4 – Divided Attention divided attention trying to do two things at the same time Some dual tasks cause no interference. Example Walk and chew gum Some dual tasks cause interference. Example Drive and talk on cell phone. Question What kinds of tasks can be done concurrently without interference?
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4 – Divided Attention divided attention trying to do two things at the same time Some dual tasks cause no interference. Example Walk and chew gum Some.
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4 – Divided Attention
divided attention trying to do two things at the same time
Some dual tasks cause no interference.
Example
Walk and chew gum
Some dual tasks cause interference.
Example
Drive and talk on cell phone.
Question
What kinds of tasks can be done concurrently without interference?
Demo Task A = Rotate right arm clockwise.
Task B = Rotate left arm counterclockwise
A & B no interference
Demo Task A = Rotate right arm clockwise.
Task B = Rotate right leg counterclockwise
A & B interference
Typical Divided Attention Experiment
3 conditions: A only
B only
dual-task (A and B at the same time)
dual task interference occurs if
Performance on A is better during A-only condition than during dual-task.
or Performance on B is better during B-only condition than in dual-task.
Laws prohibiting cell phone use while driving (as of 2013)
For experienced drivers, hands-free phone banned in 0 states.
Handheld phones banned in 10 states (but not Florida).
Texting while driving is banned in 41 states, including Florida.
Common belief: Driving is unaffected by driver’s use of hands-free phone
Typical explanation. The two tasks are very dissimilar.
driving car visual, spatial, manual
talking on hands-free phone oral, verbal, auditory
Laws conform to this belief.
Use of handheld phones prohibited in many states.
Use of hands-free phones allowed in every state (as of 2011).
Does this make sense? Or do hands-free phones also cause interference?
Driver Distraction experiments
Task
Ss drive in simulators
Ss must avoid cars, pedestrians.
Typical Measures
Braking time
Number of collisions
Common Conditions
driving while talking on handheld phone
driving while talking on hands-free phone
driving while talking to passenger
driving while reading text
driving while composing text
driving intoxicated
Experiment: Effect of hands-free phone
Ss drove in simulator. During dense traffic, car in front stopped unexpectedly.
Sample result Brake Time (ms)
no distraction 933
talking on hands-free phone 1112
Conclusion
Interference is attentional – not just manual.
(Strayer et al., 2003)
Experiment: Hands-free phone vs. Intoxication
Ss drove in simulator. Car in front suddenly stopped.
One result:
Brake time (ms)
intoxicated (BAC 0.08%) 779
hands-free phone 849
(Strayer et al., 2011)
Experiment: Is hands-free phone worse than talking to passenger?
“… Passengers tend to adjust their conversation based on driving difficulty; often helping the driver to navigate and identify hazards on the roadway and pausing the conversations during difficult sections of the drive. By contrast, this real-time adjustment based upon traffic demands is not possible with cell phone conversations.”
Strayer and Drews (2006, p. 130)
Experiment
S drove in simulator; was asked to exit the highway at rest stop “about 8 miles away”
S listened to friend tell story
Result: Drivers who Missed the Exit
driving alone 4%
passenger conversation 12%
hands-free cell phone conversation 50%
(Drews et al., 2008)
Other findings from driver distraction studies:
Most Ss overestimate their ability to drive while using a hands-free phone.
Hands-free phone as bad as handheld phone
Four 1-minute videos (bottom of webpage)
www.psych.utah.edu/lab/appliedcognition/news.html
Strayer and his colleagues (2001, 2003, 2006, 2009)
During certain stage in completion of Task 2, progress completely stops.
Task 1 alone |------------------------------|
Task 2 alone |------------------------------|
500
Dual-Task
Task 1 |------------------------------|
Task 2 |------- wait -----------------------|
700
In other words, at some point, Task 2 must wait for Task 1.
Experiment
Ss saw between 1 - 6 “study letters” at rate of one per sThen Ss saw target letter.Ss hit yes or no key, depending on whether target was a study letter.
For target-absent trials, task included :
Perceive TargetMentally scan study letters, one at a timeSelect response (“no”)Produce response
Results: Each additional study letter increased RT by 38 ms
Conclusion : Ss “mentally scanned” letters at rate of one per 38 ms
(For complicated reasons, this interpretation is no longer popular.)
(Sternberg, 1966)
Bottleneck finding conflicts with traditional view of dual-task interference:
limited resource theory
tasks can be done concurrently and without interference if demand < supply.
A formal definition of the term “attention” is not presently available…
(Pashler & Johnston, 1998)
Demo Even two easy tasks can cause dual-task interference Easy: Pat head and stomachHarder: Pat head, rub stomach Easy: R hand CW, R foot CW. Harder: R hand CW, R foot CCW.
Sample Experiment
Ss shadowed 10 words presented to one ear.
At same time, S tried to remember 10 other items simultaneously.
1) seen as pictures
2) seen as words
3) heard as words (in other ear)
Then Ss tried to recall the 10 non-shadowed items.
Results
(3) was hardest; (1) was easiest.
Conclusion
Task similarity increases dual task interference.
(Allport, Antonis, & Reynolds, 1972)
Statistic
In 2009, cell phone use was a factor in 995 driving fatalities in US (NHTSA).