NASA-STD-3001 Technical Brief

Relevant Technical 

Requirements

Cognitive Workload 

Assessment Methods

OCHMO-TB-032

Rev C 

NASA-STD-3001 Volume 1, Rev C

[V1 3003] In-Mission Preventive Health Care

[V1 4011] Mission Cognitive Status

[V1 4014] In-Mission Completion of Critical 

Tasks 

[V1 5002] Crewmember Training

NASA-STD-3001 Volume 2, Rev D

[V2 3006] Human-Centered Task Analysis 

[V2 3101] Iterative Developmental Testing

[V2 10001] Usability 

[V2 10002] Design-Induced Error

[V2 10003] Operability

[V2 10004] Controllability and 

Maneuverability During Manual Control 

(Handling Qualities – Level 1)

[V2 5052] Controllability and 

Maneuverability During Manual Control 

with Deficiencies (Handling Qualities –

Level 2)

[V2 5006] Situation Awareness

[V2 5007] Cognitive Workload

[V2 10200] Physical Workload

[V2 10161] Automation System Status 

Provision

Executive Summary

Cognitive Workload is the user’s perceived level of 

mental effort that is influenced by many factors, 

particularly task load and task design.

The workload measurement enables standardized 

assessment of whether temporal, spatial, cognitive, 

perceptual, and physical aspects of tasks and the crew 

interfaces for these tasks are designed and 

implemented to support each other. Application of 

workload measurement for crew interface and task 

designs in conjunction with other performance 

measures, such as usability and design-induced error 

rates, helps assure safe, successful, and efficient 

system operations by the crew. 

Designers need to consider the workload of the user 

when designing and producing an interface or 

designing a task. Low workload levels are associated 

with boredom and decreased attention to task, 

whereas high workload levels are associated with 

increased error rates and the narrowing of attention 

to the possible detriment of other information or 

tasks (Sandor et al., 2013). Humans perform best 

when they are neither bored nor overburdened, and 

when periods of work and rest are equitably mixed 

together.

Workload assessments should be integrated early and 

often through the engineering design life cycle so that 

related design decisions can be made from a datadriven perspective and ensure crew safety and 

performance.
NASA-STD-3001 Technical Brief

OCHMO-TB-032 Cognitive Workload Assessment Methods

NASA Office of the Chief Health & Medical Officer (OCHMO)

This Technical Brief is derived from NASA-STD-3001 and is for reference only.

It does not supersede or waive existing Agency, Program, or Contract requirements.

Background

11/13/2023

Rev C 2

• Previous studies have revealed the deleterious effects of workload that is either too high or too 

low (Measuring and Evaluating Workload: A Primer, NASA/TM—2010-216395).

• High workload leads to humans hurrying performance, committing more errors, yielding 

poor accuracy, becoming frustrated, uncomfortable, and fatigued, and having poor 

awareness of their surroundings.

• Low workload has been linked to high error rates, frustration, fatigue, and poor awareness 

of surroundings as they become bored, as their attention drifts, and as complacency sets in.

• Anecdotal reports from astronauts (Scheuring et al., 2007) indicate that at times of high intensity, 

workload can result in mental and physical fatigue. 

• Skylab 4: Crewmembers reported that they quickly ran into difficulty due to work overload. The 

fast-paced schedule and workload of the mission initially caused crewmembers to consistently 

“feel” behind on tasks as well as demoralized. Mission Control personnel later acknowledged that 

the schedule had been such that it had not given the crewmembers adequate time in which to 

adjust to their environment (Uri, J. 2020). 

• Apollo: Some of the Apollo crews reported serious mental fatigue while they were performing 

lunar surface extravehicular activities (Scheuring et al., 2007). 

• ISS: Astronauts experienced high tempo operations and high workloads (Behavioral Issues 

Associated with Long Duration Space Expeditions: Review and Analysis of Astronaut Journals 

Experiment 01-E104 (Journals): Final Report , 2010):

• “The fatigue was evident when a couple of minor mistakes were made today on some 

payload activities. The ground caught the mistake and helped me out. But it is an obvious 

indicator of fatigue. I feel that the workload is going up; these last few weeks seem to have 

been pretty taxing. I’m very tired.”

• Titan 11 missile accident, 1980, Damascus, Arkansas: 

Missile exploded, ejecting 9-megaton nuclear warhead. 

