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Ch4 : Attention - Coggle Diagram
Ch4 : Attention
Processing Capacity and Perceptual Load
Demonstration : The Stroop Effect
The ability to ignore task-irrelevant stimuli is also a function of how powerful the task-irrelevant stimulus is
E.g., when the task-irrelevant stimulus is very salient
E.g., Stroop effect
Stroop Effect
Participants
asked to report the color of the ink of a word, not the color name that is spelled out
Processing capacity: how much information a
person can handle at any given moment（請參考後面對於cognitive capacity vs.
perceptual capacity的補充）
Perceptual load: related to the difficulty of a given task
High-load (difficult) tasks use higher amounts of processing capacity
Low-load (easy) tasks use lower amounts of processing capacity
Load theory of attention (Lavie): early vs. late selection can be explained in terms of perceptual load
Low perceptual load
Still capacity left
Resources are available to process the
task-irrelevant stimulus
High perceptual load
No resources remain to process other stimuli
Appendix: Processing Capacity and
Perceptual Load
High perceptual load experiments support early selection
E.g., Broadbent's dichotic listening experiments
Low perceptual load experiments support late selection
E.g., only a single word was presented to the unattended ear in McKay's experiments
Perceptual capacity: a person has a certain capacity that can be used for carrying out perceptual tasks
Perceptual load: the amount of perceptual capacity needed to carry out a perceptual task
High perceptual load: more objects to be perceived, or perceptual analysis is difficult => uses almost all perceptual resources
Low perceptual load: less objects to be perceived, or perceptual analysis is easy => uses few perceptual resources
Cognitive resources: a person has a certain cognitive capacity (including cognitive control)
Cognitive load : how much of a person's cognitive resources are used to accomplish a
task
High-load: uses almost all; no resources for other tasks
Low-load: uses few; resources for other tasks
Appendix: Video-Game Experts
Low perceptual load: experts' performance is similar to non-experts
High perceptual load: experts still had enough resources left to process distractors
Performance transferable to flanker-compatibility task
Attention as Information Processing
Broadbent's Filter Model of Attention
Broadbent's filter model of attention (1958)
Flow diagram representing what happens as a person directs attention to one stimulus
Unattended information does not pass through the filter
Cherry (1953)
Dichotic listening
One message is presented to the left ear and another to the right ear
Participant "shadows" one message to ensure he is attending to that message
Can we completely filter out the message to the unattended ear and attend only to the shadowed message?
Participants could not report the content of the message in unattended ear
Knew that there was a message
Knew the gender of the speaker
Cocktail part effect
The ability to focus on one stimulus while filtering out other stimuli
Moray (1959) : unaware of a word that had been repeated 35 times in the unattended ear
Sensory memory
Holds all incoming information for a fraction of a second
Transfers all information to the filter
Filter
Identifies attended message based on physical characteristics
Only attended message is passed on to the next stage
Detector
Processes all information that enters it
Determine higher-level characteristics of the message
Short-term memory
Receives output of detector
Holds information for 10-15 seconds and may transfer it to long-term memory
A bottleneck model : the filter restricts information flow much as the neck of a bottle restricts the flow of liquid
An early-selection model : the filter eliminates the unattended information right at the beginning of the flow of information
Modifying Broadbent's Model : More Early Selection Models
Participant's name gets through
Moray (1959) : When presenting the listener's name to unattended ear, about 1/3 of the participants detected it
Participants can shadow meaningful messages that switch from one ear to another
Dear Aunt Jane (Gray & Weddeburn, 1960)
Treisman's Attenuation Model
Attenuator
Analyzes incoming message in terms of
Physical characteristics
High- or low-pitch, fast or slow
Language
How the message groups into syllables or words
Meaning
How sequences of words create meaningful phrases
Proceeds only as far as is necessary to identify the attended message
Once the attended and unattended messages are identified
Attended message is let through the attenuator at full strength
Unattended message is let through at a much weaker strength
This model is called a "leaky filter" model because at least some of the unattended message gets through the attenuator
The final output of the system is determined by the dictionary unit
Dictionary unit
Contains words, each which have thresholds for being activated
Threshold: The smallest signal strength that can barely be detected
Words that are common or important have low thresholds
Uncommon words have high thresholds
An early selection model
Proposing a filter that operates at an early stage in the flow of information
A Late Selection Model
Selection of stimuli for final processing does not occur until after information has been analyzed for meaning
McKay (1973)
In attending ear, participants heard ambiguous sentences
"They were throwing stones at the bank."
In unattended ear, participants heard either
"river"
"money"
In test, participants had to choose which was closest to the meaning of attended to message
They threw stones toward the side of the river yesterday
They threw stones at the savings and loan association yesterday
The meaning of the biasing word affected participants' choice
Participants were unaware of the presentation of the biasing words
Attention
Attention: the ability to focus on specific
stimuli or locations
Selective attention: attending to one thing while ignoring others
Distraction: one stimulus interfering with the processing of another stimulus
Divided attention: paying attention to more than one thing at a time
Attentional capture: a rapid shifting of attention usually caused by a stimulus such as a loud noise, bright light, or
sudden movement
Visual scanning : movements of the eyes from one location or object to another
Attention has a large effect on what we are aware of
William James (1890)
Millions of items...are present to my senses which never properly enter my experience.
