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4
Stress
The battlefield environment is a stressful place and, as graphically de-
scribed by Keegan (1976), those stresses are amplified within the armored
vehicle. Indeed, the post-transition phase of any team situation will impose
a substantial degree of stress, incorporating time pressure at a minimum,
often augmented by danger, noise, and a host of other environmental stres-
sors. The concept of stress as it influences human performance may be
understood in the context of Figure 4.1. At the top of the figure are identi-
fied a set of stressors; these are influences on information processing and
cognition that are not inherent in the content of the information itself. Stressors
may include features of the work environment like noise, vibration, heat,
dim lighting, and high acceleration, as well as such psychological factors as
anxiety, fatigue, and danger. Such stressors may have different manifesta-
tions: subjective experience, physiological changes, and performance dec
remeets.
Stressors may affect a subjective experience. For example, individuals
are usually (but not always) able to report a feeling of frustration, or arousal,
as a consequence of a stressor. Closely linked, a change in physiology is
often observable. This might be a short-term change- such as the influence
on heart rate associated with the demands of flying as pilot-in-command
(Hart and Hauser, 1987) or the stress of controlling air traffic in high-load
situations (Romhert, 19799. Or it might be a more sustained effect, such as
the change in the output of catecholamines, measured in the urine, after
periods of simulated combat maneuvers flying in an F16 (Burton et al.,
1977), inflight emergencies, or actual battlefield events (Bourne, 1971~.
94
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STRESS
95
The subjective and physiological characteristics are often, but not invar~antly,
linked. The subjective experience of stress may also mediate performance.
For example, one who does not realize the risk or danger of a particular
situation will experience less stress than one who does a subjective ap-
praisal of the situation, thereby mediating stress effects on performance
(Coyne and Lazarus, 1980J.
As Figure 4.1 shows, the effects may be either direct or indirect. Direct
effects are stressors that influence the quality of information perceived by
the human operator or the precision of the motor response. For example,
vibration will reduce the quality of visual input (as well as the quality of
motor output), and noise will do the same for auditory input. Time stress
may simply curtail the amount of information that can be perceived, in a
way that will quite naturally degrade performance. Direct effects also in-
clude the effects of noise on working memory (Poulton, 1976~; rehearsal of
a set of instructions or coordinates, for example, will be more difficult in
noise. Direct effects can also include the distraction experienced by an
operator who is concerned about personal problems or danger, who may
therefore redirect attention to thinking about those problems, rather than to
the job at hand.
Some direct-effect stressors (e.g., noise or vibration) as well as others
for which no direct effect can be observed (e.g., anxiety or fear) also influ-
ence the efficiency of information processing. In this chapter we first con-
sider stressors that are characteristic of the physical work environment in
which the tank crew operates, described in Chapter 1. We then address
what is known about the effects of psychological stress on performance
Direct. . .
E.g., lighting,
noise, heat,
vibration
INPUT
STRESSORS
' Indirect...
`` E.g., anxiety,
~ fear, fatigue
1,
INFORMATION
PROCESSING
FIGURE 4.1 Influence of stress on human performance.
Direct...
E.g., heat,
vibration
~ ,
~ BEHAVIOR
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96
WORKLOAD TRANSITION
under conditions of high anxiety and arousal. Finally, we consider stress in
the context of team performance, examining the characteristics of teams
that make them more stress resistant. The discussion emphasizes to a greater
extent the stress effects present in the post-transition period. In Chapter 5
we consider the most potent stressors of the pretransition period: sleep loss
and fatigue and their influence on both pre- and post-transition performance.