A series of human factors issues were reported in this 

incident. Crew had been working for 12 hours prior to the 

incident.
NASA-STD-3001 Technical Brief

OCHMO-TB-032 Cognitive Workload Assessment Methods

NASA Office of the Chief Health & Medical Officer (OCHMO)

This Technical Brief is derived from NASA-STD-3001 and is for reference only.

It does not supersede or waive existing Agency, Program, or Contract requirements.

Background

11/13/2023

Rev C 3

• Workload is closely linked to other human factors concepts such as usability, physical workload, 

anthropometrics, error rates, and handling qualities. 

• Significant usability or handling quality issues will often drive high workload ratings.

Iterative Detailed Operational 

Task & Error Analysis

Ensure 

Usability

RightSized 

Workload

Minimize 

Errors

Ensure operational 

capability & timeliness 

NASA-STD-3001 Vol 2 

Rev D [V2 10001; 10003]

• Can the user complete 

the task in/at the time

required?

Right-Sized Workload 

NASA-STD-3001 Vol 2 

Rev D [V2 5007; 10200]

• Can the user 

cognitively process all 

information sources 

and physically execute 

all action within/at the 

time required?

Design-Induced Error 

NASA-STD-3001 Vol 2 Rev 

D [V2 10002]

• Do intentional user 

actions result in 

unintended outcomes?

• Are catastrophic errors 

eliminated by design?

Human-in-the-Loop (HITL) 

Iterative Testing

Relevant Technical Requirements 

[V2 5007] Cognitive Workload, [V2 10001] Usability, [V2 10002] Design-Induced Error, [V2 10003]

Operability, [V2 10200] Physical Workload

From: NASA-STD-3001 Volume 2, Rev D

Reference NASA OCHMO-TB-005 Usability, Workload, & Error
NASA-STD-3001 Technical Brief

OCHMO-TB-032 Cognitive Workload Assessment Methods

NASA Office of the Chief Health & Medical Officer (OCHMO)

This Technical Brief is derived from NASA-STD-3001 and is for reference only.

It does not supersede or waive existing Agency, Program, or Contract requirements.

Background

11/13/2023

Rev C 4

Cognitive Workload can be suboptimal either because it is:

• Low due to low arousal: Technological advances (e.g., automation) introduced to improve system 

performance (and reduce workload) may sometimes create underload where the operator simply 

monitors the automation and removes them from the active control loop (Parasuraman & Riley, 1997); 

or may shift operator workload from one focus to another without achieving the expected reduction in 

workload. When an operator experiences excessively low task demands they may experience a state of 

mental underload. 

• High due to excessive task demands: When operators are faced with excessive task demands and their 

attentional resources are exceeded, they become overloaded. Mental overload occurs when the 

demands of the task are so great that they are beyond the attentional capacity of the operator. 

Overload and underload can be detrimental to task performance. Operators may become less likely to 

attend to potentially important sources of information and fail at the task.

Workload Assessments

Workload assessment tools such as the Bedford Scale or NASA Task Load Index (TLX) are available to help 

answer the following question: “Can the user cognitively process all information sources and execute 

all actions within/at the time required?”

• NASA has determined that for space flight programs, workload should be assessed using the Bedford 

scale. Other types of scales (e.g., NASA Task Load Index (TLX)) are diagnostic or multi-dimensional, 

meaning that they allow the source of the workload to be localized. These types of scales are 

advantageous to use during the design phase, where modifications based on workload evaluations are 

possible. However, during the verification phase, the Bedford scale is the most appropriate.

• Metrics of Cognitive Workload measure the mental demands required of a person to perform a given 

task. Appropriate workload levels keep the crewmember engaged in the task, while allowing spare 

mental capacity to deal with concurrent tasks or issues.

• Some of the most safety-critical decisions and actions associated with operating a spacecraft are 

carried out in situations where the crew is multi-tasking, processing numerous inputs, and making 

decisions concerning multiple, possibly unrelated, problems. Work may also demand abrupt shifts 

between tasks performed alone and tasks relying on others’ inputs.

Low Cognitive Workload High

Performance

Good

Bad

Acceptable Level
NASA-STD-3001 Technical Brief

OCHMO-TB-032 Cognitive Workload Assessment Methods

NASA Office of the Chief Health & Medical Officer (OCHMO)

This Technical Brief is derived from NASA-STD-3001 and is for reference only.

