Week 9 - attention and workload

Question 1

define workload

Answer 1

Mental workload (referred to as just workload) is a general term used to describe the cost of accomplishing task requirements

Question 2

what does workload depend on?

Answer 2

1- Workload varies as a function of the task demands
placed on the human operator
2- The operator’s capacity to meet those demands

Question 3

what are three task demands

Answer 3

1- task difficulty
2- task priority
3- situation

Question 4

define operator capacity

Answer 4

• each operator has a supply of mental resources
• mental resources are limited in supply eg memory, planning, decision making
• Task performance generally improves as resources are directed to it
• Resources that are unused are referred to as ‘spare
  capacity’

Question 5

overload vs underload

Answer 5

• Generally, the focus is on the detrimental effects of overload (e.g. excessive workload)
• However underload (e.g. sustained low workload) is
  just as much of a problem

Question 6

what does underload cause

Answer 6

(1) Increased fatigue
(2) Lower task engagement
(3) Lower vigilance
(4) Generally reduces operators capacity to deal
with the unexpected (spare capacity)

Question 7

what are three reasons to why you measure workload

Answer 7

Workload prediction
• To maintain workload within acceptable limits
Equipment assessment
• Optimize the system to suit operator
Choose the right operators
• Employee selection or further training

Question 8

explain workload prediciton

Answer 8

Safety
• Often relies on predicting workload ahead of time
• When will an operator struggle?
Change management:
• Know in advance what effect
changes will have

Question 9

explain equitment assessment

Answer 9

Designers may want to know what workload will be at
the design, production, or usage stages
• Identify problem areas where performance may
decline
• Compare workload between multiple systems

Question 10

explain choosing the right operators

Answer 10

• Equipment design focuses on controlling task demands, but operator selection focuses on controlling operator capacity
  • Can train to improve some capacity, but only up to a
  point (and it may not be cost effective)

Question 11

what are three major categories of workload measures?

Answer 11

1. Performance
2. Subjective
3. Physiological

Question 12

what are two ways performance can be divided into?

Answer 12

• primary task measures

- secoundary task measures

Question 13

what is primary task performance advantages

Answer 13

• Workload reflected directly by performance outcome
• Non-invasive and non-interfering
• Tracks changes in workload dynamically. (i.e., as
performance proceeds)
• Uncontaminated by memory issues

Question 14

what is primary task performance disadvantages

Answer 14

• Mental workload is not the only thing that can
influence performance
• Doesn’t take effort into account
• Might not always have the technology or interface
available to monitor performance

Question 15

what is a secondary task purpose and what does it measure?

Answer 15

• To measure the spare capacity not being
  used by the primary task
  • Usually, an increase in primary task workload is
  associated with a decrease in secondary task perf.
  • Potential measures including: Rhythmic tapping task, Probe reaction tasks, Auditory monitoring

Question 16

what is secoundary task performance advantages

Answer 16

• The same secondary task can be used with very
different primary tasks
• There are a collection of available (and validated)
secondary tasks
• Provide a measure of space capacity
• Useful when there is little primary task data available
(e.g. monitoring jobs, baggage scanner)

Question 17

what is secoundary task performance disadvantages

Answer 17

• Only relevant when secondary task taps into the
same resources as the primary task
• It adds in another task to the work environment (could increase workload)
• Can interfere/interrupt primary task

Question 18

what are subjecive measures

Answer 18

Where you ask someone to quantify their personal
experience of workload
• Dimensionality (single or multiple)
• Evaluation (absolute or relative)
• Immediacy (when queried?)

