1. Chapter 3
Divided attention

2.  Introduction
 Dual task experiments
 Theories
 Single or multiple processors?
 Summary

3. Introduction
 Doing two things at once
 Everyday experience
 Dual tasks

4. Dual task experiments
 Eysenck & Keane(1995) have identified
three major factors that affect the
ability to do two(or more) tasks at once
 Task similarity
 Task difficulty
 Practice

5. Task similarity
 Allport et al.(1972):shadow prose and
learn a list of words(recall)
 Present to the other ear(poor)
 Print on a screen
 Present as pictures on a screen(very
good)
 It is a difficult concept to define

6. Task difficulty
 inter-individual
 intra-individual
 Combine with a second task

7. Practice
 Spelke et al.(1976):write down dictated
words while reading short stories
 Reasons
1. Reduce the amount of resource
2. Help participants learn strategies

8. Theories

9. Central capacity theory
 Kahneman(1973)
 Attention as a skill rather than a process
 Mental effort=tasks require different
processing capacity
 The difficulty of the task & the degree of
practice

10. Central capacity theory
Kahneman(1973) Arousal
central processor
Available
Capacity
Enduring
Dispositions
Allocation
Policy
Momentary
Intentions
Evaluation
Possible Responses
of Demands
on Capacity
Response

11. Evaluation
 Task difficulty, the role of practice and
arousal
 Problems
1. The limits of capacity
2. Does not explain the strong influence of
similarity

12. Central capacity interference theory
 Norman and Bobrow(1975)
 Resource-limited & data-limited

13. Evaluation
 Cherry(1953)
 Failure to predict performance of tasks in
experiments
 Non-falsifiable

14. Multiple channel theories
A limited capacity model
A central processor A single filter
Explaining the complex Dealing with all
nature of attention (Neisser, attentional tasks?
1976 ; Allport, 1993) ?
Dealing with many different types of task
required by an attentional system ?
•It is difficult to see how the neurology of the brain could
produce a system of processing a capacity
(Hampson and Morris,1996)

15. Allport – modules of attention
 Attention consists of a number of specialised
modules (Allport, 1980,1983)
 Each module deal with a different ability or skill
 Each module has its own resources and a limited capacity
 Wicken, 1984
 Different modules may deal with different aspects of a
task
 Modules exist for input/processing/output mode

16. (1)Listening to (2)List of words
a massage to be learned
(3)Shadowing
message
(1)Listening to
a massage
(1)List of pictures
(3)Shadowing to be learned
message

17. Evaluation of module theory
 To explain the effects of similarity in dual task
experiments
(Allport et al.,1972
Treisman and Davies, 1973)

18. Evaluation of module theory
 The fundamental assumptions of cognitive
neuropsychology
 Relatively independent cognitive processors or
modules
 Each one can function to some extent in
isolateion
 Brain damage (Eysenck and Keane, 1995)
 Only some of these modules are impaired

19. Evaluation of module theory
 Problem 1  Problem 2
 It doesn’t specify the  How the modules work
number of modules together?
 What types of modules  How the modules are
they are? co-ordinated
 The theory is therefore  Enough practice
non-falsifiable  The similar tasks can
work concurrently
 Competing for the
resources of one module
(Underwood, 1974;
Spelke et al., 1976)

20. Multiple Resource Theory
 Navon & Gopher (1979)
- specialized “mental resources” (like modules)
- performance can be traded (new concept)
- supply and demand
 Good explanation of effect of task similarity
in dual task experiments
(Allport et al, 1972)

21. Multiple Resource Theory
Input Processing Response
Information
• Stimuli • Transformation • Output

22. Multiple Resource Theory
Saws Lathes
Dri
ll
Drill Finished
Raw Material
Product

23. Multiple Resource Theory
 Dawson and Schell (1982)
- Shadowed a message
- Classically conditioned word in non-attended ear
(left or right)
- Conditioning = paired with mild electric shock
- Subsequent recognition = autonomic nervous system
response
- Left vs. right hemisphere - Left for speech reception
and production
- Right for speech analysis
- Automated response to unattended message in left
ear but not right ear

24. Multiple Resource Theory
 Payne and Wenger (1998)
- Single capacity model
= response in both ears or neither
- Multiple resource model
= response to each ear differently
- Not able to detect unattended message in right ear
- Left hemisphere is for speech reception and production,
and primary task (shadow message) takes priority
- Not enough resources to analyze unattended message at the
same time

25. Multiple Resource Theory
 Failure to specify number of resources
 How the multiple resources work together
 Attentional processes highly integrated
HOW?

26. Single or Multiple Processors?
 Flaws with both models
 Single capacity models fail to account for effect of
similarity in dual task experiment
 Multiple capacity models fail to explain how
different parts of attention work together

27. Single or Multiple Processors?
 Baddeley (1986)
- Synthesis theory
- combine features of both approaches
- central, limited capacity processor
(from central capacity theory)
- modality-specific processing systems
(from modular or multiple resource theory)

28. Single or Multiple Processors?
Central Executive
(central, limited capacity
processor)
Modality-specific
processing systems
Visuo-
Spatial Phonological Loop
Sketchpad

29. Single or Multiple Processors?
 Good compromise?
 Still got problems
 Role of the central executive
 How different components are integrated

30. Summary
 Divided attention
- studied using dual task experiments
- influenced by task similarity
task difficulty
task practice

31. Summary
 Kahneman
- single, limited capacity central processor
- explains effect of task difficulty and practice
- does not explain effect of task similarity on
performance

32. Summary
 Norman and Bobrow
- modified version of central capacity model
- tasks: resource-limited
data-limited
- more flexible model
- problem: non-falsifiable

33. Summary
 Allport
- modular approach
- different modules with individual resources &
capacities
- better at explaining influence of task similarity
- supported by findings of cognitive neuropsych
- problem: does not specify number of modules
how modules are integrated

34. Summary
 Navon and Gopher
- multiple resource theory
- similar to Allport
- similar strength and weakness

35. Summary
 Baddeley
- synthesis theory
- central limited capacity processor
- individual processors for different tasks

36. THANKS FOR
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