It does not supersede or waive existing Agency, Program, or Contract requirements.

The Bedford Scale

The Bedford scale is a uni-dimensional rating scale designed to identify operator's spare mental capacity 

while completing a task. The single dimension is assessed using a hierarchical decision tree that guides the 

operator through a ten-point rating scale, each point of which is accompanied by a descriptor of the 

associated level of workload.

1. The operator rates their workload on a uni-dimensional scale from 1 to 10. 

2. The operator is asked on a three-rank ordinal structure whether 1) it was possible to complete the 

task, (2) the workload was tolerable, or (3) the workload was satisfactory without reduction. Then, the 

operator ranks their workload on the respective rating scale end points (1-10) from workload 

insignificant to task abandoned.

3. This measures whether it was possible to complete the task, if workload was tolerable for the task, 

and if workload was satisfactory without reduction (Miller, 2001). 

Reference Data

11/13/2023

Rev C 5

NASA-STD-3001, Volume 2 Rev D sets limits for Cognitive Workload using the Bedford scale:

[V2 5007] Cognitive Workload The system shall provide crew interfaces that result in Bedford 

Workload Scale ratings of 3 or less for nominal tasks and 6 or less for off-nominal tasks. 

• Workload measurements for nominal tasks (critical or frequent) are limited to a Bedford Workload 

Scale rating of 3 or less.

• Workload measurements for off-nominal tasks (non-critical or infrequent) are limited to a Bedford 

Workload Scale Rating of 6 or less.

• Workload levels may be modulated (raised or lowered) through the combination of user-interface 

design and task design (e.g., task simplification, subtask combination and sequencing, and the 

distribution of tasks among multiple crewmembers and between crew and automation).
NASA-STD-3001 Technical Brief

OCHMO-TB-032 Cognitive Workload Assessment Methods

NASA Office of the Chief Health & Medical Officer (OCHMO)

This Technical Brief is derived from NASA-STD-3001 and is for reference only.

It does not supersede or waive existing Agency, Program, or Contract requirements.

NASA Task Load Index (TLX)

The NASA TLX may be preferred for developmental testing, due to its diagnostic properties. Other 

validated indicators of workload may be used by programs with approval from the Health and Medical 

Technical Authority.

The NASA TLX is a multi-dimensional rating scale for operators to report their mental workload. It uses six 

dimensions of workload to provide diagnostic information about the nature and relative contribution of 

each dimension in influencing overall operator workload. Operators rate the contribution made by each of 

the six dimensions of workload to identify the intensity of the perceived workload. The NASA TLX provides 

an overall score based on a weighted average of the six subscale ratings as described in the figure below.

Reference Data

11/13/2023

Rev C 6

• The degree to which 

each of the six factors 

contributes to the 

workload of the 

specific task to be 

evaluated from the 

rater’s perspective is 

determined by their 

responses to pairwise comparisons 

among the six factors. 

• Magnitude ratings in 

each subscale are 

factors deemed most 

important in creating 

the workload of the 

task and are obtained 

after each 

performance of a task 

or task segment. 
NASA-STD-3001 Technical Brief

OCHMO-TB-032 Cognitive Workload Assessment Methods

NASA Office of the Chief Health & Medical Officer (OCHMO)

This Technical Brief is derived from NASA-STD-3001 and is for reference only.

It does not supersede or waive existing Agency, Program, or Contract requirements.

Application

• Cognitive Workload is an important component of crew interaction with systems. Designers must 

consider it when designing hardware and software with crew interfaces, procedures, and operations.

• At the earliest stages of the design life cycle, integration of crew workload should focus on defining the 

various tasks that are relevant to workload.

• Task analysis is the method for identifying which crew and systems tasks will be performed during each 

mission phase, the hardware associated with the task, and whether the task is expected to contribute 

to crew workload. Task analysis should continue to mature as the design progresses. After task 

definitions, the next stage is to start assessing crew workload in a series of simulated vehicle tasks.

• When designing a human-system interface to support a crew task, designers are to assess the 

operation as part of a human-in-the-loop (HITL) simulation to determine the workload associated with 

that operation. If the Cognitive Workload is judged to be so high that a human has little or no spare 

capacity to deal with a concurrent problem, the task and supporting interfaces are to be redesigned.

• System design can aid in the selection and organization of relevant information to reduce the level of 

cognitive effort required to attend to a stimulus in the environment.

