Chapter 4-Attention Pt. 2 Flashcards
Overt Attention
Eye movements, attention, perception
Saccades: rapid movements of the eyes from one place to another
Fixations: short pauses on points of interest (studied by using an eye tracker)
Stimulus Salience
Areas that stand out and capture attention
- bottom up process
- depends on characteristics of the stimulus
- colour and motion are highly salient
Scene Schema
Knowledge about what is contained in typical scenes
- top down process
- help guide fixations from one area of a scene to another
Eye movements are determined by ______
Task
Eye movements preceded motor actions by a fraction of a second
Vo and Henderson
- top down process and eye movement
- kitchen scene
- participants looked longer at the printer than at the pan
- demonstrates how eye movement is guided by people’s previous knowledge
Covert Attention
Attention without eye movements
Precueing
Directing attention without moving the eyes
Participants respond faster to a light at an expected location than at an unexpected location even when the eyes are kept fixed
Attentional cues experiment
Posner
Focus visual attention to an area using a cue
Measure time to identify target when:
- observer does not know where item will appear
- observer does know where item will appear
Results: cue versus no cue
Advance knowledge of location improves performance
Amount of reduction depends on distance from cue (Downing and Pinker 1985)
Exogenous cue
Outside generating
- low level reflexes
- sudden change (e.g. flash or movement)
- draws attention automatically
- bottom up control of attention
- based on what is actually happening in the environment
Endogenous cues
Inside generating
-high level control
-instruction (via some kind of visual sign or pattern)
-sends attention to requested location
-top down control of attention
-based on what the observer believes
E.g. interpreting meaning of the arrow
Inhibition of return (IOR)
Klein (2000)
If the time interval between cue and target are too long you will see opposite results (e.g. valid cue becomes longer than invalid)
People first direct their attention to the direction of the cue. After 200 ms interval passes before target is shown, Attention is shifted to the opposite direction than suggested by the valid cue
In addition to paying attention to the location of objects (via spatial cues), people can also ______
Pay attention to the movement of objects
Object Based Visual Attention
Location based: moving attention from one place to another
Object based: attention being directed to one place on an object
Egly et. al
- 1994
- object based visual attention
- participants saw two side by side rectangles, followed by a target cue
- reaction time fastest when target appeared where indicated (A)
- reaction time faster when target appeared in same rectangle (B) even though B and C had same DISTANCE to cue
Attention can be based on
The environment (static scenes or scenes with a few objects)
Specific object (dynamic events)
The enhancing effect of attention spreads throughout the object
Divided Attention
Practice allows people to simultaneously do two things that were difficult at first
Schneider and Shiffrin (1977)
- memory set (1-4 target characters)
- test frames (contained distractors, flashed rapidly)
Had to remember the memory set and say if it appeared in the test frames
Results of Schneider and Shiffrin’s divided attention experiment
After 600 trails people were able to divide their attention (practice allowed for this)
Automatic processing
Occurs without intention and only uses some of a person’s cognitive resources
Divided attention-distractions while driving
100 car naturalistic driving study:
- video recorders placed in cars
- risk of accident is four times higher when using a cell phone
Strayer and Johnston (2001):
- simulated driving task
- participants on cell phone missed twice as many red lights and took longer to apply breaks (same results for hands free cell phones)
Inattentional blindness
A stimulus that is not attended is not perceived, even though a person might be looking directly at it
Inattentional blindness experiment
One green horizontal line and one blue vertical line
Participants had to say which was longer
On the 6th trial a small square is included in the display (participants couldn’t recall seeing it)
Change blindness
If shown two versions of a picture, differences between them are not immediately apparent
-task to identify differences requires concentrated attention and search
This is because we are paying more attention to the movement between the pictures
Change detection experiment
-Person in gorilla suit that walked through basketball game
-flicks versus no flicks
Grey screen between two images (flick) result in less right and takes longer
No flicker gives motion signal that allows you to detect change easily
Explanation of change blindness
Attention is needed to see change
-without it observers are change blind
Our actual sensory representations are sparse
-little is retained over time
In everyday life we usually see ______
Change
- if something changes, creates a motion signal
- motion is an exogenous cue (draws attention)
- if something interferes with drawing of attention (flicker) then Attention doesn’t go to change
Binding
The process by which features such as colour, form, motion, and location are combined to create our perception of a coherent object
Refers to a FIT
FIT can predict
Illusory conjunctions
Physiology of Attention
Attention enhances neural responding
Attentional processing is distributed across a large number of areas in the brain
fMRI to detect cortical activity during a search task
Showed that attention to an expected direction of motion caused brain activity to increase in a number of brain areas
E.g. person looking at a patterned disc
Attentional blink
Visual search reflexes the spatial properties of our attention and attentional blink reflexes the temporal properties of our attention
Attentional blink experiment
Raymond et.al (1992)
Experimental condition: identify the white target and report whether there is the probe X by pressing a button
Control condition: only report whether there is the probe X. In half trials, there was no probe X
Attentional blink experiment results
For control condition subjects correctly detected the probe on 85% trials
For the experimental condition the detection of the percentage correct dropped below 60%
This is because when two targets are presented within 500 ms of each other, subjects are unable to report the second target
Attentional blink is not the result of perceptual memory or response output limitation but because allocation of attention to the first object leaves less attention for the second
As temporal separation ______, identification of the second letter ______
Increases
Improves
