Human Factors in the Design of Tactical Display Systems for the Individual Soldier (1995)

The previous chapter highlighted some of the conditions of the operating environment that affect the infantry. This chapter examines the characteristics of the infantry soldier such as cognitive capabilities and anthropometrics, personnel selection criteria, and performance design issues.

The advent of the 21 CLW concept raises the traditional MANPRINT question: Can this soldier with this training perform these tasks to standard under battlefield conditions? The employment concept portion of the Operational Requirements Document (ORD) for the Land Warrior System states: “The system will be employed by dismounted light, airborne and air assault soldiers, M113 and Bradley fighting vehicle (BFV) crewmen, Marines, and special operations forces (SOF) to execute the infantry's mission.” However, the report is limited to Army dismounted infantry personnel who are currently in the Army or will be by the year 2000.

Soldiers are recruited from the general population in accordance with prescribed cognitive, medical, and physical standards (height, weight, and strength).¹ In fiscal 1994 the Army enlisted 68,000 recruits, of whom approximately 63,000 did not have prior service experience. About 10,000 were assigned to the infantry career management field (CMF). The Army uses high school degree and the Armed Forces Qualification Test (AFQT), which is a subset of the Armed Services Vocational Aptitude Battery (ASVAB), as quality measures. As a matter of policy, the Army can change the distribution of quality within the force. The subsections below describe the infantry population based on current quality criteria.

Although high school graduation and ASVAB scores are useful measures of quality and have been shown to correlate with performance in military jobs (Wigdor and Green,

important as the nature of the tasks become more complex and information intensive. Specifically, work should be accomplished to examine the human abilities that make a difference in soldier performance on the Land Warrior System. Once these are defined, existing selection tests can be identified or new ones developed for measuring these abilities.

In 1982 the Army conducted a study using Fleishman's (1975) human performance taxonomy to determine the degree of difficulty associated with performing tasks in 20 new systems (U.S. Department of the Army, 1992). This study, known as the “Complexity Study,” was successful in predicting performance and has been validated through staff studies conducted at the Pentagon. Research that builds on these results should be vigorously pursued by the Army. The taxonomy proposed by Fleishman is presented below as a guide to identifying useful criteria.

The ASVAB is composed of 10 subtests: general science (GS), arithmetic reasoning (AR), word knowledge (WK), paragraph comprehension (PC), numerical operations (NO),

coding speed (CS), auto shop (AS), mathematics knowledge (MK), mechanical comprehension (MC), and electronics information (EI). Verbal ability (VE), which is considered an eleventh subtest, is a composite of word knowledge (WK) and paragraph comprehension (PC). All ASVAB tests except for numerical operations and coding speed are power tests instead of speed tests and have generous time limits.

All men and women entering the armed services must take the AFQT, which is a composite of ASVAB subtests: the formula is 2 × verbal ability (VE) + mathematics knowledge (MK) + Arithmetic Reasoning (AR). Scores range from 0 to 100. The average is 50 and the minimum score for service is 10. Test results are divided into five test score categories: I, II, III, IV, and V, and III is further divided into IIIA and IIIB. Categories I-IIIA represent the upper half of the population. Federal law prohibits anyone scoring in category V from entering the armed forces and restricts the number of category IV recruits to no more than 20 percent of the annual enlistees.

The Army sets quality targets for all enlistments and all career management fields. The Army-wide AFQT targets for fiscal 1994 were 67 percent I-IIIA, 31 percent IIIB, and 2 percent IV. The infantry targets were 64 percent I-IIIA, 33 percent IIIB, and 3 percent IV, but the infantry actually received approximately 68 percent I-IIIA, 28 percent IIIB, and 4 percent IV enlistees. The National Guard is not required by law to meet the category IV standard that the active component is required to meet; however, over the last 3 years, it has voluntarily met the 2 percent category IV goal.

