MENTAL WORKLOAD

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MENTAL WORKLOAD SITUATION AWARENESS

• Nantida Wisawayodhin M Sc. M.Erg.S.

Module Cognition and Information
Processing Course Human Centered Design
(HCD) SOAD, KMUTT
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OVERVIEW

• BTS redesign
• Trade-offs between principles and requirements
• Air crash error identification and solution
• Relationship between MWL and SA
• Situation Awareness (SA)
• Mental Workload (MWL)
• Case Study Three Mile Island
• Mid-term project

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BTS TICKETING MACHINE

• INTERFACE REDESIGN
• User types Novice, Occasional Expert
• Users Tourist, daily users, blind, deaf
• Objectives
• Buy a correct ticket for the right destination

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BTS TICKETING MACHINE

• Daily users (Experts)
• They are likely to use cards.
• They are likely to know the zone number and cost
  of their regular destinations
• Least group to worry about
• Occasional users
• Possibly use cards
• Likely to be familiar with the system
• Novice users
• Unlikely to know how the ticketing system works
• The user group to take into consideration the
  most when designing serf-service interfaces
• Blind and deaf
• May need to present information in an alternative
  mode

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TASK SEQUENCE
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MOVEMENT PATTERN
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PRACTICAL Issues

• Appearance
• Not attention catching no clear indication that
  it is a ticketing machine
• Design blends in with the environment
• Look like another advertisement board
• Task sequence
• Not clear where to start
• Too many sub tasks
• Does not fit user expectations (one-stop shop,
  take bank note)
• Design around system convenience than user
  convenience
• Memory Aid
• Step 1 is not the start point of the ticket
  buying process

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EXAMPLES OF APPLICABLE GUIDELINES

• Visually displayed memory aids should be used to
  replace a memory store with a physical store
  wherever this is necessary.
• The different problem solving strategies employed
  by experts and novices must be taken into account
  when designing for both types of users
• Consider design in guidance for the
  transformation of information from novice to
  expert by making expert paths visible to novices.
• Tasks that use verbal working memory are served
  best by auditory inputs and vocal outputs.
• Auditory presentation is not very effective when
  the message is long (gt5 unrelated words or
  letters). In such cases, text input should be
  used as well as or instead of speech.
• Exploit existing known mental models to help
  users to better understand the product more
  intuitively

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PRACTICAL Solutions

• Appearance
• Attention catching Clear information sign to
  indicate location of Ticket Machine
• Make it stand out and visible at the entrances
• Task sequence
• Reduce number of steps
• Make it a one-stop shop
• Design to take bank notes
• Design with user in mind
• Memory Aid
• Start step 1 where it should be at the map
• Blind users
• Use handrail or floor texture to indicate where
  to go
• Make use of vocal-auditory modality
• Use Brail language on buttons
• Provide staff assistance

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MOVEMENT PATTERN
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TRADE OFFS

• Between design principles and HF principles
• Aesthetics/trend vs. ease of use
• Between engineering requirements and HF
  principles
• Optimum condition for machine its performance
  vs. optimum condition for the operators and their
  performance
• Between safety requirements and HF principles
• Protection vs. visibility or ease of movement
• Between HF principle and HF principle
• Providing situation awareness vs. avoiding
  distraction

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TRADE OFFS Design Principles
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TRADE OFFS Design Principles
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TRADE OFFS Safety requirement

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TRADE OFFS Safety requirements
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TRADE OFFS HF Principles
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MIDLAND AIR CRASH

• A crash of Midlands flight 092 in June 1989 was
  initiated by a mechanical failure in the left
  engine, which had escalated due to a misdiagnosis
  of the problem by the pilot and co-pilot,
  resulting in a shutdown of the good engine. A
  total of 47 lives were lost with numerous
  injuries.

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MIDLAND AIR CRASH

• Sequence of events
• Please see the printed table provided

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MIDLAND AIR CRASH

• Active failure
• KB and RB mistakes - misdiagnosis of engine
  failure
• SB lapse failure to complete situation check
  procedure
• Latent failure
• Faulty design of the left engine
• Poor display design
• The lack of communication of the changes made to
  Boeing 737
• Inadequate training
• Lack of communication procedure between pilot and
  air crew during emergencies
• Human error is the tip of the icebergs!

