1. CS 522: Human-Computer Interaction Attention and Mental Workload
Dr. Debaleena Chattopadhyay
Department of Computer Science
debaleena.com

2. Attention Attention was of interest around the turn of 20th century.
It lost favor during the first half of the 20th century, because it was identified with unseen mental events.
How was it restored?

3. What abilities intrigued them?
Applied psychologists in England restored attention as a legitimate research topic.
What abilities intrigued them?
Air traffic controllers abilities to divide attention among multiple interests.
Radar operators ability to maintain vigilance while monitoring screens for enemy subs.

4. Models of attention Models of Attention Bottleneck Models
Resource Models
Early Selection
Late Selection
Single Resource
Multiple Resources

5. Bottleneck model of attention
Identifies a stage in the information processing sequence.
At that stage the amount of information that can be attended to is limited.
FT – promotion of desired stimuli
FAT – can be adjusted on the basis of relatively gross physical characteristics:
i.e. Spatial location or vocal pitch
Allowing only one source of input to enter the identification stage.
Here there is a notice of physical features of unattended message
speech v non speech
male v female voice
Semantic features tend to go unnoticed
English sentences v jumbled words
word meaning, etc.
Although again words leak in; a person name is attended to (“cocktail party” effect)

6. Attentional Filter
Stimuli enter a central processing channel one at a time.
Filtering of extraneous information happens before identification.
Thus, processing of distracters is blocked.
Limitations?
Leaks are not accounted for.

7. Attentional Attenuation
Early filter serves only to attenuate the signal of an unattended message rather than to block it entirely.
Limitations?
Not easily testable

8. Broadbent’s Filter Model

9. Resource model of attention
Views attention as a limited-capacity resource that can be allocated to one or more tasks.
Unitary-Resource Models
Attention is a single limited capacity resource.
It can be applied to various tasks.
Performance declines if capacity is exceeded

10. Unitary-resource model
Representative of attentional limitations arising from a limited capacity of resources for mental activity as apposed to focusing on a specific location in the information-processing sequence.
Noting that performance suffers when resource demands exceeds the supply.
Unitary-resource model

11. Posner and Boise (1971) RT test results
Primary and secondary tasks
Where a letter was shown and another letter shown 1 second later, as well audio tones are played.
The participant was to determine if the letters where the same or different.
Test is setup to determine difficulty of tasks and to predict when operator performance will begin to suffer.

12. Resource model of attention (cont..)
Multiple-Resource Models
Distinct subsystems each have their own limited resources.
Developed because the performance decrement for multiple tasks often depends on the stimulus modalities and the responses required for each task.

13. Wickens’ (1984) 3D Model
Shows stages of processing (encoding, central, and response), codes (verbal and spatial), input (visual and auditory) and output (manual and vocal) modalities.
Assumes two tasks may be performed more efficiently using separate pools of resources.
Changes in difficulty in one task should not affect the performance of the other task.

15. Modes of attention What are the three modes of attention? Selective
Divided
Arousal and Vigilance

16. Selective Attention Selective attention is a component of many tasks.
One way of attending to visual stimuli is through positioning of the eyes.

17. Selective attention experiment:
Read the bold print.
Somewhere Among hidden the in most the spectacular Rocky Mountains cognitive near abilities Central City is Colorado the an ability old to miner select hid one a message box from of another. gold. We Although do several this hundred by people focusing have our looked attention for on it, certain they cues have such not as found type it style.

18. What can you recall about the sentence?

19. Results
Among the most spectacular cognitive abilities is the ability to select one message from another.
We do this by focusing our attention on certain cues such as type style.

20. What can you recall about the other sentence?

21. Results
Somewhere hidden in the Rocky Mountains near Central City, Colorado, an old miner hid a box of gold. Although several hundred people have looked for it, they have not found it.

23. Change Blindness
Change blindness refers to a person’s inability to detect gross or striking changes in a visual scene.

24. Divided Attention Attending to several sources of input simultaneously
Each task does not have to have the same priority.

25. Arousal and Vigilance Arousal Vigilance
Alertness, readiness to respond
Arousal influences attentional ability and attentional resources available.
Performance deteriorates at high arousal levels.
Doing boring tasks for long periods of time lowers arousal.
Vigilance
Alert watchfulness

26. The Yerkes–Dodson law (1908)

27. Mental Workload Assessment
What is mental workload?
Workload is the total amount of work a person or group is to perform over a given period of time.
Mental workload – amount of mental work or effort necessary to perform a task.
By what techniques is mental workload assessed?

28. Mental Workload Assessment Empirical Techniques
Primary-task Measures
Secondary-task Measures
Psychophysiological Measures
Subjective Measures

29. Mental Workload Assessment Empirical Techniques
Primary-task Measures
Examine the performance of the operator or of the overall system.
Secondary-task Measures
Workload is assessed by the degree to which performance deteriorates in the dual task situation relative to when each task is performed alone.

30. Mental Workload Assessment Empirical Techniques
Psychophysiological Measures
Pupillometry
Heart rate
Event-related potential (EEG)
Limits?
Require sophisticated instrumentation
May interfere with task performance
Subjective Measures
Evaluate workload by operator judgment (e.g., NASA-TLX).

31. Project Discussions

32. To do: HW 1 DUE – Sep 14 Readings: None
Sign up for your proposal presentations – DUE next week
Slide credits: K. F. MacDorman, Proctor & Zandt