Although a high school degree is not technically a requirement for enlistment, the competition is such that it is a requirement for all practical purposes. In fiscal 1982, Congress placed a 35 percent ceiling on male non-prior service, non-high school graduates. In fiscal 1994, 95 percent of the recruits were high school graduates, which was the goal. About 85 percent of the Army National Guard recruits have high school diplomas. A high school degree is a good predictor of the likelihood of enlistment completion.

Each service establishes its own composites of the ASVAB subtests to satisfy job structure and mission requirements. Applicants are classified in a military occupation by using these composites to predict success in initial occupational training schools. The Army composites from the ASVAB subtests and corresponding aptitude areas are shown below:

Scores on the ASVAB range from 40 to 150. The average is 100, and the minimum score to be accepted for given raining is 85.

In addition to the Army entrance requirements, the following specific requirements have been established for soldiers, who must be male (U.S. Department of the Army Regulation 611-201, 1994):

1. a physical demands rating of very heavy;

2. a specific physical and medical profile (see below);

3. color discrimination of red/green.

4. correctable vision of 20/20 in one eye and 20/100 in other eye;

5. a minimum score of 90 on aptitude test (of the ASVAB) for combat;

6. formal training under the auspices of the Infantry School (completion of 11B course).

Some positions require more use of tactical information systems than others, such as a special forces sergeant. These individuals enter the career field after they are in the Army. Candidates for this rank and status, which is also closed to women, must meet the above requirements as well as the following:

1. a minimum score of 110 in general technical aptitude and 100 in combat aptitude;

2. “secret” security clearance;

3. completion of Special Forces Qualification Course (SFQC) formal training course;

4. meeting requirements listed in Army Regulation 614-200;

5. U.S. citizenship.

Rangers, like special forces sergeants, are also likely to need high-grade tactical information, but there is no separate career field for Rangers. Army personnel assigned to Ranger battalions are selected after they are in the Army; their requirements are very demanding.

The physical requirement for the infantry do not differ from those for all Army personnel. The physical demands for infantry soldiers include the following:

• occasionally raise and carry 160-pound persons on back;

• frequently perform all other tasks while carrying a minimum of 65 pounds, evenly distributed over entire body; miles;

• frequently walk, run, crawl, and climb over varying terrain for a distance of up to 25

• frequently give oral commands in outside area at distances up to 50 meters;

• able to hear oral commands in outside area at distances up to 50 meters;

• occasionally climb a rope a distance of up to 30 feet;

• frequently throw 1-pound object 40 meters;

• frequently visually identify vehicles, equipment, and individuals at long distances.

The physical profile also refers to functional capacity to perform as determined by medical personnel in six areas: physical capacity, upper extremities, lower extremities, hearing-ears, vision-eyes, and psychiatric. These areas are always presented in the same order. A score of 1 is normal and 4 is deminished performance. The required physical profile for an entry infantry soldier is translated as follows:

• physical capacity (1)--good muscular development with ability to perform maximum effort for indefinite periods;

• upper extremities (1)--no loss of digits or limitation of motion; no demonstrable abnormality; able to do hand-to-hand fighting;

• lower extremities (1)--no loss of digits or limitation of motion; no demonstrable abnormality; be capable of performing long marches, standing very long periods;

• hearing-ears (2)--audiometer average level of six readings (three per ear) at 500, 1000, 2000 Hz or not more than 30dB, with no individual level greater than 35dB at these frequencies and level not more than 55dB at 4000Hz; or audiometer level of 30dB at 500 Hz, 25dB at 1,000 and 2000 Hz, and 35dB at 4000 Hz in better ear (poorer ear may be eaf);

• vision-eyes (2)--distant visual acuity correctable to 20/40-20/70, 20/30-20/100, 20/20-20/400;

• psychiatric (1)--no psychiatric pathology; may have history of a transient personality disorder.

Allowing less than perfect vision requires that the Land Warrior System accommodate soldiers who wear glasses. This challenge is compounded for older soldiers wearing bifocal lenses. Optical inserts in the chemical protective mask are not bifocal.

