referensi the load of mental work final

Department of Psychology s Institute for Simulation and TrainingUniversity of Central FloridaOrlando, FL 32826Measuring the Load of Mental Work

Methods and TechniquesP.A. HancockPresentation for the Class of 2008

Human Factors II EXP 6257

January 24th, 2008

Measuring the Load of Mental Work

Structure of the Lecture:

i) What is Mental Workload?

ii)Why Measure Mental Workload?

iii) Methods to Measure Mental Work.

iv)Current Applications and Future Directions.

Hancock, P.A., & Meshkati, N. (1988). (Eds.). Human mental workload. North-Holland: AmsterdamAvailable at: www.mit.ucf.edu

What Is Mental Workload?Mental workload is the portion of operators limited mental capacities actually required to perform a particular task.

Mental reserves are the difference between capacity required and capacity available.

Mental effort is the voluntary matching of mental capacities with that needed for task success.

Increase in Mental Workload often precedes Performance Failure.

The Need To Measure Mental WorkloadComes From The Changing Nature of Work

But Still Work Overload

How Hard Are These People Working?Apparent UnderloadApparent Overload


There are FOUR Basic Methodologies:

i) Primary Task Performance.

ii) Subjective Response.

iii)Physiological Assessment (Central and Peripheral).

iv)Secondary Task Techniques.

Meshkati, N., Hancock, P.A., Rahimi, M., & Dawes, S.M. (1995). Techniques of mental workload assessment. In: J. Wilson and

E.N. Corlett, (Eds.). Evaluation of human work: A practical ergonomics methodology. London: Taylor & Francis.Available at: www.mit.ucf.edu


Hancock, P.A., & Meshkati, N. (1988). (Eds.). Human mental workload. North-Holland: AmsterdamAvailable at: www.mit.ucf.eduPrimary Task Performance

Primary Task TechniquesMeasures the Performance Outcome as a function of Primary Task Demand

How well are you Flying?How well are you Driving?Notice that its not so easy to specify well in complicated performance environments.

Primary Task Techniques

As task load increases, the additional demands on mental capacities result in a degradation in performance

Advantages of This Measure:

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

Disadvantage of This Measure:

Only sensitive to changes in workload at the limits of mental capacity

If operators can compensate for increased workload by increasing their Effort, the primary task measure is insensitive

Mental Workload not distinguished from performance outcome

Primary Task TechniquesWhat About Failure?

Most of the time wed like to know about Mental Workload to know how much is too much?

Primary Task measures do not tell us this.

So, - they fail to be informative just at the time they are needed most!

Multiple Task DemandsSecondary Task Performance

Secondary Task MeasuresPrimary Task Demand (PTD)Performance LevelDifficult (D)Easy (E)Maximum Capacity (Without Impaired Performance).Moderate (M)PPPS3S2S1PTDE M DS1S2S3


Hancock, P.A., & Caird, J.K. (1993). Experimental evaluation of a model of mental workload.

Human Factors, 35, 413-429. Available at: www.mit.ucf.eduSubjective Measures

Subjective Responses

If You Want to Know How Hard Someone is Working Ask Them:

You Can Formally Ask Them Through Standard Techniques.

Two of the Most Popular are SWAT and NASA-TLX.

The Advantage: It is Easy to Do and Has high Face Validity

The Disadvantage: Often Performance and Perception Deviate

Subjective Workload Assessment Technique (SWAT).

Developed by the United States Air Force.

There are THREE Sources of Workload: Time, Effort, and Stress.

Each has THREE Levels 1=Low, 2=Medium, 3=High.

You begin by Putting the 27 Cards

(3 Sources X 3 Levels X 3 Combinations) into Order from 1-27.

Subjects rate each EVENT by giving a number for each,

(e.g., Time=2, Effort=1, Stress=3).

Looking up this Combination in the Card Sort Gives you

the Workload on a 0-100 Scale.

NASA-TLX (Task Load Index).

Developed by NASA (duh!).

There are SIX Sources of Workload:

Temporal Demand, Effort, Stress, Own Performance, Frustration, Physical Demand

Each is Compared Pairwise against the Others to give a Rank Order (0-5).