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MIDLAND AIR CRASH

• Changes made to the Boeing 737
• Please see the printed table provided

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MIDLAND AIR CRASH

• Loss of situation awareness (SA)
• Applying incorrect mental model
• KB and RB mistakes
• Fast moving, dynamic and complex system
• Errors difficult to detect and correct
• Increase in mental workload (MWL)
• No longer can make use of available knowledge
• KB performance heavy demand on WM and mental
  resources
• More difficult to follow the situation and
  predict the outcome of actions taken
• The new design of Boeing 737 did not take human
  behaviour into consideration

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MIDLAND AIR CRASH

• Issue Engine never tested in flight, only bench
  tested in laboratory. Flight test was not
  mandatory
• Solution Manufacturers now must flight test all
  new engines
• Issue Flight simulator training none, so when
  pilots meet problems it is for real
• Solution Now mandatory flight simulation
  training for all new designs and upgrades
• Issue Cockpit displays being small and difficult
  to use are difficult to interpret
• Solution Boeing redesign cockpit displays for
  ease of interpretation for pilots.
• Issue Lack of communication between pilots and
  air crew during emergency
• Solution Full communication between pilot and
  air crew

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MIDLAND AIR CRASH

• Difficulty issue Bad timing of
• Communication between ATC and pilot
• Communication between train driver and signaller
• Difficult to solve, but one solution
• Role swap to become aware of the others tasks
• Encourage communication and exchange of knowledge
  between the roles

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MWL SA

• The two concepts are intertwined.
• The interaction between external cues and the
  internal knowledge
• Internal Skill, expertise, experience, schema,
  mental models
• External Available information from the external
  world in order to access correct mental model and
  make informed decisions
• Maintenance of the dynamics of the situation
  mentally requires mental resources
• Access of a correct mental model reduces the
  competition for the same mental resources for
  real-time decision making and problem solving and
  SA
• Novel situations or novices unable to make use of
  existing knowledge (mental models) resort to KBP
  to maintain SA and to make decisions high
  competition of the same mental resources high
  MWL

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INFORMATION PROCESSING SA

• The combined operations in perception, working
  memory, and long-term memory, that enable the
  decision maker to entertain hypotheses about the
  current and future state of the world

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MODEL OF HUMAN INFORMATION PROCESSING
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SITUATION AWARENESS

• Closer to home examples
• Doctor appointment scenario
• Indicating when wanting to turn or change lanes

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SITUATION AWARENESS

• Why do we concern ourselves with SA?
• To better understand the causes of accidents and
  disasters
• To design displays and systems to support SA

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BREAK

• 15 MINUTES

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SA INTRODUCTION

• Studies found that people are generally able to
  physically perform complex tasks and deciding on
  appropriate actions
• But tend to find it difficult to understand what
  is going on in the situation
• Developing and maintaining situation awareness is
  the critical and most important component of
  effective decision making
• A vast proportion of our everyday problem solving
  and decision making performance is spent on
  developing SA and keeping it up to date in the
  rapidly changing environment

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SA INTRODUCTION

• All of the incoming data from the many systems,
  the outside environment, fellow team members and
  others must all be brought together into an
  integrated whole. The integrated picture forms
  the control organising feature from which all
  decision making and action takes place.
• They key to coping in the information age is
  developing systems that support this process.
  Presenting a ton of data will do no good unless
  the data are transmitted, absorbed, and
  assimilated successfully and in a timely fashion
  by the human in order to form SA
• Salvendy, 2000

More data ? more information
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SA INTRODUCTION
More data ? more information
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SA INTRODUCTION

• Loss of SA is the leading causal factor in
• Military aviation mishaps (Hartel et al., 1991)
• Nuclear power operation (Hogg et al., 1993)
• Accidents among major air carriers, 88 of those
  involving human error could be attributed to
  problems with SA (Endsley, 1995)
• ATC errors (Rodgers et al., 2000)