Results from the 1992 Youth Attitudinal Tracking Survey (Lehnus, 1994) show a decline in the propensity to enlist. As recruiting becomes more difficult, quality may be traded off in order to meet accession numbers. The demand for the best and brightest will continue to rise in the private sector as well. As the economy and job opportunities improve, the competition for high quality personnel will increase.

Although it has been rumored that the force is getting older, the facts provided by the Army do not support this notion. The average age of the active force is 20.4 years and has been relatively constant over the last 10 years. (No data were gathered on the Army Reserve or National Guard.)

The probability of soldiers for whom English is a second language is likely to increase with current and projected immigration trends.

Army training addresses both individuals and groups. Individual training teaches soldiers the basic skills required for individual survival and job performance on the battlefield. Group training prepares soldiers to perform tasks as part of a team. Most individual and some group tasks are taught as part of basic and advanced individual training, while some individual and most group training is conducted in units. Training time demands exceed available time to train, so unit commanders set priorities for training time on the bases of their missions' essential task list and training needs assessments.

Demanding and realistic training builds confidence and cohesion. Resource limitations often reduce the amount of training that is provided as part of fielding new equipment. As a result, the quality of training deteriorates over time.

Work by the Army Research Institute has shown that cognitive passive tasks--such as those involving the accurate recall of subject matter with little or no behavioral component (e.g., a pilot pre-flight checklist) have high skill decay rates and require more sustainment training than other tasks to maintain proficiency. The Land Warrior System will have a large number of cognitive passive tasks at the leader levels. To the extent possible, the number of these tasks should be minimized.

Although embedded training systems can help alleviate many training problems, the computer hardware, space, power, system architecture, and additional weight requirements must be considered as part of the total system design process. Some specific hardware and software features associated with installing and operating an embedded training system include processing speed, access rate, memory, display capabilities, communications, interfaces, menu structures, and the performance data collection capabilities. Planning for such a system must include an analysis of the conditions of use (e.g., conducting embedded training for one platoon while another is conducting operations in a combat zone). More significant will be the cost associated with designing and acquiring a fully embedded training system. The demand for field expedient technique training to overcome system failures will be present.

The ORD cites the minimum personnel requirement for the Land Warrior System as follows (personnel communication): “No qualitative or quantitative changes in personnel

requirements will result from fielding the land warrior. No new military occupational specialties (MOSs) will be required for operators and maintainers.”

At the leader level, the infantry has a higher percentage of category IIIB and IV sergeants (approximately 37 percent of the total) and staff sergeants (approximately 41 percent of the total) than the overall force (U.S. Army Natick RD&E Center, 1994). Retention results in sergeants who may have not scored as high as new recruits on the ASVAB. As the propensity of young males to enlist goes down, the challenge to maintain quality will become more difficult.

The implications of this situation are significant. Potentially, the greatest cognitive workload is on the fire team and squad leaders, who may be the least able to manage it. It is questionable as to whether the majority of sergeants of tomorrow will possess the cognitive abilities and skills necessary to operate as envisioned and thereby capitalize on the new capabilities provided by land warrior technology.

Approximately 33 percent of the infantrymen who will use the Land Warrior System will be in categories IIIB and IV. These categories can be expected to read at a 7th grade level, which does not promise speedy information processing time. Display contrast resolution that does not meet the international standard (ANSI/HFS 100-1988) will negatively affect reading speed. The hearing and vision limitations of current and future soldiers will have to be accommodated by the design.

Maintenance personnel for the Land Warrior System are not addressed in the target audience description. The ORD does require that there be no increase to entry level requirements for maintenance MOSs 31V and 39E. The maintenance implications on the quality of the force might be offset by contractor provided maintenance. A fully integrated system will require careful Built-in Test/Built-in Test Equipment design to facilitate fault isolation and repair or replacement.

The Army's historical experience with new technology has demonstrated unintended effects, such as increases in demands for soldier quality, increased school training time, skill creep, or lower equipment readiness levels. The trade-offs associated with changing personnel selection criteria, quality distribution, and training all have long-term cost implications for the design of the Land Warrior System.