Subjects rate each EVENT by giving a 0-100 score for each Source.

These values are multiplied by the RANK and the totalis divided by 15 to get the Workload Score on a 0-100 Scale.

Measuring the Load of Mental WorkCentral vs. Peripheral NS Measures

Hancock, P.A., Meshkati, N., & Robertson, M.M. (1985). Physiological reflections of mental workload.

Aviation, Space, and Environmental Medicine, 56, 1110-1114. Available at: www.mit.ucf.eduPhysiological Measures

Eyeblink & Reflex ModificationElectroencephalography(EEG)Pupillometry/EyetrackingElectrocardiography(ECG)

Physiological Reflections of Mental Workload

Pupil DiameterKahneman & Beatty (1966; 1967); Hakerem & Sutton (1966); Hess & Polt (1964)

Chart8

0.12

0.225

0.214

0.31

0.55

Number of Digits

Pupil Diliation (mm)

Sheet1

30.12

40.225

50.214

60.31

70.55

Sheet1

Number of Digits


Chart5

0.067

0.077

0.05

0.13

0.16

0.2

0.23

0.18

0.13

0.095

0.065

Auditory Detection Difficulty


Sheet1

-300.067

-240.077

-180.05

-120.13

-60.16

00.2

60.23

120.18

180.13

240.095

300.065

Sheet1

0

0

0

0

0

0

0

0

0

0

0

Pitch Difference (Hz)


Chart3

0.03

0.04

0.05

0.14


Sheet1

No Task0.03

Blanks0.04

Misses0.05

Hits0.14

Sheet1

0

0

0

0


Chart1

22

18.5

12.2

11.1

Math Problem

% Pupil Diliation

Sheet1

16 x 2322

13 x 1418.5

8 x 1312.2

7 x 811.1

Sheet1

0

0

0

0

Problem

% Pupil Diliation

Visual Scanning and WorkloadUsed extensively in aviation researchTole, et al. (1982) Visual scanning behavior and mental workload in aircraft pilotsgaze characteristics on cockpit instruments varied as a function of the level of difficulty of a verbal loading taskmean dwell time of each fixation on the pilot's primary instrument increased as a function of task load scanning behavior was also a function of the estimated skill level of the pilots, with novices being affected by the loading task much more than experts. Authors argue that visual scanning of instruments in a controlled task may be an indicator of both workload and skill

Visual Scanning and Workload

Head Mounted Version

Desk Mounted Version

Time-Based ECG and WorkloadBonner & Wilson (2001)Monitored pilots throughout test and evaluation of an aircraftNote differences between subjective workload and HR

MeasureHRVHeart RatePupilDiameterEye TrackingEEGERPReliabilityValiditySensitivityDiagnosticityInvasivenessCostPost-ProcessingTemporal Sensitivity

Measurement Techniques: Advantages and Disadvantages

i) Primary Task Performance.(Data Easily Available, Future Failure Unpredictable).

ii) Secondary Task Technique.(Diagnostic, Administration is Intrusive)..

iii) Subjective Measures.(High Face Validity, Often Dissociate).

iv) Physiological Assessment.(Unobtrusive, Expensive Data [but getting cheaper]).

AviationPilot workloadMaritimeShip navigationGroundCar and bus drivers workloadAir traffic controlAutomation cueing modulates cerebral blood flow and vigilance in a simulated air traffic control taskShift-workPerformance dependent upon shift and workloadPeacekeepingDifferential workload of peacekeepersBusiness costs employee benefits managers are hoping that technology will help them cope with increasing workloadsEmployee burnoutTraining effectivenessHuman computer interactionHome-careNursingHospital readmissionsParentingConsumerismProfessor productivityto improve academic qualityStudent successTo name just a few...Current Applications and Future Directions

Variance in Shear ForcesAfter: Marras, W. (2005), Ohio State UniversityIf 20% of the Forces calculated in Physical Work are Personality Factors, what is that number for Cognitive Work.After: Marras, W. (2005), Ohio State University