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SA DEFINITION

• The perception of the relevant information in the
  environment, the comprehension of their meaning
  and the projection of their status in the near
  future
• Endsley, 1995

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SA FORMING PROCESS

• Process of forming SA has three levels
• Level 1 Perception of the Elements in the
  Environment
• First it is necessary to perceive critical
  factors in the environment
• Level 2 Comprehension of the Current Situation
• Understanding what the perceived factors mean,
  particularly with relevance to the goal
• Novices this maybe taxing to mental resources
  resulting in high MWL
• Level 3 Projection of the Future Status
• An understanding of what will happen with the
  system/product situation in the near future
• Experts spend more time anticipating possible
  future situations giving them the knowledge and
  time necessary to decide on the most favourable
  course of action
• (Endsley, 1995)

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DESIGN TO SUPPORT SA

• Present clear and unambiguous critical
  information required for making well-informed
  decisions in a coherent manner
• Avoid presenting irrelevant information (this
  will only increase noise and information
  overload)
• Exploit the way we organise information (grouping
  and hierarchical) wherever possible
• Information presented should also include the
  future state wherever possible
• For novel situations and novices, care should be
  taken to not exceed the WM capacity for realistic
  situations (2 3 steps or items)

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SA EXAMPLE
Good support for SA coherent presentation with
critical information
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SA GOOD OR BAD
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SA GOOD OR BAD
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SA GOOD OR BAD
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SA GOOD OR BAD
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SA GOOD OR BAD
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SA GOOD OR BAD
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SA GOOD OR BAD
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SA GOOD OR BAD
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SA GOOD OR BAD
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SA GOOD OR BAD
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SA GOOD OR BAD
Hong Kong MTR in-cab route map
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SA GOOD OR BAD

• The Intelligence signs on Thai roads providing
  information on the current situation for the
  related roads and junctions

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SITUATION AWARENSS

• How do we know which piece of information is
  relevant to SA and good decision making?
• SA requirement analysis methods
• Written material and document review
• Expert consultation
• User observation, verbal protocol, interviews

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SA COMPLEX SYSTEMS
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LOSS OF SA

• How do we lose situation awareness?
• The critical information necessary to make a well
  informed decision is not available
• An incorrect mental model is activated due to
  inappropriate, absence or ambiguous cues,
  resulting in RB and KB mistakes
• Lack of expertise or domain-specific knowledge
  necessary to understand the situation (absence of
  correct mental model)

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LOSS OF SA

• What happen if we lose SA?
• High utilisation of KB performance
• Heavy demand on mental resources
• High or unacceptable MWL
• Significant increase in RB and KB mistakes
• Reduced ability to detect and correct errors
• Accidents and disasters

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LOSS OF SA

• Factors contributing to loss of SA
• Endsley identified 8 SA demons
• Factors that work to undermine SA and may cause
  loss of SA

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SA EIGHT DEMONS

• Attentional Tunneling
• Focused on particular aspects or features of the
  environment to be processed to the detriments of
  the perception of other aspects which are also
  relevant to the goal
• Failure to divide attention particularly between
  within-modality stimuli
• One of the most significant challenges to SA
• Example Driver is concentrated on changing lanes
  and do not see the motorbike on the left hand side

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SA EIGHT DEMONS

• 2. Requisite Memory Trap
• The limited capacity and duration of memory
  retention in the WM pose a limit on information
  processing and development of integrated
  information
• Cannot take in all critical information and
  comprehend the situation poor or loss of SA and
  high MWL
• System designs that necessitate that people
  remember information, even short term, increase
  the likelihood of SA error
• Example Retaining route information in the
  memory and mapping it to the real-world picture

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SA EIGHT DEMONS

• 3. Workload, Anxiety, Fatigue and other Stressors
• Stressors time pressure, anxiety, uncertainty,
  noise, vibration, excessive heat/cold, poor
  lighting, physical fatigue, personal factors,
  alarms and alerts
• Reduce information gathering capability (become
  more disorganised) and WM capacity (pay less
  attention)
• Increase the tendency for attentional tunneling
• Often lead to premature closer (making a decision
  without taking into account all available
  information)
• Example Three Mile Island disaster

