Transcript More….attention - Villanova University

Limits on Ability to Perform
Different Tasks Simultaneously
Two basic issues:
1. Task-Specific Resources
2. Task-Independent Resources
Verbal Judgments
Interferes
Verbal Responding
Spatial Judgments
OK!
Interferes
Spatial Responding
Task-General Resources
Reaction Time Tasks
• Simple Reaction Time (~200 msec)
• Choice Reaction Time (300 msec ++)
Present Stimulus
Subject Responds
Reaction Time
stimulus
stimulus
stimulus
1
2
3
button1
button2
stimulus
stimulus
stimulus
A
B
C
button1
button2
Task 1
button3
Task 2
button3
Processing Stages in Choice RT Tasks
Present Stimulus
Subject Responds
Reaction Time
Perceptual
Processing
Decision/
Response Selection
Response
Production
Question: Can people do two tasks this simple at one time?
Psychological Refractory Period experiment
(Telford, 1931)
Present Stimulus 1
Response 1
Reaction Time 1
Present Stimulus 2
Delay
Reaction Time 2
Response 2
There is dual-task interference!
Reaction
Time
Reaction Time 2
Reaction Time 1
(Same results for almost all task pairs,
whether similar or not.)
PRP
effect
Delay from S1 to S2
“Psychological Refractory Period”
Stimulus 1
Response 1
Reaction Time 1
Response 2
Stimulus 2
Delay
Reaction Time 2
Total Time for both task
Total Time < (Task1 + Task2)
Response Selection Bottleneck Model
• All task elements can occur in parallel except for
response selection
Perceptual
Processing
Delay
Response
Selection
Perceptual
…”slack”...
Processing
Response
Prod.
Response
Selection
Response
Prod.
Response selection for Task 2 has to
wait until response selection for task 1
is completed
(e.g. Pashler, 1991)
stimulus
stimulus
stimulus
A
B
C
button1
button2
stimulus
stimulus
stimulus
A
B
C
button1
button2
Task 2
easy mapping
button3
Task 2
hard mapping
button3
Easy Response Selection
Perc.
Resp. Sel.
Perc.
Resp.
Resp. Sel.
Resp.
Delay
Hard Response Selection
Resp. Sel.
Perc.
Perc.
Delay
Resp.
Resp. Sel.
Resp.
Reaction Time 1
Delay from S1 to S2
Reaction Time 2
Delay from S1 to S2
Reaction Time 1
Hard task 2 response selection =
Easy task 2 response selection
Delay
Reaction Time 2
Hard response task 2 selection
Easy task 2 response selection
Delay
Easy Task-2 Perception
Perc.
Resp. Sel.
Perc.
Resp.
Resp. Sel.
Resp.
Delay
Hard Task-2 Perception
Resp. Sel.
Perc.
Perc.
Resp.
Resp. Sel.
Resp.
Delay
The increased perceptual difficulty gets absorbed in the slack time, with
no extra-cost for the secondary task
Reaction Time 1
Delay from S1 to S2
Reaction Time 2
Delay from S1 to S2
Reaction Time 1
Hard task 2 percept. =
Easy task 2 percept.
Delay
Reaction Time 2
“Absorption into slack”
Delay
Hard task 2 percept.
Easy task 2 percept.
With no response selection bottleneck…
Easy Response Selection
Perc.
Resp. Sel.
Perc.
Resp.
Resp. Sel.
Resp.
Delay
Hard Response Selection
Resp. Sel.
Perc.
Perc.
Delay
Resp. Sel.
Resp.
Resp.
Reaction Time 1
Hard task 2 response selection =
Easy task 2 response selection
Delay
Reaction Time 2
Hard response task 2 selection
Easy task 2 response selection
Delay
If there is absolutely no bottleneck…then there will be a constant difference
between easy and hard task 2 RT across all delays…in addition, there should
be no rise in RT at even the shortest delays...