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). Heads-Up 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 man-machine 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 three-dimensional 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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