• Information should be prioritized so that the most important or critical information is displayed at all 

times and less important or critical information can be displayed upon a user’s request (Federal 

Aviation Administration, 2011).

11/13/2023

Rev C 7

Phase A

Develop ConOps, 

allocate functions 

between user & 

system, and 

decompose 

functions in task & 

error analysis

Phase B

Involve users & 

SMEs in design 

concept 

evaluations; 

measure 

workload, 

usability, & error; 

iterate design

Phase C

Finalize design 

with findings from 

user evaluation

Phase D

Verify and 

validate 

integrated system 

design with user 

testing of 

usability, 

workload, & error 

Phase E

Operations and 

Sustainment

Phase F

Closeout

Cognitive Workload should be assessed through the engineering design life cycle

[V2 3006] Human-Centered Task Analysis Each human space flight program or project shall perform a 

human-centered task analysis to support systems and operations design. From: NASA-STD-3001 

Volume 2, Rev D
NASA-STD-3001 Technical Brief

OCHMO-TB-032 Cognitive Workload Assessment Methods

NASA Office of the Chief Health & Medical Officer (OCHMO)

This Technical Brief is derived from NASA-STD-3001 and is for reference only.

It does not supersede or waive existing Agency, Program, or Contract requirements.

Application

11/13/2023

Rev C 8

• When users are required to monitor multiple displays, important events should occur in all of the 

displays to promote effective monitoring performance (Warm et al., 2008).

• Coding techniques that have strong attention-getting qualities (for example, color and flashing) should 

be used sparingly and judiciously (Federal Aviation Administration, 2011).

• Workload assessments should be integrated early and often through the engineering design life cycle 

so that related design decisions can be made from a data-driven perspective and ensure crew safety 

and efficiency. It is easier and more cost-effective to correct deficiencies in hardware or procedures 

that produce high crew workload during the early design phases rather than just before vehicle 

certification.

• The Bedford Workload Scale has been selected by NASA as the workload verification method for a 

number of program workload requirements. However, the NASA TLX may be preferred for 

developmental testing, due to its diagnostic properties. Other validated indicators of workload may be 

used by programs with approval from the Health and Medical Technical Authority.

• When using the Bedford scale assessment to evaluate Cognitive Workload, some guidelines need to be 

followed:

 Participants must be briefed on what defines workload and should understand that they will be 

asked to rate their own workload. There are no “right” or “wrong” answers.

 Operator comments should be solicited as part of the testing. The comments should be as specific 

as possible to enable the engineers to make appropriate changes to the design.

 An appropriate number of operators should be tested to ensure meaningful results. 

 Testing should include worst case conditions (including off-nominal conditions) to simulate the 

stress the operator will be under while performing the operation.

 Testing should also consider the operators physiological condition during performance of the task. 

Physiological conditions that influence performance include, but are not limited to: core body 

temperature, humidity levels, hydration levels, strength, aerobic capacity, and orthostatic 

intolerance.
NASA-STD-3001 Technical Brief

OCHMO-TB-032 Cognitive Workload Assessment Methods

NASA Office of the Chief Health & Medical Officer (OCHMO)

This Technical Brief is derived from NASA-STD-3001 and is for reference only.

It does not supersede or waive existing Agency, Program, or Contract requirements.

Back-Up

11/13/2023

Rev C 9
NASA-STD-3001 Technical Brief

OCHMO-TB-032 Cognitive Workload Assessment Methods

NASA Office of the Chief Health & Medical Officer (OCHMO)

This Technical Brief is derived from NASA-STD-3001 and is for reference only.

It does not supersede or waive existing Agency, Program, or Contract requirements.

Rev B  Rev C

• Updated information to be consistent with NASA-STD-3001 

Volume 1 Rev C and Volume 2 Rev D.

Rev A  Rev B

• Added additional information and application notes on 

specific technical requirements.

Original Rev A

• Updated information to be consistent with NASA-STD-3001 

Volume 1 Rev B and Volume 2 Rev C.

Major Changes Between Revisions

11/13/2023

Rev C 10
NASA-STD-3001 Technical Brief

OCHMO-TB-032 Cognitive Workload Assessment Methods

NASA Office of the Chief Health & Medical Officer (OCHMO)

This Technical Brief is derived from NASA-STD-3001 and is for reference only.

It does not supersede or waive existing Agency, Program, or Contract requirements.