One of the questions that arises is the degree to which the new display system will be adjustable to the individuals who will use it (see Gordon et al., 1988). Will display units be interchangeable among individuals, or are they to be tailored for individual soldiers? Does individual tailoring have a strong link to security questions, that is, lock-out of enemy access? The answers to these questions might dictate the approach taken in terms of anthropometric design.

Traditional anthropometry is a measurement and classification procedure that allows for the design of individual items to proceed around known physical characteristics of the population sample under consideration (i.e., each dimension of the human body). Such approaches try to provide the best compromise between statistical norms for a group and the unique attributes of individuals. Intelligent design (e.g., modularization) can allow for customization even if the basic configuration is developed on a group basis.

The basic considerations of anthropometry and biomechanics are the form and fit of the item under consideration. Some biomechanical factors include the requirement that any head-mounted device must consider the question of weight and prolonged use as they affect muscular fatigue. Likewise, the designers of hand-held devices also need to consider anthropometric factors, especially if data entry is to be provided through keyboard systems. In a military context, it is relevant to consider use of hand-held devices with gloves as an issue that requires careful anthropometric design. Again, in context, voice entry while wearing some form of mask or exclusion garment may prevent optimal use of critical systems. Thus, decisions concerning conditions of use raise any number of questions concerning the fit between operator and device.

The current target audience description does not cite head dimensions as critical. Given the importance of a comfortable fit to the soldier, the current design specification for 5-95th percentile males leaves out 10 percent of the population. The table below shows the difference between 5th-95th percentile and the 1st-99th percentile on a few head dimension measurements. The differences are so small that the needed adjustments should be easy to achieve. Because helmet stability is critical to maintaining a stable image, changes in the requirements seem appropriate. This change is particularly significant given the history of importance of micro-anthropometrics in the design of aviators ' helmets and head-mounted displays.

Soldiers' acceptance of the Land Warrior System displays will be driven by their confidence in their ability to use the devices effectively under adverse conditions, the devices's attributes, and their views of the need for it in light of everything else that they have to carry into battle. Interviews with the Rangers who tested the prototype revealed that they valued three components of the system: squad radio, global position satellite system (GPS), and the thermal sight. These components were valued because the provided needed capabilities that were previously not available. Other components were not considered as useful because they did not work reliably, were too heavy or uncomfortable, or did not improve performance. Despite the fact that there were problems that clearly biased the test personnel, they were clear in what they thought added value. These data are primarily anecdotal, based on experiences in a preliminary, uncontrolled field test.

A soldier's confidence in a new system is a function of his proficiency, which is in part determined by how much training he has received and the complexity of the system. These factors are interrelated. The more complex the system, the more training a soldier will need to gain and sustain proficiency. Sufficient training is often not provided, for resource reasons. As a result, soldiers require a longer period of time to gain confidence in a system, if ever. Research by S.L.A. Marshall (1947) established that a large percentage of soldiers do not fire their weapons in combat. If a soldier is not proficient with the system, he will not risk exposure to enemy fire. The Land Warrior System offers a solution to this problem by letting a soldier fire accurately while not exposing himself to enemy fire. At the same

time, the Rangers reported that battlefield mobility was reduced by the night vision system. The complete and integrated Land Warrior System will be perceived to be complex.

When new systems are effective and well used, they can become a crutch without which the soldier or unit falls to respond. In the early days of TACFIRE (an artillery tactical fire control system), some artillery unit commanders found that their units would not respond to a call for fire when TACFIRE was inoperative. The personnel had become so dependent on TACFIRE that they had lost the ability to fire without it. Overreliance on technology can make a unit vulnerable if field-expedient training is not conducted.

Soldiers generally expect that a new system will have the following attributes: effective; reliable; simple to operate, repair, and maintain; reduce workload or improve effectiveness; and fit comfortably. For the infantry soldier, if a new system does not help him shoot, move, communicate, or survive, it may be dropped along the march in order to lighten his load.