Combined Physical and

Mental Workload

CURRENT APPLICATIONS

AND

FUTURE DIRECTIONS

Chart3

0.00122

0.02012

0.0000000754

0.00503

0.00238

0.00007117

0.00095147

0.02640937

0.07663

Anterior-Posterior

Weight15.1%

Pacing1.8%

Soc Env0.1%

Gender0.7%

Serial0.0%

Asymmetry0.9%

Anthro57.7%

Personality19.9%

Simult3.8%

discussion graphs

Trunk PostureTrunk VelocityHip PostureHip VelocityExtensor Muscle ActivityFlexor Muscle ActivityTrunk KinematicsLateral ShearA-P ShearCompression

Asymmetry0.01130.0020.0070.0020.01270.0430.0000.0130.00120.002

Weight0.01160.0030.0080.0070.05710.0430.0550.0310.02010.170

Serial0.00020.0010.0000.0070.00040.0000.0000.0000.00000.001

Simultaneous0.01020.0010.0440.0050.00960.0130.0110.0390.00500.055

Pacing0.00080.0070.0000.0100.00640.0030.0040.0010.00240.020

Soc Env0.00020.0000.0000.0010.00020.0000.0000.0000.00010.000

Gender0.04880.0480.0360.0360.13210.1310.0760.0170.00100.032

Personality0.01890.0180.0260.0310.04540.0190.0400.0120.02640.018

Anthropometry0.06290.0690.1160.0610.06510.0540.0530.0160.07660.010

0.3487REO0.2868LIO0.2570RIO0.2053

-0.018.Intercept-0.28.Intercept0.23.Intercept-0.909.