STRESS IN THE WORK ENVIRONMENT
The term work environment encompasses all the variables that deter-
mine the physical comfort level of users. These include ambient tempera-
ture, relative humidity, atmospheric pressure, airflow, the presence or ab-
sence of noxious fumes or toxic substances, motion, acceleration (normally
expressed as G-loading), and ambient sound and light levels. For most of
these parameters there exist absolute limits within which humans can func-
tion and beyond which they cannot function or, for some variables, even
survive. There are, in general, much narrower limits within which humans
feel comfortable. An example of such a comfort zone is contained in the
American Society of Heating, Refrigerating, and Air-Conditioning Engi-
neers (ASHRAE) comfort standard (American Society of Heating, Refriger-
ating, and Air-Conditioning Engineers, 1985~. The definitive military hu-
man factors standard, MIL-STD-1472C (U.S. Department of Defense, 1981),
specifies such zones for several environmental variables.
The degree to which comfort enhances performance is a function of the
nature of the tasks that must be completed. The differential effects of many
environmental factors have been demonstrated on the performance and physical
workload of various types of tasks. There are well-known relationships
between certain environmental variables, such as ambient temperature and
relative humidity and the ability to do physical work (Occupational Safety
and Health Administration, 1974~. Among the factors known to increase
workload or, more accurately, to decrease performance are high levels of
ambient noise (Davies and Jones, 1982), high temperature and humidity
(Hancock, 1981), low temperature (Enander, 1984), and motion and vibra-
tion (International Organization for Standardization, 1978~. Obviously, high
levels of toxic materials in the environment can have a substantial impact
on the user's ability to perform tasks.
The tank environment combines some of the most potent factors that
have been shown to adversely affect performance. Even in a nonchemical/
biological-warfare (non-CBW) battlefield scenario, tank crew members are
subjected to elevated temperature and humidity due to the fact that tanks are
not air conditioned. Heat casualties are quite common during training in
field exercises. It is also common for the interior of the tank to be filled
with noxious fumes from leaking hydraulic fluid and spent propellant from
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STRESS
97
ordnance. When buttoned up, the interior of the tank is pressurized by an
air movement system that brings outside air in through filters that remove
particulate and some chemical components. This air is not conditioned for
temperature or humidity. In the COW battlefield environment, these condi-
tions are exacerbated by the requirements of wearing environmentally pro-
tective clothing or "MOPP gear" and remaining buttoned up inside the tank
for long periods of time.
Even in non-CBW environments, all crew members must wear helmets
with integral earphones and a movable microphone. The purpose of these
helmets is not so much to protect crew members from external ordnance as
it is to protect them from head injuries caused by hitting the interior surface
of the tank while it is moving over terrain. The large, fully enclosing
earphones insulate the crew members from noise generated by the tank
running gear. The helmet allows crew members to communicate with each
other and with other tanks in their platoon. Unfortunately, the helmets are
heavy and tend to trap heat. The earpieces press against the sides of the
head causing discomfort after even short periods of time.
It is reasonable to infer that environmentally extreme conditions will
affect some tasks more than others. Some tank crew positions are primarily
physically oriented, i.e., those of loader and driver, whereas others are con-
cerned mainly with cognitive tasks, i.e., those of gunner and tank com-
mander. However, even those crew positions that are physically oriented
have task responsibilities that require mental sharpness. Specifically, all
crew members are expected to search for threats and targets. During opera-
tions of long duration, the crew is put on a sleep-wake cycle that requires
all crew members to assume the responsibility of searching for enemy threats.
The result of this division of responsibilities is that adverse environmental
factors are likely to increase the workload of all tank crew members and,
consequently, decrease the performance of the tank crew as a whole.
Long-duration operations also bring into play another environmental
factor that should be noted. Tanks contain no toilet facilities. When but-
toned-up, crew members are not allowed to leave the confines of the tank.
The unpleasant, but inevitable result of these restrictions is that all bodily
functions must be accommodated within the tank. It is probably an under-
statement to observe that such a situation can lead to an environment that is
not conducive to superior task performance.
STRESS AND HUMAN PERFORMANCE
Many aspects of the relation between stress and performance are related
to the construct of arousal. The relation between stress-induced arousal and
performance has sometimes been described in terms of an inverted U-shaped
function, as shown in Figure 4.2. With increasing arousal, performance
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Representative terms from entire chapter:
workload transition
98
Optimum Level
of Arousal
o
a)
//
//
WORKLOAD TRANSITION
Simple Task
\
\~
STRESS
99
cognitive effort or resources mobilized for task performance. In contrast,
the downward limb is the consequence of a more specific effect of high
arousal on the selectivity of attention, which causes the operator to focus on
a more restricted set of environmental or internal sources of information.
