Download Stress and Design: Lessons Learned

Stress, Anxiety and the Interface: What Must Be Considered When
Designing for High-Risk Environments
Wendy J. Vestevich
HCI 450
Research Review
June 3, 2003
Technological advances have provided humans with unprecedented efficiency and
satisfaction in our daily lives. As it is widely known that humans are often the ones who
cause an error when dealing with a system particularly with completing menial tasks, it is
only logical that systems are implemented in environments where human error could mean
life or death. From airplanes to medical technology, it is paramount that users are able to
properly operate these systems under extremely stressful circumstances. This constitutes a
very important field of study for HCI specialists as this type of “extreme” research can carry
over to non-critical interface design, thus reducing human/system error rate. Even with the
advent of the in-dashboard navigation interface in automobiles, this type of research is
applicable; users (drivers) can be in a moment of anxiety due to poor visibility, they might be
lost, or there is simply too much noise in the vehicle when trying to decipher their proper
route. As HCI specialists, it is of utmost importance to consider the role of stress when
designing an interaction, and how the user physically responds to his/her environment when
trying to complete a task. The study of high-risk/critical systems is an excellent starting
point and can provide a solid foundation for all interaction design.
The Human Body Under Stress
Typically known as the “fight or flight” response, almost everyone has experienced a
visceral reaction to his/her environment, specifically defined, “a stressful situation is one
that is regarded as threatening and possibly exceeding his/her resources” (R. Lazarus, 1977).
Once a person realizes imminent danger, a hormonal change occurs in the brain as it
interprets the threatening situation by releasing increased amounts of the hormones
epinephrine and cortisol. These hormones prepare the body for quick, strenuous action, yet
are also responsible for impairment of memory formation and higher cognitive abilities (G.
Schelling, 2002). Psychologist Hans Selye outlined three common stages of the human
response to acute stress:
1. Alarm: Indicates a high arousal of the sympathetic nervous system which readies the
body for vigorous activity;
2. Resistance: A stage of prolonged arousal in which epinephrine levels remain high;
3. Exhaustion: Cortisol takes over as the dominant hormone and shifts energy to
increased blood sugar levels and increased metabolism and away from the body’s
immune system.
During the Alarm and Resistance phases, hormonal activity affects the frontal lobe of the
brain, the primary area where short-term memory and concentration abilities are held.
People under acute stress are also known to have problems with rational thought processes
and cannot effectively complete complex intellectual tasks. Fluids are diverted from the
mouth making it difficult to swallow and speak. Blood moves away from the skin to protect
and arm critical organs and muscles with energy for the fight or flight response, thus hands
become cold and often clammy. (Well-Connected Health Journal, 2002).
These unavoidable responses by the user should be used as benchmarks for
interaction design. Because the short-term memory function is impaired, there should be
reliance upon immediate recognition versus recall. Impaired speaking ability would hinder
the effectiveness of any voice-activated commands that are necessary to avoid disaster.
Stammering or stuttering would impede the computer from understanding the user. Touch
screens should be used for non-critical systems; there may be a malfunction or error if the
user’s clammy and trembling hand slips into the wrong area of the screen, or the screen may
not even respond to the user’s cold touch. With this being said, it is of note that “mission
critical” systems for the airplane cockpit strive to strike a balance between sensory overload
in a crisis, and allowing the system to steer the user through necessary processes in order to
avert disaster.
Stress and Design
One of the many challenges of cockpit design is to recognize that the user’s balance,
orientation and situational awareness may be compromised due to rapid altitude changes or
other environmental anomalies. In an analysis written this year, R.M.Boers defines two of
the greatest threats to pilots are “Spatial Disorientation (SD)” and “Loss of Situational
Awareness (LSA) [which] refer to the erroneous sense of position, heading and speed of the
aircraft relative to the earth’s surface [and the incorrect determination] of environmental
aspects like geographical position and military threats” respectively. Solutions to these
problems are not simply to automate everything, but to make sure the pilot does not ignore
warnings and other display alarms due to sensory overload or the “cocktail party effect”, all
while dealing with the physical demands of motion, gravitational force and oxygen depletion.
When the pilot is suffering from SD, he/she cannot interpret the context of these warnings.
Therefore cockpit design relies very heavily on what is called Information Theory, which
defines information as the reduction of uncertainty (R.M.Boers, 2003). As much
information as possible must be made available to the pilot for decision making under
physical and mental duress, and research into other methods of notification is being made
into cues other than visual, such as 3-Dimensional, Heads-Up Display and Auditory
Presentation.
The first, 3-D, is more applicable in a non-emergency situation to avert the problem
of Spatial Disorientation, however it has proven to be erroneous in emergencies not due to
pilot error but more to the machine misinterpreting and presenting information incorrectly
to the operator. Thus, this type of control has been deemed less-preferable by engineers
(R.M. Boers, 2003). Secondly, Heads-Up Displays utilize the existing visual focus of the
pilot (which is generally forward) and alleviates the problem of locating pertinent
information outside of the field of view (on the console, or “heads down” display). HeadsUp must be used sparingly so that other cues are not missed or ignored by the pilot. A
negative aspect of Heads-Up is the theory of “dark focus” in which the pilot is focused on
an area within the Heads Up and not the target outside of the airplane and this could
contribute to Spatial Disorientation and confusion especially engaged in a military operation.