-0.0950.1497ASYM0.060.1354ASYM0.020.0019ASYM0.030.0167Asymmetry

0.0110.0361WGHT0.0070.0425WGHT0.0180.0643WGHT0.0120.0556Weight

0.0060.0002CONC-0.0080.0000CONC0.00040.0006CONC0.020.0012Ment Conc

0.0560.0209CNTR0.010.0225CNTR0.070.0059CNTR0.020.0062Control

0.0170.0021FREQ0.010.0015FREQ0.030.0107FREQ0.060.0094Lift Freq

-0.0080.0005STRS-0.0020.0001STRS-0.010.0004STRS-0.0080.0003Soc Env

0.0120.0558GNDR0.080.0438GNDR0.150.0236GNDR0.100.0128Gender

0.0710.02690.043EI-0.010.00090.004EI0.080.01690.061EI0.030.00600.018Personality

0.0150.0043NS0.0060.0000NS-0.070.0199NS-0.030.0105Anthropometry

0.0040.0002JP0.020.0026JP0.050.0039JP0.010.0011

-0.0520.0114TF0.0050.0001TF-0.050.0199TF0.010.0004

-0.0050.00450.019GW-0.0050.00470.017CF0.020.00050.008GW-0.010.00280.009

-0.0400.0027AC0.010.0005GW-0.010.0026ACR0.030.0011

0.0700.0084ACR0.020.0012ACR-0.030.0010AF-0.020.0006

-0.0030.0020AG-0.050.0055AF0.030.0006AG-0.050.0031

0.0020.0005AW0.0030.0025AG0.040.0016AW0.000.0009

-0.0270.0013CRW0.0020.0010AW-0.0030.0008

CRG-0.030.0014CRG-0.030.0006

-0.0010.0006STHT0.0020.0004STHT-0.0020.0067STHT0.0050.0003

-0.0010.0025BWT-0.0020.0080BWT-0.0010.0035BWT-0.0040.0023

0.0230.0168TC0.010.0123TC0.020.0023TC0.0390.0077

-0.0050.0015TDICTDIC0.030.0504TDIC0.0090.0639

TBICTBIC-0.010.0183TBIC-0.0030.0023

0.0210.0210.0810.077

discussion graphs

0

0

0

0

0

0

0

0

Sagittal Trunk Position

Simult_wght

0

0

0

0

0

0

0

0

0


0

0

0

0

0

0

0

0


0

0

0

0

0

0

0

0

0

Trunk Posture

Simultaneous6.2%

Personality11.5%

Anthropometry38.1%

Asymmetry6.8%

Serial0.1%

Gender29.6%

Soc Env0.1%

Pacing0.5%

Weight7.0%

0

0

0

0

0

0

0

0

0

Hip Posture

Simultaneous18.5%

Personality10.7%

Anthropometry48.9%

Asymmetry3.0%

Serial0.2%

Gender15.3%

Soc Env0.1%

Pacing0.2%

Weight3.2%

0

0

0

0

0

0

0

0

0

Trunk Velocity

Weight2.2%

Pacing4.5%

Soc Env0.2%

Gender32.3%

Serial0.5%

Asymmetry1.0%

Anthropometry46.3%

Personality12.2%

Simultaneous0.8%

0.002

0.007465

0.007318195

0.00479

0.00981

0.000528095

0.0363

0.030835285

0.061017385

Hip Velocity

Weight4.7%

Pacing6.1%

Soc Env0.3%

Gender22.7%

Serial4.6%

Asymmetry1.2%

Anthropometry38.1%

Personality19.3%

Simultaneous3.0%

0.0127487617

0.05714

0.000391277

0.009595

0.0064133333

0.0001963217

0.1320883333

0.0453890133

0.0650540683

Extensor Muscle Activity

Simultaneous2.9%

Personality13.8%

Anthropometry19.8%

Asymmetry3.9%

Serial0.1%

Gender40.1%

Soc Env0.1%

Pacing1.9%

Weight17.4%

0

0

0

0

0

0

0

0

0

Flexor Muscle Activity

Weight13.9%

Pacing0.9%

Soc Env0.0%

Gender42.8%

Serial0.0%

Asymmetry14.1%

Anthropometry17.6%

Personality6.4%

Simultaneous4.2%

0

0

0

0

0

0

0

0

0

Trunk Moments

Simultaneous4.5%

Personality16.7%

Anthropometry22.2%

Asymmetry0.2%

Serial0.1%

Gender31.8%

Soc Env0.0%

Pacing1.7%

Weight22.9%

0

0

0

0

0

0

0

0

0

Lateral Shear Force

Weight24.1%

Pacing0.4%

Soc Env0.0%

Gender13.4%

Serial0.1%

Asymmetry9.9%

Anthropometry12.3%

Personality9.1%

Simultaneous30.7%

0

0

0

0

0

0

0

0

0

Anterior-Posterior Shear Force

Simultaneous3.8%

Personality19.9%

Anthropometry57.7%

Asymmetry0.9%

Serial0.0%

Gender0.7%

Soc Env0.1%

Pacing1.8%

Weight15.1%

0

0

0

0

0

0

0

0

0

Compression Force

Control18.0%

Personality5.9%

Anthropometry3.3%

Asymmetry0.5%

Ment Conc0.2%

Gender10.3%

Soc Env0.0%

Lift Freq6.4%

Weight55.4%

6.8WGHT=1511.4WGHT=256.811.4WGHT=25

MFX249.234.7227779335355.746.7082272406373.998.4534065725552.1813.6300277926

MFY543.434.6514334006703.37.0803695299593.915.517694116812.848.8817039135

MFZ3574.1522.61506620694611.1627.5972160394092.1426.55788729545470.7139.0155633121

00

00

General Placement

Controlled Placement

00

00

General Placement


00

00

General Placement


00

00

General Placement


00

00

General Placement


00

00

General Placement


00

00

General Placement


00

00

General Placement


00

00

General Placement


00

00

Simple Simultaneous Processing

Complex Simultaneous Processing

Box Weight (kg)

Lateral Shear Force (N)

00

00



Box Weight (kg)

A-P Shear Force (N)

0026.557887295422.615066206922.615066206926.5578872954

0039.015563312127.59721603927.59721603939.0155633121



Box Weight (kg)

Compression Force (N)

NeuroergonomicsNeuroergonomics involves the examination of the neural bases of perceptual, cognitive and motorfunctions in relation to real-world applications as mediated through Machines.Hancock, P.A. (1997). On the future of work. Ergonomics in Design, 5 (4), 25-29.Adaptive Human-MachineSystems