An appropriate metaphor is to say that high levels of stress narrow the
spotlight of attention.
Extending this argument logically leads to the conclusion that high
arousal should be more detrimental to tasks that require the processing of
several information sources (i.e., complex tasks) than to tasks which depend
on only a few cues (i.e., executing a well-practiced skill). This difference
in arousal effects resulting from task complexity is depicted by the differ-
ences between the two curves in Figure 4.2. The optimum level of arousal
for the simple (or the more highly practiced) task is higher than for the
complex task.
A relevant example of the different effects of stress on performance as
a function of complexity is an experiment carried out by Berkun (1964~.
Using Army soldiers engaged in simulated (but highly realistic) tasks, Berkun
employed three different experimental manipulations to induce a very real-
istic experience of stress. In one manipulation, subjects were led to believe
that the aircraft in which they were flying was in danger of crashing as
they attempted to fill out an insurance form. In a second manipulation
imposed during combat exercises, subjects were led to believe that artillery
shells were exploding around them as a result of a confusion about their
location, as they tried to follow procedures to initiate a radio call to redirect
the fire. In the third manipulation, subjects believed that a demolition that
they had initiated had accidentally caused a serious injury to one of their
fellow soldiers, and they were now required to call for medical assistance.
Thus, in all cases, subjects were deceived to believe that they, or someone
for whom they felt responsible, were at serious mortal risk. Berkun found
that in all three cases, the high level of stress and arousal induced by the
anxiety or perceived danger led to degraded performance on following the
necessary procedures. However, this degradation was less for soldiers with
greater experience. This last finding may be placed nicely into the context
of Figure 4.2, if it is assumed that the more skilled soldier faces a less
complex task in problem solving. Much of the perceptual and short-term
memory requirements of task solution are replaced by direct recall from
long-term memory. The increased arousal caused by stress then exerts a
less degrading effect.
While Berkun's study clearly illustrates the loss of performance under
stress, it is less illuminating regarding the qualitative manner in which per-
formance is affected. This issue of qualitative stress effects will now be
addressed in more detail.
100
WORKLOAD TRANSITION
QUALITATIVE PATTERN OF STRESS EFFECTS
Hockey (1984, 1986) expanded on the two factors (arousal and tunnel-
ing) that underlie the Yerkes-Dodson law and has attempted to identify
more subtle patterns of stress effects on performance. Reviewing a large
number of studies that examined the effects of stress on human perfor-
mance, Hockey distilled the pattern of stress effects into the form shown in
Table 4.1. Each stressor appears to be identified by a profile or signature of
effects across a set of five critical information processing components: general
arousal, selectivity of attention, speed and accuracy of performance, and
capacity of short-term memory (working memory).
The focus in this section is on a stressor that is an important character-
istic of many operational environments in the team transition situation: the
anxiety, fear, or arousal associated with failures of task performance or
dangerous' threatening environments (Idzikowski and Baddeley, 1983a, 1983b).
This fear is often coupled with a shortage of time to deal with the crisis.
(The direct effects of time pressure on performance were discussed in some
detail in Chapter 3.) This stressor may characterize the experiences of the
flight crew, following an engine stall in midair in which both danger and
time stress are imposed; the nuclear control room personnel, following ini-
tial alerting of a failure; or the tank crew moving into combat. Idzikowski
and Baddeley (1983a, 1983b) present a review of research and case study
findings related to this form of stress; the reader can refer to treatments by
Hamilton and Warburton (1984), Broadbent (1971), and Hockey (1986) for
broader discussions of stress. In the following review of research, we also
capitalize on the psychological equivalence of signature patterns between
noise and anxiety as shown in the table, allowing us to extrapolate from the
effects of noise to those of danger-producing anxiety. It is reasonable, also,
to assume that in the noisy and dangerous environment of the tank, these
two effects would be additive. In the following discussion, we use the term
stress to refer to the combined effects of danger, anxiety, and noise. Within
the framework of teams in transition addressed in this report, the transition
effects involve a rapid jump from the left to the right side of the Yerkes-
Dodson curve. Our focus in Chapter 5 is on the left side of the curve. Here
we address performance effects on the right or high end.