Many leader tasks may be made easier with the Land Warrior System. For instance, reporting could be done photographically. Although this eases the workload associated with reporting, it may drastically increase the workload for those who receive and must interpret messages. However, the new system will require the mastering of some level of operator and maintenance tasks. The danger is that it creates a demand for information that requires the squad leader to change what he does and how he does it. The impact could affect the survivability or effectiveness of the squad when the leader's attention is not properly distributed.

Comfort is an essential ingredient to an infantry soldier who is carrying a heavy load and usually involves form, fit, weight, and balance. Proper fit contributes to confidence. Conversely, a poor fit leads to frustration and anger. Soldier frustration with the initial prototype was reported to be very high.

Providing remedies to the problems of cognitive or information overload is not easy because of the various factors that affect work and the variations in emotional reaction to a variety of perceived risks, physical demands, and surprise. Technology is not the only cognitive workload driver and may not be the principal one; communication and coordination tasks are major workload factors. Job tasks not related to a system impose significant workload. There is no doubt that workload will go up as a result of the Land Warrior System because new tasks will have to be performed that have not been performed previously. The question is one of penalties and payoffs.

The complex technology and all-pervasive impact of the proposed Land Warrior System on infantry soldiers raises a number of basic issues and design considerations. The proposed concept raises doctrine questions about the autonomy of the individual soldier and raises a question concerning current individual skills and training requirements.

The requirement that no qualitative or quantitative changes in personnel requirements are to result from fielding the Land Warrior System (U.S. Department of the Army ORD, 1994) will be an engineering design challenge. Contractors will have to translate this requirement into engineering criteria. Human factors engineers will want to know about user work requirements associated with: field of view, field of regard, resolution, polarity, contrast, brightness, etc. Furthermore, human factors engineer will want to know about soldier ability requirements, such as: spatial orientation, perceptual speed and accuracy, visual acuity, division of attention, eye dominance. Design engineers will want to know system requirements, such as: What is the required field of view? What is the mean time between failures? How much accuracy is required? The software programmer will want to know: What information is required and when? What is the required rate for updating data? What is the required refresh and update rate of the display? What is the definition (pixel by pixel) of symbols? What control mechanisms accomplish what actions? Engineering psychologists will be concerned about degraded stimulus conditions, multiple input channels, pattern recognition, attention allocation and control, and individual differences. Answers to these questions are contingent on the tasks performed, the conditions of performance, the measures of effectiveness used, and the level of proficiency required (Zubal et al., 1990; 1993)

Ultimately the success or failure of the Land Warrior System will depend on the individual soldier. There is a broad bandwidth of individual differences in the youth population and large variances around specific cognitive, physical, and psychomotor measures. Historically, personnel selection and soldier training have been used to mitigate this naturally occurring variance. Effective personnel selection requires knowledge of the human attributes that correlate with successful performance on the new system. For the Land Warrior System, little is known about the relationship between design attributes, human attributes, and successful performance.

Training time is limited. Embedded training solutions can assist if the hardware and software requirements needed are considered in the specifications for computer memory, processing speed, input and output devices, display characteristics and system architecture. The current space, weight, and power constraints may restrict the effectiveness of an embedded training solution.

New equipment must fit properly and comfortably if soldiers are to use them willingly. Careful consideration needs to be given to ensuring that the design meets the anthropometric and biomechanical requirements of the user population. In the case of the helmet-mounted design, comfort and stability are dependent on design. The fit of the helmet may provide an unstable platform for the dismounted infantry soldier. This issue warrants attention.

The amount of information that the Land Warrior System will provide to the individual soldier may be orders of magnitude greater than the information now provided. The target audience description shows that a large number of potential infantry squad leaders are in the lower mental categories of military personnel and can be expected to read at a 7th grade level. The ability of these personnel to perform successfully needs to be closely evaluated. The cognitive burden is likely to be placed on the two least experienced leadership positions in the platoon--squad leader and platoon leader.

Potentially, the Land Warrior System will significantly alter traditional roles, functions, relationships and employment concepts. These changes will affect soldier performance and personnel selection.