Shifting Spatial Attention
 
 
 
Explain
Glossary

Chapter 8. Shifting Spatial Attention

Demonstration 8.3
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You must read each slide, and complete any questions on the slide, in sequence.
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Shifting Spatial Attention

Participate in an experiment aimed at assessing how long it takes to shift your attention.

CLICK ANYWHERE TO BEGIN

Road signs direct our attention to upcoming changes in the road or a potential danger. Our visual system makes use of these sorts of attentional cues to speed up our responses to those conditions.
[Photo: © Jetta Productions, Inc./Spaces Images/Corbis.]

How Does the Locus of Attention Affect the Time Needed to Detect Visual Stimuli?

Attentional cuing—providing a cue about the location of an upcoming target stimulus—can be used to examine how the spatial location of a person's attention (the locus of attention) affects the speed with which the person can become aware of the target and respond to it.



In a typical experiment (Posner et al., 1978), the participant was instructed to fixate on a point at the center of a visual display (Time 1 in Figure 1a). One of three cues then appeared in the display for one second (Time 2): a left- or right-pointing arrow indicated that the participant should direct her attention to the corresponding side of the fixation point, because she'd been told that a target was likely to appear in that location; a plus sign was a neutral cue, indicating that the target was equally likely to appear in either location. Regardless of where she directed her attention, the participant was required to keep her gaze on the fixation point. The target then appeared (Time 3), and the participant had to press a button as soon as she saw it.

When the cue indicated that the participant should direct her attention to the left or the right, the target appeared on that side in 80% of the trials (these were called valid cues) and on the other side in 20% of the trials (invalid cues); when the cue was neutral, the target appeared equally often on either side.



Figure 1b shows that the time required to press the button—the response time—was significantly faster when the target followed a valid cue than when it followed an invalid cue, with the response time to targets following neutral cues somewhere in between. This indicates that detecting the target is significantly faster when it appears in an attended location than when it appears in an unattended location. It's as if an "attentional spotlight" is directed to the cued location, and this speeds perception.
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In this demonstration, you’ll be a participant in an experiment modeled after one that was conducted in 1978.

The original experiment measured differences in response time to stimuli in attended versus unattended locations. The results led the researchers to conclude that people can move their visual attention around a scene without moving their eyes and that people respond faster to stimuli that appear in an attended location. You’ll see whether your own results support those conclusions.

Completing the experiment will take you about 10 minutes.

In each trial of the experiment:

1. A cue will appear at the center of the display. The cue will be an arrow or a plus sign.

2. A short time later, a target will appear to the left or the right of the cue. The target will be a black square.

3. Press the spacebar as soon as you see the target in your peripheral vision, without moving your eyes from the cue.

On trials where the cue is an arrow (like the one below), you can expect the target to appear on the side where the arrow is pointing. (It’s much more likely, but not certain, to appear on that side of the arrow than on the other side.)

On trials where the cue is a plus sign (like the one below), you can’t predict where the target will appear—it’s as likely to appear on the left of the cue as on the right.

On all trials, regardless of where the target appears, you must press the spacebar as soon as you see the target, because the computer will be measuring your response time—the time from the moment when the target appears to the moment when you press the spacebar.

Throughout the experiment, you must keep your eyes fixed on the center of the display (the location occupied by the black circle below).
Remember, during the experiment, you must keep your eyes fixed on this location, at the center of the display, where the cue will appear.
During the experiment, keep your eyes fixed on this location, at the center of the display.
During the experiment, keep your eyes fixed on this location, at the center of the display.
During the trials, remember to keep your eyes fixed on the location of the cue, at the center of the display.
PRESS SPACEBAR TO CONTINUE
PRESS SPACEBAR TO CONTINUE
PRESS SPACEBAR TO CONTINUE
PRESS SPACEBAR TO CONTINUE
PRESS SPACEBAR TO TRY A FEW PRACTICE TRIALS
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Before each trial, you’ll see this fixation circle at the center of the display for 1 second, before the cue appears. Remember to keep your eyes fixed on this location.
PRESS THE SPACEBAR TO INITIATE THE SIX PRACTICE TRIALS

PRESS SPACEBAR TO CONTINUE
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Now it’s time to begin the actual experiment—120 trials like the practice trials.

It should take you 5–10 minutes to complete all 120 trials.

Be sure to complete all the trials—if you don’t, you won’t be able to see your results.

The computer will be measuring your response time in each trial, so be sure to press the spacebar as soon as you see the square target.

Throughout the experiment, you must keep your eyes fixed on the center of the display (the location occupied by the black circle below).
PRESS SPACEBAR TO BEGIN
You must select an answer and then click SUBMIT before you can click proceed to the next screen
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PRESS THE SPACEBAR TO START
Trial 1 of 120

PRESS SPACEBAR TO CONTINUE
Trial 1 of 120
You must select an answer and then click SUBMIT before you can click proceed to the next screen
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The graphs below show the response times on trials where the cue (an arrow or a plus sign) was valid, invalid, or neutral:

   •  80% of the arrow cues were valid (the arrow pointed to the side where the target appeared).

   •  20% of the arrow cues were invalid (the arrow pointed away from the side where the target appeared).

   •  The plus sign cues were neutral (the target appeared to the left of the cue 50% of the time and to the right 50% of the time).