NASA-STD-3001 Volume 1 Revision C

[V1 3003] In-Mission Preventive Health Care All programs shall provide training, in-mission capabilities, 

and resources to monitor physiological and psychosocial well-being and enable delivery of in-mission 

preventive health care, based on epidemiological evidence-based probabilistic risk assessment (PRA),

individual crewmember needs, clinical practice guidelines, flight surgeon expertise, historical review, 

mission parameters, and vehicle derived limitations. These analyses consider the needs and limitations

of each specific vehicle and design reference mission (DRM) with particular attention to parameters such 

as mission duration, expected return time to Earth, mission route and destination, expected radiation

profile, concept of operations, and more. In-mission preventive care includes, but is not limited to: (see 

NASA-STD-3001 Volume 1 Rev C for full technical requirement).

[V1 4011] Mission Cognitive Status Pre-mission, in-mission, and post-mission crew behavioral health and 

crewmember cognitive state shall be within clinically accepted values as judged by behavioral health 

evaluation.

[V1 4014] Completion of Critical Tasks The planned number of hours for completion of critical tasks and 

events, workday, and planned sleep period shall have established limits to assure continued crew health 

and safety.

[V1 5002] Crewmember Training Beginning with the astronaut candidate year, general medical training, 

including, but not limited to, first aid, cardiopulmonary resuscitation (CPR), altitude physiological training, 

carbon dioxide exposure training, familiarization with medical issues, procedures of space flight, 

psychological training, and supervised physical conditioning training shall be provided to the astronaut 

corps.

NASA-STD-3001 Volume 2 Revision D

[V2 3006] Human-Centered Task Analysis Each human space flight program or project shall perform a 

human-centered task analysis to support systems and operations design. 

[V2 3101] Iterative Developmental Testing Each human space flight program or project shall perform 

iterative human-in-the-loop (HITL) testing throughout the design and development cycle.

[V2 10001] Usability The system shall provide crew interfaces that result in a NASA-modified System 

Usability Scale (NMSUS) score of 85 or higher.

[V2 10002] Design-Induced Error The system shall provide crew interfaces that result in the maximum 

observed error rates listed in Table 5.1-1—Maximum Observed Design-Induced Error Rates.

[V2 10003] Operability The system shall provide interfaces that enable tasks to be performed successfully 

within the appropriate time limit and degree of accuracy. 

[V2 10004] Controllability and Maneuverability During Manual Control (Handling Qualities – Level 1)

The spacecraft shall exhibit Level 1 handling qualities (Handling Qualities Rating (HQR) 1, 2 and 3), as 

defined by the Cooper-Harper Rating Scale, during manual control of the spacecraft's flight path and 

attitude when manual control is the primary control mode or automated control is nonoperational.

[V2 5052] Controllability and Maneuverability During Manual Control with Deficiencies (Handling 

Qualities – Level 2) The system shall exhibit Level 2 (HQR 4-6) or better handling qualities during manual 

control in all other scenarios not specified in [V2 10004] Handling Qualities – Level 1.

Referenced Technical Requirements

11/13/2023

Rev C 11

View the current versions of NASA-STD3001 Volume 1 & Volume 2 on the 

OCHMO Standards website
NASA-STD-3001 Technical Brief

OCHMO-TB-032 Cognitive Workload Assessment Methods

NASA Office of the Chief Health & Medical Officer (OCHMO)

This Technical Brief is derived from NASA-STD-3001 and is for reference only.

It does not supersede or waive existing Agency, Program, or Contract requirements.

NASA-STD-3001 Volume 2 Revision D

[V2 5006] Situation Awareness Systems shall provide the Situation Awareness (SA) necessary for efficient 

and effective task performance and provide the means to recover SA, if lost, for anticipated levels of 

crewmember capability and anticipated levels of task demands.

[V2 5007] Cognitive Workload The system shall provide crew interfaces that result in Bedford Workload 

Scale ratings of 3 or less for nominal tasks and 6 or less for off-nominal tasks. 

[V2 10200] Physical Workload The system shall provide crew interfaces that result in a Borg-CR10 rating 

of perceived exertion (RPE) of 4 (somewhat strong) or less.

