Topic 6: Visual Attention Flashcards
Attention
the process of focusing on some objects while ignoring others
attention can enhance the processing of the attended object
Overt Attention
attention that involves looking directly at the attended object
Covert Attention
attention without looking
seeing something “out of the corner of your eye” is an example of covert attention
Dichotic Learning
attention experiment technique involving hearing where dichotic refers to presenting different stimuli to the left and right ears
Selective Attention
occurs when a person selectively focuses attention on a specific location or stimulus property
Shadowing
listener’s repetition aloud of what they hear as they are hearing it
Cocktail Party Effect
the ability to focus on one stimulus while filtering out other stimulus, so called because at noisy parties people are able to focus on what one person is saying even though there are many conversations happening at the same time
Spatial Attention
attention to a specific location
Precueing
a procedure in which a cue stimulus is presented to direct an observer’s attention to a specific location where a test stimulus is likely to be presented
this procedure was used by Posner to show that attention enhances the processing of a stimulus presented at the cued location
Illusory Conjunction
illusory combination of features that are perceived when stimuli containing a number of features are presented briefly and under conditions in which focused attention is difficult
for example, presenting a red square and a blue triangle could potentially create the perception of a red triangle
Feature Integration Theory (FIT)
a theory proposed by Anne Treisman to explain how an object is broken down into features and how these features are recombined to result in a perception of the object
Pre-attentive Stage
an automatic and rapid stage of processing, proposed by Treisman’s feature integration theory, during which a stimulus is decomposed into individual features
Focused Attention Stage
the stage of processing in feature integration theory in which the features are combined
according to Treisman, this stage requires focused attention
Binding
the process by which features such as colour, form, motion, and location are combined to create our perception of a coherent object
binding can also occur across senses, as when sound and vision are associated with the same object
Visual Search
a procedure in which a person’s task is to find a particular element in a display that contains a number of elements
Feature Search
a visual search task in which a person can find a target by searching for only one feature
an example would be looking for a horizontal green line among vertical green lines
Conjunction Search
a visual search task in which it is necessary to search for a combination (or conjunction) of two or more features on the same stimulus to find the target
an example of a conjunction search would be looking for a horizontal green line among vertical green lines and horizontal red lines
Fixation
the brief pause of the eye that occurs between eye movements as a person scans a scene
Saccadic Eye Movement
rapid eye movement between fixations that occurs when scanning a scene
Corollary Discharge Theory
the theory that explains motion perception as being determined both by movement of the image on the retina and by signals that indicate movement of the eyes
Motor Signal (MS)
in corollary discharge theory, the signal that is sent to the eye muscles when the observer moves or tries to move his or her eyes
Corollary Discharge Signal (CDS)
a copy of the motor signal that is sent to the eye muscles to cause movement of the eye
the copy is sent to the hypothetical comporator of corollary discharge theory
Image Displacement Signal (IDS)
in corollary discharge theory, the signal that occurs when an image moves across the visual receptors
Comparator
a structure hypothesized by the corollary discharge theory of movement perception
the corollary discharge signal meet at the comparator to determine whether movement will be perceived
Predictive Remapping of Attention
process in which attention begins shifting toward a target just before the eye begins moving toward it, enabling the perceiver to experience a stable, coherent scene
Visual Salience
characteristics such as bright colours, high contrast, and highly visible orientations that cause stimuli to stand out and therefore attract attention
Attentional Capture
occurs when stimulus salience causes an involuntary shift of attention
for example, attention can be captured by movement
Saliency Map
a “map” of a visual display that takes into account characteristics of the display such as colour, contrast, and orientation that are associated with capturing attention
Same-Object Advantage
the faster responding that occurs when enhancement spreads within an object
faster reaction times occur when a target is located within the object that is receiving the subject’s attention, even if the subject is looking at another place within the object
Perceived Contrast
the perceived difference in the appearance of light and dark bars
Inattentional Blindness