Attentional Tunneling
Weltman et al. (1971) compared the performance of two groups of divers
on a central and peripheral signal detection task. One group was led to
believe it was under conditions of a 60 foot dive in a pressure chamber; the
other was not. In fact, there was no change in pressure for either group.
Both groups showed similar performance on the central task, but perfor
STRESS
TABLE 4.1 The Patterning of Stress Effects Across Different
Performance Indicators.
101
Performance Indicators
Speeded Responding
GA SEL S A STM Sources/Reviews
Noise
Anxiety
Incentive
Stimulant drugs +
Later time of day
Heat
Alcohol
Depressant drugs
Fatigue
Sleep loss
Earlier time of day
+ + O. -
+ + O -
+ + + + +
+ + O -
+ _ _
+ O
+ O - O
_ O
o
+ +
2,3,4,5,7,8
4,12
2,4,5
2,4,13
1,2,4,5,6,8
2,4,11
2,4,7,8,13
2,4,10,13
2,4,9
2,4,5,7,8
1,2,4,5,6,8
The table summarizes the typical outcome in various studies using these stress variables in
terms of their effect on the five behavioral indicators show: GA general alertness/activation
(subjective or physiological arousal); SEL - selectivity of attention; S and A refer to overall
speed and accuracy measures in speeded responding tasks; STM short-term memory. A
plus (+) indicates a general increase in this measure, a zero either no change or no consistent
trend across studies, and a minus (-) a general tendency for a reduction in the level of the
indicator. A question mark is used to indicate cells where there is insufficient data. Sources
of data: (1) Blake (1967a, 1971); (2) Broadbent (1971); (3) Broadbent (1978); (4) Davies &
Parasuraman (1982); (5) M.W. Eysenck (1982); (6) Folkard (1983); (7) Hamilton, Hockey, &
Rejman (1977); (8) Hockey (1979); (9) Holding (1983); (10) Johnson and Chernik (1982); (11)
Ramsey (1983); (12) Wachtel (1967, 1968); (13) Wesnes and Warburton (1983).
SOURCE: G.R.J. Hockey, "Changes in Operator Efficiency as a Function of Stress, Fatigue,
and Circadian Rhythms." P. 44-39 in K.R. Boff, L. Kaufman, and J.P. Thomas (eds.), Hand-
book of Perception and Human Performance. Chichester, England: John Wiley and Sons,
1986. Reprinted by permission.
mance on the peripheral task was significantly degraded for the pressure
group. This group also showed greater anxiety-related increases in heart
rate, substantiating the increased level of stress. Stress may also cause a
focusing of attention on one particular task or cognitive activity, as well as
on a particular perceptual channel. In the analysis of cockpit voice record-
ings at times of high stress prior to accidents, Helmreich has found evi-
dence of severe breakdowns in the pilots' ability to handle multiple tasks or
multiple concerns.
Although perceptual or cognitive tunneling produced by stress usually
degrades performance, it is also possible to envision circumstances in which
this tunneling may actually facilitate performance, in which focused atten
102
WORKLOAD TRANSITION
lion on critical task aspects is desired. Indeed, this positive effect was
observed in a study by Houston (1969), who found that noise stress im-
proved the focus of attention on the relevant aspect of a stimulus and re-
duced the distracting effect of irrelevant aspects.
Data provided by Houston's experiment and others suggest that the
attentional or cognitive tunneling resulting from stress is defined in terms
of subjective importance or priority. That is, performance of those tasks or
processing of that information thought to be most important remains unaf-
fected or perhaps is enhanced (through arousal), while processing informa-
tion with lower perceived priority is filtered (Bacon, 1974; Broadbent, 1971~.