The graph on the left is based on the results from the original 1978 experiment and reflects the typical group results from this type of experiment. The graph on the right shows your median response time for each type of cue (valid, invalid, or neutral). In both graphs, a lower response time means a faster response.

Typical group results
Typically, participants respond fastest after valid cues, slower after neutral cues, and slowest after invalid cues.
Your results
How do your results compare to the typical group results? There are many reasons why your results might differ, including the relatively uncontrolled conditions in this demonstration.

Your results cannot be displayed because you didn't complete all 120 trials.

If you want to complete all the trials and see your results, click FINISH.

explain_text

How Does the Locus of Attention Affect the Time Needed to Detect Visual Stimuli?

Attentional cuing—providing a cue about the location of an upcoming target stimulus—can be used to examine how the spatial location of a person's attention (the locus of attention) affects the speed with which the person can become aware of the target and respond to it.

In a typical experiment (Posner et al., 1978), the participant was instructed to fixate on a point at the center of a visual display (Time 1 in Figure 1a). One of three cues then appeared in the display for one second (Time 2): a left- or right-pointing arrow indicated that the participant should direct her attention to the corresponding side of the fixation point, because she'd been told that a target was likely to appear in that location; a plus sign was a neutral cue, indicating that the target was equally likely to appear in either location. Regardless of where she directed her attention, the participant was required to keep her gaze on the fixation point. The target then appeared (Time 3), and the participant had to press a button as soon as she saw it.

When the cue indicated that the participant should direct her attention to the left or the right, the target appeared on that side in 80% of the trials (these were called valid cues) and on the other side in 20% of the trials (invalid cues); when the cue was neutral, the target appeared equally often on either side.

Figure 1b shows that the time required to press the button—the response time—was significantly faster when the target followed a valid cue than when it followed an invalid cue, with the response time to targets following neutral cues somewhere in between. This indicates that detecting the target is significantly faster when it appears in an attended location than when it appears in an unattended location. It's as if an "attentional spotlight" is directed to the cued location, and this speeds perception.
You must select an answer and then click SUBMIT before you can click proceed to the next screen.
test_single_choice

Select your answer to the question below. Then click SUBMIT.

This graph shows a typical pattern of results from an attentional cuing experiment like the one in this demonstration. What do these results imply about response times and the locus of attention?

A.
Invalid cues are associated with faster response times.
B.
Response times aren't influenced by the locus of attention, except when cues are neutral.
C.
If people aren't attending to any particular location where a target might appear, their response time will be longer than if they are attending to a particular location but the target doesn't appear there.
D.
People are able to respond more quickly to targets in attended locations than to targets in unattended locations.
Correct! Click EXPLAIN if you want to review this topic.
Incorrect.
The correct answer is D.
Click EXPLAIN if you want to review this topic.
You must select an answer and then click SUBMIT before you can click proceed to the next screen.
test_single_choice

Select your answer to the question below. Then click SUBMIT.

In an attentional cuing experiment like the one in this demonstration, what do you think the results would be if the arrow cues were as neutral as the plus sign—that is, if the target appeared equally often on either side of the arrow regardless of which way the arrow was pointing—and if participants were told beforehand that this would be the case?

A.
The results would be the same as the typical results.
B.
All reaction times would be much slower, but the validly cued targets would still be detected more quickly, and the invalidly cued targets less quickly, compared to the neutral targets.
C.
There would be very little difference in response times after valid, invalid, and neutral cues.
D.
The pattern of results would be inverted from the typical results: participants would, on average, respond fastest after invalid cues and slowest after valid cues.
Correct! Click EXPLAIN if you want to review this topic.
Incorrect.
The correct answer is С.
Click EXPLAIN if you want to review this topic.
You must select an answer and then click SUBMIT before you can click proceed to the next screen.
test_single_choice

Select your answer to the question below. Then click SUBMIT.

In attentional cuing experiments like the one in this demonstration, the cue is presented about 1 second before the target appears. How do you think the results would be affected if the cue and the target were always presented simultaneously?

A.
The results would be the same as the typical results.
B.
All reaction times would be much slower, but the validly cued targets would still be detected more quickly, and the invalidly cued targets less quickly, compared to the neutral targets.
C.
There would be very little difference in response times after valid, invalid, and neutral cues.
D.
The pattern of results would be inverted from the typical results: participants would, on average, respond fastest after invalid cues and slowest after valid cues.
Correct! Click EXPLAIN if you want to review this topic.
Incorrect.
The correct answer is C.
Click EXPLAIN if you want to review this topic.
You must select an answer and then click SUBMIT before you can click proceed to the next screen.
test_single_choice

Select your answer to the question below. Then click SUBMIT.

The graph on the left shows a typical pattern of results from an attentional cuing experiment like the one in this demonstration. What would be the most likely explanation for a pattern like the one in the graph at the right?

A.
For some reason, the participants had slower-than-normal responses.
B.
Participants weren't told beforehand that most of the arrow cues would be valid.
C.
The neutral cues were circles instead of plus signs.
D.
Participants completed many more than the usual number of practice trials before completing the test trials.
Correct! Click EXPLAIN if you want to review this topic.
Incorrect.
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Shifting Spatial Attention.
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