Question 19

what is an example of a subjective measure

Answer 19

NASA Task Load Index (NASA-TLX

Question 20

what are advantages of subjective measures

Answer 20

• Cheap and simple to administer
• No need to interfere with primary task
• Reasonably good reliability and validity
• NASA-TLX has a huge literature available for
comparison

Question 21

what are disadvantages of subjective measures

Answer 21

• People aren’t always aware of workload
• People find it difficult not to baseline their workload
• Not sensitive to moment-to-moment changes

Question 22

what are physiological measures

Answer 22

• The assumption is that biological functions can
reflect mental work done.
• Popular measures include:
- Cardiovascular
- Ocular
- Brain activity

Question 23

explain cardiovascular physiological measures

Answer 23

• Heart-rate variability shown to increase with workload
• Particularly relevant to emotional stress
• Potential issues:
• Need to establish a baseline
• Quite a range due to individual differences
• Only sensitive when stress is involved

Question 24

explain ocular physiological measures

Answer 24

• Pupil diameter increases with workload
• Visual scanning patterns and pathways change with
workload
• Length of time spent fixating on items changes with
workload

Question 25

explain brain activity physiological measures

Answer 25

• It is intuitive that brain activity will reflect mental workload • Brain activity sensitive to different kinds of cognitive demands (e.g. memory, vigilance, flexibility, etc.) • Measures: Electroencephalogram (EEG), Eventrelated potentials (ERP), and Cerebral blood flow

Question 26

advantages of physiological measures

Answer 26

* Provide a relatively continuous measure over time * Objective * Many different techniques available

Question 27

disadvantages of physiological measures

Answer 27

* High cost * Often obtrusive * Cannot be used to determine how the operator feels about the task (can be important)

Question 28

Explain attention in mutiple resource theory

Answer 28

• Can be directed voluntarily • Attending to one thing often excludes others from processing • Can be divided, but not without cost

Question 29

Explain resources in multiple resource theory

Answer 29

* A general term covering resources used to perform a task | * From the lecture on errors:

Question 30

why do errors occur in mutpile resource theory

Answer 30

* Selective attention * Working memory capacity * Long term memory limited on storage and retrieval * Decision-making biases

Question 31

what is multiple resource theory

Answer 31

1. There is a common, finite pool of resources that can be flexibly allocated to tasks 2. Allocating more resources to a task speeds up the rate of processing of that task 3. The quantity of resources made available can be increased or decreased

Question 32

what happens if two tasks are similar - multiple resource theory

Answer 32

- If two (or more) tasks are similar they will draw on a common resource pool • This will affect performance negatively - If the two (or more) require different resources, then performing the tasks at the same time will have little negative consequence

Question 33

Stage 1- Stages of processing (MRT)

Answer 33

1- perception 2- cognition 3- response

Question 34

Stage 2- Codes of processing (MRT)

Answer 34

- spatial | - verbal

Question 35

Stage 3- Modalities (only relevant for perception stage):

Answer 35

* Auditory perception (e.g. listening to radio) | * Visual perception (e.g. looking for a sign)

Question 36

Visual channels (only relevant in visual modality)

Answer 36

* Focal channel (focus of attention, e.g. car in front) | * Ambient channel (peripheral vision, e.g. cars on either side)

Question 37

what three resources do you need to drive safetly

Answer 37

- cognitive - manual - visual

Question 38

what are the 4 stages resources can be shared across

Answer 38

1- stages 2- codes 3- modalities 4- channels

Question 39

define interruption

Answer 39

An interruption involves the primary task being suspended | while the secondary task is completed

Question 40

define distraction

Answer 40

``` A distraction (or multi-tasking) is performing both at the same time (or more accurately, rapid task switching) ```

Question 41

what are the costs of an interruption

Answer 41

• Memory: We form PM intentions when interrupted, and these degrade over time • Warning: Sometimes there is little/no time to form intention • Duration: Length of interruption, frequency of interruptions • Content: Interruptions more disruptive if similar

Question 42

what is a prospective memory requirement (PM)

Answer 42

- holding an intention is costly - the longer you have to hod it the poorer the retrieval - Primary task performance slower and less accurate (i.e. more errors) when primary task is resumed

Question 43

how to solve the problem

Answer 43

1. Aiding the Interrupt task alert stage: Provide information about the urgency of the interruption 2. Aiding the Disengagement stage: Reduce the to-be-remembered information load 3. Aiding the Resumption stage: Upon resumption, use memory aids created