In one sense, this kind of tunneling is optimal, but it will produce undesir-
able effects if the subjective importance that defines the attended channel
proves to be unwarranted. Such was the case, for example, in the incident
of the Three Mile Island nuclear power plant (Rubinstein and Mason, 1979~.
Immediately after the crisis in the plant developed and under the high stress
caused by the initial failure, the operators appeared to be fixated on a single
faulty indicator, supporting an incorrect belief that the water level in the
reactor was too high, thereby preventing their attention from focusing on
more reliable indicators that supported the opposite (and correct) hypoth-
esis. As suggested by this example and elaborated below, this narrowing
effect can be directly related to biases in decision making. But for the
operator who has a well-structured and accurate model of task demands and
a well-developed skill in discriminating sources of useful (versus trivial)
information, it can be expected that stress should lead to little degradation
of performance, as reflected by the behavior of the United Airlines flight
232 crew (Predmore, 1991~.
Working Memory Loss
Mandler (1979) has discussed the degrading effects of anxiety on work-
ing memory. Correspondingly, many of the difficulties in following proce-
dures that Berkun (1964) observed when his Army subjects were placed
under the stress of perceived danger can also be attributed to reduced work-
ing memory capacity. Logie and Baddeley (1983) and Lewis and Baddeley
(1981) have noted similar working memory decrements of divers perform-
ing at depth. Idzikowski and Baddeley (1983a, 1983b) observed an anxiety-
related working memory loss of speakers waiting in the wings to give their
first public speech. Noise, as well as danger and anxiety, has also produced
consistent effects on working memory (Hockey, 1986~. While it is intu-
itively evident that the presence of noise would disrupt the ability to re-
hearse verbal information in working memory (Poulton, 1976), it appears
also that the combined stress effects of noise and anxiety may disrupt spa-
tial working memory systems as well (Stokes et al., 1990; Stokes and Raby,
STRESS
103
1989~. Indeed, in a simulation study of pilot decision making, Wickens et
al. (1988) observed that the effects of noise stress were greatest on decision
problems that relied on spatial visualization for their successful resolution.
Communications
Successful communications depend heavily on working memory, to re-
member what has just been said. Hence, it is not surprising that communi-
cations have sometimes broken down under conditions of stress. Analyses
of crew communications in accidents in which a prolonged inflight emer-
gency preceded ultimate disaster provide compelling evidence of the com-
munication breakdowns that occur under conditions of extreme threat. These
include fragmented communications, failures to process the information com-
municated, and inability to deal with multiple tasks or concerns (Predmore,
1991).
Long-Term Memory
While stress appears to disrupt working memory, it appears to have less
of an effect on the retrieval of information from long-term memory, to the
extent that information is well rehearsed and memorized. For example, in
their study of pilot judgment, Wickens et al. (1988) found that those judg-
ments requiring direct retrieval of facts from long-term memory were rela-
tively unimpaired by stress.
The differences in Berkun's findings between more and less skilled
soldiers is also consistent with this view. Stokes et al. (1990) found that the
decision-making performance of novice pilots deteriorated under stress, whereas
performance of a group of highly trained pilots in the same circumstances
was not affected. Presumably the latter group was more able to rely on
direct retrieval of information from long-term memory in making their deci-
sions.
Similar to the narrowing effect that stress exerts on perception and
selective attention, however, stress appears to restrict the information re-
trieved from long-term memory more specifically to those habits that are
well learned or overlearned (Eysenck, 1976~. Although there do not appear
to be much experimental data supporting this claim, at least one study
shows that increased stress actually eliminates some of the benefits of ex-
pertise and training in decision making (Ben Zur and Breznitz, 1981~. Studies
by Fitts and Seeger (1953) and Fuchs (1962) and analyses of aircraft acci-
dents carried out by Allnutt (1987) have all suggested that stress will lead to
a regression to earlier learned and more compatible response patterns, when
these patterns may conflict with incompatible (but appropriate) ones. Col-
lectively, these findings suggest the importance of extensive training in
104
WORKLOAD TRANSITION
procedures and actions that may need to be taken in emergency. They
further emphasize that such procedures should require only actions of high
compatibility. The findings, however, emphasize the extent to which cre-
ative innovative problem solving may be degraded under stress since, by
definition, such problem solving will not have been accomplished in the
same way in the past and hence repetitive practice of the same steps cannot
be achieved.