1 ms10 ms2 s2 minPETfMRITCDS5 mm1 cm10 cm20 cmSPATIAL RESOLUTIONTEMPORAL RESOLUTIONEEG,ERPsRESOLUTION SPACE OF BRAIN IMAGING TECHNIQUES FOR ERGONOMIC APPLICATIONS0.1 mmMore invasive, Less practicalLess invasive, More practicalMEGNIRS

Vigilance is a Long-Standing Problem.Sources of Performance Influence Include: Event Rate Signal Salience Stress/Workload/Fatigue Glare, Noise, Temperature, Vibration, TOD, Drug Effects etc Memory Load Successive vs. Simultaneous Comparisons

Feedback

Hit vs. Miss vs. FA KR/KP

Individual Differences

Introversion/Extraversion, Age, Sex, Expertise

Warm, J.S. (Ed.). (1984). Sustained attention in human performance. New York: Wiley.Workload and Vigilance

P.A. Hancock, D.Sc., Ph.D.

Department of Psychology, and

The Institute for Simulation and Training

University of Central Florida

Orlando, FL 32826

[email protected]

Personal BiographyOrlando, Florida, January, 2007. Human Factors IIPeter A. Hancock Professor of Psychology and Institute for Simulation and Training, University of Central FloridaPeter Hancock is Provost Distinguished Research Professor in the Department of Psychology, the Institute for Simulation and Training, and at the Department of Civil and Environmental Engineering at the University of Central Florida. He also holds courtesy appointments at Minnesota, Michigan, and MIT. He is the author of over five hundred refereed scientific articles and publications including: Human Performance and Ergonomics; Stress, Workload, and Fatigue; and Essays on the Future of Human-Machine Systems. He has been continuously funded by extramural sources for every year of his professional career, including support from NASA, NIH, NIA, FAA, FHWA, the US Navy, the US Army and the US Air Force. In 2000 he was awarded the Sir Frederic Bartlett Medal of the Ergonomics Society of Great Britain for lifetime achievement. He was the Keynote Speaker for the 2000 Meeting of the International Ergonomics Association. In 2001 he won the Franklin V. Taylor Award of the American Psychological Association and in association with his colleagues Raja Parasuraman and Anthony Masalonis, he was the winner of the Jerome Hirsch Ely Award of the Human Factors and Ergonomics Society for 2001. In 2002, he was awarded the Jastrzebowski Medal of the Polish Ergonomics Society for contributions to world ergonomics and in the same year was named a Fellow of the Ergonomics Society of Great Britain. He has been elected to a second, three-year term as a Member of the National Research Councils Committee on Human Factors. In 2003 he won the Liberty Mutual Medal of the International Ergonomics Association. His current experimental work concerns the evaluation of time an behavioral responses to high-stress conditions. His theoretical works concerns human relations with technology and the possible futures of this symbiosis. He is a Fellow of and past President of the Human Factors and Ergonomics Society.

Further Information can be garnered at: www.mit.ucf.edu

The Load of Mental Work

Workload-Performance DissociationsTask Demand (difficulty)Supply of ResourcesUnderloadOverloadMeasure ofPerformanceMeasure ofSubjectiveWorkload

With the Transition from Physical to Mental WorkComes the Need to Measure WorkloadAll Citations Available At: www.mit.ucf.edu

Workload: AppliedThe superiority of Adaptive AutomationThe allocation of a task or a function between the operator and the system [which] is flexible and responsive to operators performance and level of workloadImprove situational awareness, regulate workload, improve vigilance in high-risk environments, and help to maintain manual control skills. (Mouloua, Deaton, & Hitt in Hancock & Desmond, 2001; Parasuramanm, Bahri, Deaton, Morrison, & Barnes, 1992) Adaptive Automation Adaptive automation (AA) for managing operator workload through dynamic control allocations between the human and machine over time Low-levels of automation - superior performance Intermediate levels of automation - higher SA Not associated with Improved performance Reduced workload. (Kaber & Endsley, 2004)