Why? Because they have no interest to me. My experience is what I agree to attend to....Everyone knows what attention is. It is the 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.
Outcoms of Attention
Attention Improves Our Ability to Respond to a Location
Precluding : directing attention without moving the eyes
Participants respond faster to a light at an expected location than at an unexpected location
Even when eyes kept fixed
Attention Improves Our Ability to Respond to Objects
Location-based
attention to locations
moving attention from one place to another
Object-based
attention to objects
attention being directed to one place on an object
Egly et al. (1994)
Participants saw two side-by-side rectangles, followed by a target cue
Reaction time fastest when target appeared where indicated
Reaction time was faster when the target appeared in the same rectangle
same-object advantage
Location-based and object-based attention activate different areas of the brain (Shomstein & Behrmann, 2006)
Attention can be based on the
Environment
static scenes or scenes with few objects
Specific object
dynamic events
Attention Affects Perception
James: attention to objects as "taking possession by the mind in clear and vivid form"
Attended objects are perceived to be
Bigger and faster
More richly colored
Better contrast
Experiment by Carrasco et al.
Observers saw two grating stimuli with either similar or different contrast between the bars.
Task was to fixate on center point between gratings and indicate orientation of bars with higher contrast.
Small dot was flashed very quickly on one side before gratings appeared.
Results showed that
when there was a large difference in contrast, the dot had no effect.
when the contrast was the same, observers were more likely to report that the grating preceded by the dot had higher contrast.
the shift of attention led to an effect on perception
Attention Affects Physiological Responding
Attention to Locations Increases Activity in
Specific Areas of the Brain
Datta and DeYoe (2009)
Attention maps show how directing attention to a specific area of space activates a specific area of the brain.
Topographic map: each point on a visual
stimulus causes
activities at a specific location on the visual cortex
<Appendix> Attention to Objects Increases Activity in Specific Areas of the Brain
O' Craven (1999)
Participants attended to the house or face
Attending to the moving or stationary face caused enhanced activity in the
FFA
Attending to the moving or stationary house caused enhanced activity in the PPA
Attention Changes the Representation of
Objects Across the Cortex
Cukur and coworkers (2013)
How attention affects the way different types of objects are represented across the brain
One group : passively view the movies
The second group : search for humans
The third group : search for vehicles
Attentional warping : the map of categories on the brain changes so more space is allotted to categories that the being searched for
Even when the attended category isn't present
Directing Attention by Scanning a Scene
Over Attention : Scanning a Scene With Eye Movements
Saccades - rapid movements of the eyes from one place to another
Fixations - short pauses on points of interest
Studied by using an eye tracker
Earlier method: Attaching small mirrors and lenses to the eyes
Modern method: Camera-based eye trackers
Scanning based on stimulus salience
Stimulus salience: the physical properties of the stimulus, such as color, contrast, or movement
Bottom-up process
Depends on characteristics of the
stimulus
Saliency map
Analyzing characteristics such as color, orientation, and intensity at each location in the scene and then combining these values
Scanning based on cognitive factors
Scene schema: knowledge about what is contained in typical scenes
Is also associated with top-down processing
Help guide fixations from one area of a scene to another
Another example : how cognitive factors based on knowledge of the environment influences scanning
Shinoda et al. (2001)
Observers' fixations were measured during computer simulated driving
They were more likely to detect stop signs when they were at intersections
People have learned that this is where stop signs are typically placed
Scanning based on task demands
Key findings : eyes movements are determined by task
Eyes movements preceded motor actions by a fraction of a second
Scanning is influenced by predictions
Anticipation: what a person is going to do next, stop signs are most likely to be located at intersections....
When expectation is violated: looking longer at an unexpected objected
Overt attention
Shifting attention from one place to another by moving the eyes
Covert attention
Shifting attention from one place to another while keeping the eyes stationary
Divided Attention: Can We Attend to More Than One Thing at a Time?
Divided attention : The distribution of attention to two or more tasks
Depends on a number of factors, including practice and the difficulty of the task
Dived Attention : Can Be Achieved with Practice : Automatic Processing
Schneider and Shiffrin (1977)
Divide attention between remembering target and monitoring rapidly presented stimuli
Memory set : 1-4 target characters
Test frames : could contain random dot patterns, a target, distractors
If task difficulty is increased, automatic processing is not possible even with practice
by using letters for both targets and distractors
and by changing targets and distractors on each trial so a target on one trial can be a distractor on another
Example: driving
Over time, participants became able to divide their attention
Participants reported that after about 600 trials, the task had become automatic : The frames appeared and participants responded without consciously thinking about it
Automatic processing occurs without intention and only uses some of a person's cognitive resources
Automatization - Two Explanations
Integrated components theory (Anderson)
Practice leads to integration; less and less attention is needed
Instance theory (Logan)
Retrieve from memory specific answers, skipping the procedure; thus less attention is needed
<Appendix> Divided Attention Can Be
Achieved with Practice: Automatic Processing
Practice enables people to simultaneously do two things which at first were difficult
Spelke et al. (1976)
Before practice, participants could not read short stories and take dictation at the same time
After 85 hours of practice spread over 17 weeks, they could read and categorize dictated words