Strategic Shifts
There is some evidence from behavioral studies that stress leads to
consistent shifts in processing strategy. In the study of the anxiety brought
on by the first parachute jump, for example, Simonov et al. (1977) observed
a shift in detection performance that can be characterized by a riskier crite-
rion setting. The paratroopers were simply more likely to respond "yes"
and hence made more hits and more false alarms. Hockey (1986) concludes
that there is a general effect of noise and/or anxiety stress on the speed-
accuracy tradeoff, shifting performance to a less accurate but not slower
level. In their study of pilot judgment, Wickens et al. (1988) found that
judgments were less accurate but not necessarily slower under the combined
stress effects of noise, time pressure, and threat of loss of income.
The tendency of those under the stress of an emergency to shift perfor-
mance from accurate to fast (but error prone) responding has been cited as a
concern in operator response to complex failures in nuclear power control
rooms. The operator often has a desire to do something rapidly, when in
fact this impatience is often counterproductive until the nature of the failure
is well understood. In the Three Mile Island incident the hasty action of the
control room operators was to shut down an automated device that had in
fact been properly doing its job.
Decision Making
Understanding the effects of stress on decision making has always been
of great interest to the human factors profession. The importance of this
knowledge has been enhanced by the analysis of the faulty decisions made
in the Three Mile Island incident and, more recently, by concerns over the
decisions made in the U.S.S. Vincennes incident (U.S. Navy, 1988; see also
Chapter 81. Both of these incidents are particularly relevant to the focus of
this report because of the involvement of teams of operators in making
decisions following a fairly abrupt transition of system state, under a high
level of stress. The concern that decisions degrade under stress is rein-
forced by anecdotes and case studies of poor pilot judgments that have
occurred under stressful conditions of bad weather, spatial disorientation, or
STRESS
111
jumps, signaling the relief, as it were, that successful performance was
possible. In this regard, it is not surprising that, in a wide variety of
contexts, research findings demonstrate the efficacy of prestress training,
geared at providing preparatory information in order to reduce the novelty
of the stressful situation. Novelty, as Rose (1987) and others have indi-
cated, is a primary component of the intensity of the stress response: the
greater the novelty, the greater the intensity of the stress experienced in
many settings. Thus, training should be a crucial component of any pro-
gram to enable tank crews to manage stressful environments.
Finally, there appears to be considerable merit in training that makes
crews aware of the potentially degrading effects of stress. Survey data
collected from civilian and military flight crews using the Cockpit Manage-
ment Attitudes Questionnaire (CMAQ) contain items aimed at determining
attitudes regarding personal awareness of the effects of external stressors on
human performance. In particular, a Recognition of Stressor Effects subscale
of the CMAQ measures perceptions of personal capabilities when faced
with stressful conditions and the ability to put aside stresses caused by
personal problems when faced with the need to perform at high efficiency.
One of the striking findings from the survey data is how little awareness
flight crews have of the deleterious effects of stress on individual and group
performance (Helmreich, 1984~. The model pilot tends to endorse a posi-
tion reflecting an ability to leave behind personal problems and a perception
that personal performance is unaffected by life-threatening, emergency con-
ditions. Such attitudes represent the classic model of the "white scarf,'
aviator.