Technology is a way of organizing the universe so that man doesn't have to experience it. -- Max FrischAviation - Automation & Workload in Aviation Systems

Information Overload/Complexity

Physical/Social Environment

Uncertainty

Human Performance under Stress

EEG

***The first definition is from ODonnell and Eggemeier (1986), the second from Gopher and Donchin (1986)***The first definition is from ODonnell and Eggemeier (1986), the second from Gopher and Donchin (1986)*******Adapted from ODonnell & Eggemeier, 1986, after I.D. Brown, 1964*************The study of workload (i.e., analyses of operators mental capacity as compared to their work demands) and its effects has been applied to a variety of applied settings such as, [see slide]

Air traffic control[see slide]. Measurement of the activation of this system, as a reflection of operator mental workload, can, therefore, inform the design of optimal automation cueing. By Hitchcock, Warm, Matthews, Dember, Shear, Tripp, Mayleben, Parasuraman,Theoretical Issues in Ergonomics Science; Jan2003, Vol. 4 Issue 1/2, p89, 24pShift-work, remember our speaker from a couple of weeks ago, who spoke about the depedence of performance upon the workload by shift-time (i.e., on a 12 hour shift, the higher workload should be at the beginning of the shift the reduce as the shift goes on because performance will drop off after the first 4 hours) [see slide]PeacekeepingThe peacekeeper: How the role of the modern soldier has changed and how that affects workloadDifferential workload of peacekeepers a world view deterioration of morale when trained to be soldiers but placed in watch-keeping/peacekeeping positions. An incidence when workload must match training.Koltko-Rivera, Ganey, Murphy, Hancock, & Dalton, HPSAA, 2004.Workload theory has also been applied to analyzeBusiness costsReports that U.S. employee benefits managers are hoping that technology and approaches to buy benefits will help them cope with increasing workloads based on a survey by John Hancock Life Insurance Co. Percentage of managers who want to increase efficiency by introducing the use of employee self-service technology [see slide]Survey Shows Many Benefits Managers Feel Swamped.National Underwriter / Life & Health Financial Services; 3/11/2002, Vol. 106 Issue 11, p21, 1/4p

Employee burnout higher workload, higher burnout

Training effectiveness higher workload, lower training effectiveness

HCI we will speak in more detail on that later in the presentation

Home-care higher workload, worse home-care

Nursing higher workload, less nursing care

Hospital readmissions higher workload, more likely to be readmitted to the hospitalParenting higher workload less parenting (less time spent with children and spouse and the time spent with them is of lower quality)

Professor ProductivityThis case study specifically focuses on how information regarding faculty workload, salary, and benefits can be used to improve academic quality. The International Journal of Educational Management 17, no. 5 (2003): 200-210

Student success higher workload, detrimental effects on success and quality of work (higher illness, higher drop-out rate, etc)

*********Yeh & Wickens (1988); Hancock (1996)**Aviation Workload has been a focus of human factors research since, probably, before the term workload was coined. Did the pilot have too many controls to consider (split-attention), or too much input form his/her environment (cognitive overload), or was there too much monitoring (vigilance decrement), or was there a combination of things that increased the pilots stress/workload that resulted in performance decrement and possibly much worse consequences.

Our book has a wonderful chapter on [see slide]

[CLICK]Adaptive AutomationThere have been several studies on adaptive automation as they related to workload in a multitude of applied areas (e.g., driving, HCI). One study,The effects of level of automation and adaptive automation on human performance, situation awareness and workload in a dynamic control task.Kaber & Endsley, 2004. Theoretical Issues in Ergonomics Science; Mar/Apr, Vol. 5 Issue 2, p113, 41pLooked at [see slide](among other things) The experiment was conducted to assess the performance, SA and workload effects of low, intermediate and high levels of automation, compared to completely manual control and fully automated control of a dynamic control task. Results revealed Low-level automation produced superior performance and intermediate levels of automation facilitated higher SA, but this was not associated with improved performance or reduced workload.**

referensi the load of mental work final

Documents