a situation in which a stimulus that is not attended is not perceived, even though the person is looking directly at it
Change Blindness
difficulty in detecting differences between two visual stimuli that are presented one after another, often with a short blank stimulus interposed between them
also occurs when part of a stimulus is changed very slowly
Continuity Errors
mismatch, usually involving spatial position or objects, that occurs from one film shot to another
Operant Conditioning
a type of learning in which behavior is controlled by rewards, called reinforcements, that follow behaviors
Spatial Neglect
neurological condition in which patients with damage to one hemisphere of the brain to not attend to the opposite side of their visual world
Extinction
a condition associated with brain damage in which there is a lack of awareness of what is happening in one side of the visual field
Pre-attentive Processing
hidden processing that happens within a fraction of a second, below one’s level of awareness
Meditation
a practice that originated in Buddhist and Hindu cultures, which involves different ways of engaging the mind
Focused Attention Meditation
common form of meditation in which a person focuses on a specific object, which can be the breath, a sound, a mantra, or a visual stimulus
Mind Wandering
non-task-oriented mental activity
also called daydreaming
Experience Sampling
technique used to measure the thoughts, feelings, and behaviors of people at various random points in time during the day
the technique has been used to measure the frequency of mind-wandering
Head-Mounted Eye Tracking
eye tracking technique in which the perceiver is fitted with two devices: a head-mounted scene camera, which indicates the orientation of the perceiver’s head and their general field of view, and an eye camera, which indicates the precise location where the person is looking within that field of view
What is attention?
mental processes for seeking out and focusing on relevant (visual) stimuli, which are consequently processed to a greater extent (at the expense of other stimuli)
Why is the amount of information processed in vision limited?
sensory systems are limited (e.g. visual fixations, size of foveal gaze)
motor systems are limited (e.g. movements planned/words spoken sequentially)
What are saccades?
small, rapid eye movements
What is saccadic suppression?
attenuation in some spatial frequencies during saccade
neither motion of the eye/motion blur nor gap in perception is detected
begins before eye movement (thus, is not an optical effect)
What are fixations?
pauses that typically indicate where a person is attending
about 3 fixations/second
What determines fixation locations?
visual salience: color, contrast, orientation (bottom-up process)
picture meaning/observer knowledge: what do you expect to see? (top-down processing)
task demands: what are you being asked to do?
What is overt attention?
directing foveal gaze (and attention) to a stimulus
What is covert attention?
directing attention to a stimulus in peripheral vision
What was the Helmholtz (1896) study on covert attention?
put matrix of letters on wall, with fixation cross in the centre
fixated on cross and turned light off
directed his attention (not his eyes) to a certain location, then briefly illuminated room with a spark
could perceive letters in attended region, but not in other regions
attention can be used to select stimuli independent of fixation
What is a selective attention task?
requires responding to a stimulus while ignoring others
e.g. reading a textbook while trying to ignore interruptions
What is a divided attention task?
requires attending to two or more simultaneous stimuli
e.g. driving, drinking a coffee, and talking on cell phone at the same
What did Michael Posner, Nissen, & Ogden (1978) believe where the components of attention?
attention viewed as a spotlight: can focus on certain locations
- disengaging attention from current location
- moving attention to new location
- engaging attention in new location
What conclusions did Michael Posner, Nissen, & Ogden (1978) come to after their study?
reaction time affected by type of cue
attention can be directed to a particular location, which enhances perceptual processing
if cue is invalid, attention must be disengaged, moved, and re-engaged
attention is not only exogenous or “stimulus-driven” (bottom-up), but also endogenous or “goal-directed”
What does Balient’s syndrome have to do with attention being object-based?
patients experience more illusory conjunctions; deficit in locating targets in conjunction search
What does simultanagnosia have to do with attention being object-based?
difficulty in attending to more than object at a time – even when overlapping
supports the idea that attention can be object based
syndrome may be due to inability to shift attention among objects
What is unilateral neglect?
deficit in awareness of items on one side of space, due to brain damage
damage results in neglect of objects (or parts of objects) in the contralesional visual field
patients often unaware of this deficit
typically due to damage in right posterior parietal cortex, critical to attention and selection
What are the explanations for unilateral neglect?