TEAM MODELS: IMPLICATIONS FOR STRESS MANAGEMENT
The bulk of the research on stress addresses individual-level responses
(physiological, psychological, and behavioral) often in laboratory settings
removed from the more complex contexts in which multiple stressors usu-
ally occur. Prevention and intervention programs are also often addressed
as individual-level strategies for reducing negative stress-related consequences
(e.g., therapy, exercise, training programs). Fewer studies examine the group
and organizational level structures and processes that might be modified in
order to diminish the problems created for individuals enduring a high level
of stress in the workplace. A simple example is the case with air traffic
controllers. Studies typically focus on the effects of the stress of their jobs
on their own responses, physiological and psychological (as well as on their
families). As Matteson (1987) suggests, stress may often be relieved, not
by training particular individuals in how to cope with stress, but by altering
the conditions that create the negative stress responses. Human and organi-
zational resources can be used, for example, to hire more controllers to
2
WORKLOAD TRANSITION
handle peak times and high volumes of traffic Kahn (1987) concludes a
recent review of stress research indicating optimism about the potential for
organizational-level interventions.
While research findings concerning the responses of individuals in vari-
ous occupations to stressful situations or encounters are important, perhaps
even more useful for the investigation of teams in transitions, such as tank
crew operations in stressful environments, are the studies of teams and
team-building strategies. Numerof (1987) and S. alas and coworkers (Baker
and Salas, 1992; Driskell and Salas, 1992; Tannenbaum et al., 1992) pro-
vide models of team characteristics that may be relevant to teams in a
workload transition. Teams are defined by Numerof as groups that have a
high level of energy directed toward accomplishing a goal, usually in set-
tings in which the tasks to be performed require multiple inputs and cannot
be handled by any individual alone, which is generally true of tank crews
during periods of engagement. Effective teams are referred to as groups
that have a combination of high loyalty, morale, commitment, adaptability,
and exchange and coordinate information. These good team qualities, which
may provide a buffer against organizational stress, include: effective lead-
ership, appropriate selection of members, commitment and cohesion, open
climate, achievement motivation, effective work methods, clarity of proce-
dures, giving and acceptance of constructive criticism, individual initiative,
high creativity, positive intergroup relations, and role clarity.
These characteristics are briefly described below, based on Numerof's
(1987) review. Various studies support the significance of the individual
components of the model, but what remains to be specified is the relative
impact of each component on team performance and the optimal mix. Ef-
fective leadership is viewed as one of the most important components, given
the wealth of research on this factor (see Chapter 10~. What appears to be
critical is the ability of the leader to change leadership style based on the
requirements of the situation and to integrate the needs and individual abili-
ties of the team members to meet the demands of the task situation. We will
expand on our discussion of this factor subsequently, given its significance
for team performance.
Appropriate selection of members refers to the extent to which the
individuals are well matched as a team to the task requirements. This
includes the match between each individual and the job requirements, or
what is referred to above as the job-person fit. This issue is discussed in
greater detail in Chapter 10 in the context of airline crews, on which there
has been a great deal of research involving the task and social skills re-
quired to maximize crew performance ire the cockpit in particular, to opti-
mize crew performance and decision-making skills under the high stress
produced by emergency situations.
Commitment and group cohesion are referred to frequently in the litera
STRESS
113
lure on group productivity and effective teams. The usual assumption is
that high levels of cohesion and commitment enhance group productivity.
While this is generally true (see review by Ridgeway, 1983), high cohesion
may also result in lower group productivity if the performance noes of the
group run counter to those of the overall organization (e.g., the normative
pressures in some work groups that limit work output or the rate of produc-
tion). Furthermore, highly cohesive groups may also be subject to the
problem identified by Janis (1972) as groupthink, situations in which group
members who offer information or criticisms that deviate from the more
popular decision in the group are ignored. According to Ridgeway (1983),
this high level of cohesiveness may cause groups to make poorer decisions
than they otherwise might. And yet highly cohesive groups often have more
trust in each other and coordinate their behavior more. It has been found
(Kelley et al., 1965) that outside stress makes it harder for members to trust
one another and coordinate their behavior together, which greatly increases
the social difficulty of the group's task, although some evidence provided
by Driskell and Salas (1991) suggests that this may not invariably be true.
Therefore, more cohesive groups whose members have good interpersonal
relationships should perform better under high stress conditions (Shils and
Janowitz, 1948~.