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SA EIGHT DEMONS

• 4. Data Overload
• Complex and rapidly changing environment
  constant input-processing-output
• Limited capacity of WM (serial processing,
  capacity, modality interference etc)
• At an unacceptable speed with unacceptable number
  of items of information data overload loss of
  SA and high MWL
• Coherent and effective presentation of data
  reduce risk of data overload
• Example Finding one particular piece of
  information in a 50-page document.
  Well-structured documents vs. a 50-page long
  text. Three Mile Island disaster

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SA EIGHT DEMONS

• 5. Misplaced Salience
• Salience catch attention
• Good draw attention to critical or highly
  important information
• Bad overuse or misuse can lead be misleading,
  distractive and/or overwhelming
• Interrupt SA formation process and increase MWL
• Examples Alerts and alarms in complex systems.
  The constant lit yellow light at some level
  crossings

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SA EIGHT DEMONS

• 6. Complexity Creep
• Systems/products may become more and more complex
  overtime
• The more features, the more complex, the more
  branching of the rules, the less able a person is
  to comprehend and form an internal representation
  of how the system works to make predictions of
  its behaviour
• Increase risk of incorrect interpretation of
  information presented and prediction of what is
  likely to happen
• Example high-end cameras, camcorders, video and
  CD recorders, stereos, microwaves and computer
  software such as Microsoft Office

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SA EIGHT DEMONS

• 7. Errant Mental Models
• Mental models are important mechanisms for
  building and maintaining SA
• Use of incorrect or incomplete mental models
• Poor comprehension and projection
• Difficult to realise and break out of
• Mode error thinking the system is in one mode
  when it is actually in another is the most
  dangerous and problematic of this demon
• Example The Midlands flight 092 crash near M1

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SA EIGHT DEMONS

• 8. Out-of-the-Loop Syndrome
• Automation lowers SA by putting people out of the
  loop
• People become less involved and less alert
• But humans are still decision maker and problem
  solver when things go wrong
• Complacency and overtrust less likely to
  monitor the job the automated system is doing
  loss SA of the evolving state of the system
  less able to deal with the problem appropriately
• Example The return of control to pilot when the
  autopilot suddenly and unexpectedly fail. Various
  complex systems

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SA MWL SUMMARY

• MWL refers to the interaction between task
  requirements and human capabilities or resources.
  The higher the MWL, the more demanding the tasks
  and the less available the resources to perform
  another task
• SA is the awareness and understanding of the
  current situation and ability to formulate future
  states
• The development and maintenance of SA compete for
  the same resources as other information
  processing tasks
• Expertise and skill reduces the competition for
  resources
• Mental models are important mechanisms for
  building and maintaining SA
• Provide critical information necessary to make a
  well-inform decision in a coherent manner for the
  user to comprehend and project the near future

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Any Questions?
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BREAK

• 15 MINUTES

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CASE STUDY THREE MILE ISLAND

• Summary of the incident at TMI
• A partial meltdown of the reactor core at the
  Three Mile Island nuclear power plant in
  Pennsylvania on 28rd March 1979 due to water
  leakage in the cooling system as a result of a
  routine maintenance
• The reactor shut down within 13 seconds
• Sixteen hours later, the emergency was finally
  brought under control.
• A small amount of radioactive material was
  release into the atmosphere
• No direct loss of life, but a billion dollar of
  damage and public mistrust
• The Nuclear Regulatory Commission has not
  reviewed an application to build a new nuclear
  power plant in the United States since
• Permanent closure of TMI2

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CASE STUDY THREE MILE ISLAND

• Loss of SA due to
• Lack of indication of malfunctioning (leakage as
  a result of maintenance),
• Bad mechanical design of the PORV displays,
• Delayed print out of the system state from the
  computer monitoring the system,
• Rapidly changing states of a complex system where
  activities are highly automated
• Automation resulting in human being designed
  out-of-the-loop
• Leads to RB and KB mistakes
• Delay in detection and recovery