problem in disengaging attention from ipsilateral (same) side; cueing (directing attention) helped reduce spatial biases
disruption of balance between hemispheres in directing attention; more stimuli on ipsilateral side hampers attention to contralateral (opposite side) items
however, syndrome may be object-based: left side of object neglected, rather than the left side of space
patient with object neglect cannot detect differences on the left side of an object – even when it falls into the right visual field
What is egocentric neglect?
unaware of one side of space
11 people overlooked complete apples on the left side of the page; 2 people missed complete apples on the right side
brain damage was clustered in right anterior cortical regions, and subcortical structures
What is allocentric neglect?
unaware of one side of objects
8 people crossed out apples with gaps on their left side; 2 people crossed out apples with gaps on their right side
brain damage was in right posterior cortical regions
What are the implications of the existence of both egocentric and allocentric neglect?
these different forms of neglect may reveal the nature of attentional processing
attention may be either location-based or object-based
different parts of the brain process different kinds of attention
damage to location-based system produces egocentric neglect, damage to object-based system produces allocentric neglect
location-based processing is better suited to static scenes, whereas object-based processing works well for following a moving object in dynamic scenes
What is inattentional blindness?
stimulus that is presented, but is not attended, is not perceived
a.k.a. “looked-but-didn’t-see” problem
What is change blindness?
an inability to detect changes in an object or a scene
What are the implications of inattentional and change blindness?
not everything presented to our senses is processed
attention is limited
visual encoding must be selective or “sparse”
What is the binding problem?
how are the independent, parallel subsystems in vision (form, motion, color, etc.) fused together into a unitary percept
how are the parts of an object unified into a whole?
What is the convergence solution to the binding problem?
Hubel & Wiesel (1977)
neurons coding for different aspects of an object (e.g. color, form, etc.) converge on a single neuron detecting that particular combination
implies we have a neuron for every object we can recognize (“grandmother cell” theory)
problems: little evidence, we can recognize too many objects, cannot account for perception of novel objects
What is the temporal synchrony solution to the binding problem?
neurons that signal different aspects of the same object fire in synchrony
synchronization does not occur if each assembly is triggered by a different stimulus
objects symbolized by synchronized population coding
attention may help synchronize neural firing
What is feature integration theory?
developed by Anne Treisman
attention must be focused on particular stimulus attributes or parts in space to construct a representation or percept
What is the preattentive stage of feature integration theory?
rapid, automatic decomposition of stimulus into a number of basic properties (“primitives”)
processing is in parallel
What is the focused attention stage of feature integration theory?
serial process
spatial location selected
primitives existing at this spot are combined (e.g. redness and X-ness combined into red X-ness)
combination object is called object file only exists temporarily to be examined by focused attention
What is a visual search task?
primitives determined via visual search experiments
task: find target among nontargets/”distractors”
observers asked whether a display contain target
RT (and errors) are recorded
What is a feature search task?
target defined by one basic property/primitive
e.g. find a green 2 among red 2s
What is a conjunction search task?
target defined by a combination of two or more basic properties/primitives
e.g. find a green 5 among green and red 2s, and red 5s
What is a spatial configuration search?
target defined by organization of features
e.g. find a 5 among 2s
What is a pop-out?
time needed to find the target is very short/constant
lots of slow, serial processing not required
RT not influenced by the number of distractors
primitives cause pop-out in feature search: e.g. color, brightness, orientation, length, curvature, etc.
What are the pros of visual search tasks?
evidence: illusory conjunctions; when attention is overtaxed, primitives may be incorrectly combined
e.g. red Xs, blue Os: you may perceive a blue X
e.g. Stroop effect (1935): shows attention inhibition of automatic cognitive processes
What are the cons of visual search tasks?
with practice, conjunction search may become automatic/parallel
at attention necessary for perception?
how can we be aware of anything that we are not attending to?
how can we shift our attention to a new stimulus, if we aren’t aware that is exists yet?
cases of brain damage (e.g., blindsight) can reveal perception without awareness