Many of the remaining team components are self-evident; thus, only
those that are less so are discussed. An open climate is critical because it
represents a team that has open direct communication and trust. In such
groups members often feel at ease in taking what they consider appropriate
risks, which in turn enhances opportunities for innovation and creativity.
Achievement motivation refers to the extent to which team members
are motivated toward performance goals and are willing to use feedback
mechanisms to improve performance over time. Individual initiative is also
an important component in effective teams since members are encouraged
to emphasize their own unique contributions and to raise constructive ques-
tions concerning procedures or suggestions and actions of other group members.
Risk-taking is also encouraged, as is creativity. These factors may be less
important during routine activity for tank crews, but they may be crucial
during the transition phase and periods of high stress.
The significance of cohesion, described above, arises in the context of
team-building activities since teams may become isolated and more oriented
to the enhancement of group performance, at the expense of other teams or
units. For tank crew teams this is essential because of the interunit commu-
nication and coordination required for successful maneuvers. Positive in-
tergroup relations and corporate role clarity are critical for this reason. The
former refers to the nature of the working relations with other teams or
units, the latter to a clear picture of the way in which each team fits into a
larger whole. Training could enhance both of these factors through simula
4
WORKLOAD TRANSITION
lion exercises and team-building strategies that increase cohesion without
increasing intergroup competition. Often intergroup competition is used to
enhance group cohesion, which would be counterproductive for the situa-
tion in which intergroup cooperation is required, as in the transition phase
and during subsequent maneuvers.
However, to the extent that team building is useful to improve perfor-
mance, raise levels of trust and commitment, and reduce stress that results
from external factors as well as internal factors such as poor integration,
lack of goal clarity, low levels of participation, and commitment, then strong
leadership is required to counteract the stress created by a more open cli-
mate involving more feedback and open management of conflict. Thus, we
return to the importance of leadership.
Good team qualities provide a buffer against stress, organizational as
well as environmental. Trust, participation in decision making relevant to
the work being performed, excellent communications, and a commitment to
collaboration have all been identified as conducive to effective team-build-
ing processes (Numerof, 1987; Tannenbaum et al., 1992~. Organizational
resistance to effective team building comes from two sources, perceived
threat and resistance to change. While some of these characteristics are not
particularly relevant to the tank crew environment, other features are of
central importance given that tank crews fit the above definition of a team
(i.e., a group that requires coordination and cooperation to produce an out-
come that no individual alone can produce).
Various organizational effects resulting from the failure to implement
good team-building strategies for both group and organizational-level out-
comes have also been identified (Numerof, 1987~. For example, suboptimization
occurs when organizational objectives are not clearly communicated. Indi-
viduals may perform their own functions appropriately, but coordination is
lacking. Organizational objectives may not be clearly defined or may change
often and thus result in greater stress and uncertainty. If there is low
commitment to the group and/or the organization and low cohesion, stress
in the group will be high and team performance will be impaired. In orga-
nizations in which work is characterized by high levels of interdependence,
frequent problem-solving efforts, and high demands for accuracy and/or
timeliness, team building is very important (Numerof, 1987~. For tank
crews and, similarly, air crews, this model has implications for selection,
recruitment, training, and the organization of roles and work assignments.
In addition to environmental buffers (e.g., alterations in the actual tank
environment), team-building efforts can be employed to minimize commu-
nication problems and the stress-related inefficiencies in decision-making
and problem-solving tasks, described in later chapters.
STRESS
115
SUMMARY
It is clear that considerably less is known about stress effects, and the
appropriate techniques for their remediation, than about many other aspects
of performance. This shortcoming results in part because of the great diffi-
culty in conducting research in the area-i.e., imposing realistic, credible
stressors in a controlled setting in a way that is also consistent with the
ethics of research. Still, enough data are available from incident reports,
from the research described above, and from the extensive reviews provided
by Broadbent (1971) and Hockey (1986) to construct a reasonably coherent
picture of those effects and suggest some possible remediations, as we have
done.
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