsychological phenomenon incredibly informative in creating a picture of how networks that support visual attention, interact with visual processing
- whole field blindsight... more extensive damage to both visual cortices that renders the patient completely blind
37
How is this possible?... we have 2 visual pathways!
- 10% goes to superior colliculus, which in turn presents to there where (dorsal) pathway in order to move the eyes and plan interactions with the environment
- This pathway bypasses the visual cortex, where object perception occurs and projects directly to those regions of the parietal lobe that we saw involved in high-level perception and in the orienting attention network
- Thus, the existence of a second visual pathway may provide sufficient information to make behavioural judgements about stimuli and to plan actions accordingly even in the absence of conscious perception