[V2 10161] Automation System Status Provision The automated system shall provide the human operator 

with the following information:

a. system state (e.g., position, location, hazardous condition, running, paused, faulted, completed, 

overridden, stopped, readiness)

b. projection of future state, including failure or decrements in performance (e.g., battery power versus 

traverse distance and assessment of uncertainty in projection of future state) and mode (e.g., 

Full/Partial/Manual/Test)

c. system health

d. configuration information (e.g., setup/input parameters, initial conditions, and terminating conditions)

Referenced Technical Requirements

11/13/2023

Rev C 12

View the current versions of NASA-STD3001 Volume 1 & Volume 2 on the 

OCHMO Standards website
NASA-STD-3001 Technical Brief

OCHMO-TB-032 Cognitive Workload Assessment Methods

NASA Office of the Chief Health & Medical Officer (OCHMO)

This Technical Brief is derived from NASA-STD-3001 and is for reference only.

It does not supersede or waive existing Agency, Program, or Contract requirements.

Reference List

1. Basner M, Dinges DF, Mollicone DJ, Savelev I, Ecker AJ, et al. (2014) Psychological and Behavioral 

Changes during Confinement in a 520-Day Simulated Interplanetary Mission to Mars. PLOS ONE 9(3): 

e93298. https://doi.org/10.1371/journal.pone.0093298

2. Behavioral Issues Associated with Long Duration Space Expeditions: Review and Analysis of Astronaut 

Journals Experiment 01-E104 (Journals): Final Report. (2010). 

https://lsda.jsc.nasa.gov/lsda_data/dataset_inv_data/ILSRA_2001_104__1740256372_.pdf_Expeditio

n_8_ILSRA-2001-104_2011_31_010100.pdf

3. Fatigue Risk Management in Aviation Maintenance: Current Best Practices and Potential Future 

Countermeasures, Federal Aviation Administration, June 2011

4. Flight Test Assessments of Pilot Workload, System Usability, and Situation Awareness of TASAR,HFES 

International Annual Meeting, Human Factors Principal Investigator, NASA Langley Research Center, 

2016

5. Measuring and Evaluating Workload: A Primer. Stephen M. Casner, NASA Ames Research Center, 

Moffett Field: 

https://pdfs.semanticscholar.org/3156/ae866b00a2ec9495a5b8b3df5422196d179a.pdf?_ga=2.17246

0323.140449752.1579710142-474163027.1579710142

6. Risk of Performance Decrements and Adverse Health Outcomes Resulting from Sleep Loss, Circadian 

Desynchronization, and Work Overload Rev. 2,HSRB-CR-SA-01743, 2019

7. Sandor, A., Schuh, S.V., and Gore, B.F. (2013). Evidence Report: Risk of Adverse Cognitive or Behavioral 

Conditions and Psychiatric Disorders. Human Research Program, National Aeronautics and Space 

Administration Lyndon B. Johnson Space Center Houston, Texas. 

https://humanresearchroadmap.nasa.gov/Evidence/reports/TASK.pdf

8. Psychological and Behavioral Changes during Confinement in a 520-Day Simulated Interplanetary 

Mission to Mars, March 2014: 

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0093298

9. Stress and Cognitive Workload: https://www.nap.edu/read/5436/chapter/8#152

10. The Use Of Pilot Rating In The Evaluation Of Aircraft Handling Qualities by George E. Cooper ,April 

1969,NASA TN D-5153.

11. Miller, S. (2001). Workload Measures Technical Report, N01-006. Iowa City, IA, USA. University of Iowa. 

http://www.nads-sc.uiowa.edu/publicationStorage/200501251347060.N01-006.pdf

12. Scheuring, R.A., et al. (2007). The Apollo Medical Operations Project: Recommendations to Improve 

Crew Health and Performance for Future Exploration Missions and Lunar Surface Operations. 

NASA/TM–2007–214755. https://www.nasa.gov/wpcontent/uploads/2015/05/medical_distributed_planning_systems_lessons_learned.pdf

13. Uri, J. (2020). The Real Story of the Skylab 4 “Strike” in Space. NASA. 

https://www.nasa.gov/history/the-real-story-of-the-skylab-4-strike-in-space/

14. Parasuraman, R., and Riley, V. (1997). Humans and Automation: Use, Misuse, Disuse, Abuse. Human 

Factors, 39(2): 230-253.

15. Warm, J.S., Parasuraman, R., and Matthews, G. (2008). Vigilance Requires Hard Mental Work and Is 

Stressful. Human Factors, 50(3): 433-441.

11/13/2023

Rev C 13