However, this “dark focus” not a widely accepted principle (RM Boers), and pilots have
reacted and worked with this type of display favorably; thus Heads-Up is now being
incorporated into general and commercial aviation. Lastly, auditory cues are thought to
alleviate the copious amount of visual information in a cockpit, however, “the use of sounds
in a display is more fit to represent events in time, not so much events in space…[which] can
be overcome by developments in Virtual Reality that make it possible to generate spatialized
sound, so that it seems to originate from a certain place in the three-dimensional
environment” (Sanders & McCormick, R.M.Boers). Auditory cues are widely known to be
the most useful only in the direst of situations where immediate attention is required,
however since the pilot uses auditory communication with the ground and other aircraft, it is
important to make sure there is no occurrence of “crosstalk”. In a 1996 study (RM Boers), it
was determined that F-15 pilots highly rated a newly developed “situational awareness
enhanced” cockpit that incorporated some of the virtual technology previously discussed.
This is encouraging that designers are striking the important balance that can assist pilots
rather than hinder them with abundant technology.
Since cockpits are designed for expert users who expect emergency situations, then
what about a non-expert user forced to use a life-saving device correctly and quickly? The
case of the portable defibrillator is an excellent example of how simplification of the manmachine interface is extremely important. In an interview with TechTV, Tom Kelley, CEO
of Ideo, discussed the importance of simple, effective design. One of their versions of the
portable defibrillator was a “clamshell” design, similar to a laptop computer. “It wasn’t
obvious [enough] to them [users]”, demonstrating how Ideo designers thought the design
was totally logical, however testing proved otherwise. “We’re in a situation where seconds
make the difference between life and death. If it takes and extra 10 seconds to open the
latch, that’s a terrible design”.
Another firm, Global Techno Scan, developed the same device named the
ForeRunner. The initial factors these designers had to consider is that in the past,
defibrillators were used by cardiologists and trained medical personnel who could operate
the equipment in an expert manner, and more importantly, determine if the victim is in fact
suffering from cardiac arrest before administering the life-saving shock. Global Techno
Scan identified this as its main design goal, “The device must communicate immediately
what it is, exactly what to do, and help users do it quickly, confidently, and accurately in
socially and emotionally charged circumstances” (globaltechnoscan.com). Ideo recognized
this early on when an actual event in a subway station required the use of their (now newly
designed) defibrillator. A paramedic correctly set up the “brick” format (in which the
machine was shaped like a solid rectangle with a “simple” 1-2-3 step process for charging
and firing the shock), however lost control under this stress, obviously overwhelmed and
unable to handle the intellectual task at hand, and did not know where to push the button.
Kelley recounts: “an off-duty firefighter who had never seen the device before he came up,
looked over the person’s shoulder…pushed the orange button, delivered the shock, and
saved this guy’s life”.
Due to the chaotic situation the operator is dealing with, the
defibrillator cannot rely on the operator’s judgment to assess whether or not the patient is
suffering from cardiac arrest. The ForeRunner has a built-in redundant safety feature that
obtains information from the electrodes placed on the victim’s chest; if the information
from the chest to the electrodes to the machine indicates cardiac arrest, the shock is fired. If
the information is not consistent with cardiac arrest, the machine will not administer the
shock, protecting the bystanders and the victim from unnecessary shock. In their latest
design, the use of audible instructions has proven to be very effective in guiding the operator
through necessary steps. They chose to actually record the voice of Peter Thomas, the
British narrator of the television series Nova, who is known for his calming voice
(globaltechnoscan.com, 2001).
Stress and Design: Lessons Learned
A study done in 1994 indicates that the general rate of human error under high stress
levels is around 30% (Shelton, 1999). However, the human is unique in that the brain is
faster at adapting to rapid change and can recover quickly from anxiety-ridden situations.
Clearly from this study, it is true that auditory instructions can be extremely effective in both
expert and novice user environments, and the best design is the most simplistic under these
circumstances.
Despite his promotion of aesthetics and their positive effect on interface design,
Donald Norman has acknowledged the following: “Designs intended for stressful situations
have to particularly account for matching the needs of the users, for making appropriate
actions salient and easy to apply. In other words, the principles of good human-centered
design are especially important in stressful situations.” As mentioned earlier, interfaces not
typically seen as mission-critical such as automobile navigation systems will truly benefit
from the results of these studies. Clearly, the development of virtual reality and threedimensional displays will play a critical role in the future; however there still exists a huge
need for researching this type of technology’s effect on the user, specifically how the brain
with stress as interference will interpret this new display and will it successfully see the user
through to a safe ending. Thus, if HCI designers adhere to the lessons learned from this and
other mission-critical interface research, designs will be more intuitive, logical and easier to
use.
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Introduction to Psychology; Kalat, James W.; Wadsworth Publishing Company, 5th Edition,
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Mission-Critical Environments; 2003; Computer Science Department, University of California
Los Angeles: date accessed 5/25/03
http://www.cs.ucla.edu/hcip/Research/research.html
Norman, Donald; Emotion & Design: attractive things work better; Interactions, Volume 9,
Number 4 (2002)
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