Indicadores antropométricos

One way to explore if simulated driving can provide a more realistic test of driving skills is through the recording of physiological measures. The fundamental assumption of using physiological measurements is that all aspects of human behavior evoke physiological reactions, with these physiological reactions being involuntary and uncontrollable (Bouscein & Backs, 2008). As a result, physiological recordings can provide a valid representation of a person’s mental state, which in turn provides a means for studying the underlying cognition processes of various behaviors (including driving). Physiological measures are often recorded to assess the level of arousal of an individual. The level of arousal is measured along a continuum, ranging from low to high. For example, low arousal would be present during sleep while high levels of arousal would be present during physical exertion. Arousal operates via the sympathetic autonomic nervous system and takes the form of a variety of physiological reactions including an elevated heart rate, increased respiration rate, increased skin conductance (electrodermal dermal response) and pupil dilation. Arousal can also vary due to emotional reasons, for example as a result of stress. Importantly, arousal is also affected by cognitive changes, such as mental workload. As a result of this, physiological recordings can provide a measure of cognitive factors during tasks such as driving.

Two commonly used measures of physiological changes are heart rate and skin conductance. Heart rate is the speed at which the heart beats, usually measured in the number of beats per minute (bpm), as well as in terms of the change in heart rate and the variability of the heart rate. Changes in heart rate can be caused by factors such as exercise, stress and anxiety. As a result of this, heart rate can be used as a measure physical and psychological arousal. Skin conductance is a method of measuring the electrical conductance of the skin, which varies depending on the state of the sweat glands. Much like heart rate, sweating is controlled by the sympathetic nervous system; meaning that skin

conductance is used as a measure of physiological and psychological arousal. When the sympathetic autonomic nervous system is aroused, the activity of the sweat glands increases, which in turn increases skin conductance. Skin conductance can be measured in terms of its mean, total or in terms of the number of specific electrodermal responses (EDRs) recorded over a period of time.

Research has revealed that physical and mental workload impact heart rate (de Waard and Brookhuis, 1991) as well as skin conductance (Boucsein, 1992). Mehler, Reimer and Coughlin (2012) found that skin conductance increased with increasing task demands, meaning that skin conductance can be used for discriminating between different task difficulties. As a result, these physiological measures can be used to measure changes in mental workload during psychological tasks.

Research has revealed that heart rate increases during effortful working periods of simulated work such as driving (Dijksterhuis, Brookhuis, and De Waard, 2011)  and flying (De Rivecourt et al., 2008), real life work such as on-road driving (de Waard and Brookhuis, 1991) and during laboratory tasks such as working memory task (Backs and Seljos, 1994). Brookhuis and de Waard (2011) have advocated the use of physiological measures in combination with driving simulators. If driving in a simulator can provide similar physiological responses to on-road driving and more representative physiological responses than those observed using a video-based tasks, this could indicate the validity of simulator driving for testing driving abilities. A number of studies have explored the physiology of driving, measuring variables such as heart rate and skin conductance.

Dijksterhuis, Brookhuis, and De Waard (2011) recorded the physiology of drivers as they participated in a simulated driving study investigating steering and lane keeping. Participants drove in a driving simulator, while the width of the road and the density of oncoming traffic was manipulated. Compared to baseline, driving in the simulator resulted in an increase in heart rate. Meanwhile an increase in the amount of incoming traffic resulted in a decrease in heart rate variability. The authors attributed these changes in heart rate to increased mental workload during the simulated driving.

Skin conductance has also been reported to be sensitive to levels of arousal and workload during driving (Healey and Picard, 2005). Taylor (1964) recorded

skin conductance while people drove on the road. The results of the study revealed that skin conductance was negatively correlated with driving speed. He observed that in high-risk situations (when skin conductance levels were high) participants slowed down, whereas in low-risk situations (when skin conductance levels were low) participants drove faster. These were taken to support the idea of risk homeostasis is utilised in driving. Risk homeostasis (Wilde, 1994) is the idea that people attempt to find a balance between their subjective perception of risk and the amount of risk they perceive is acceptable. With regards to driving, this means that drivers will adjust their driving behaviour to balance out any perceived risk. For example, if a driver perceives the level of risk to be lower than what they deem acceptable then they will engage in a behaviour that increases the perceived level of risk (e.g. speeding up). Meanwhile, if a driver perceives the level of risk to be too high they will engage in a behavior that will reduce their level of perceived risk (e.g. slowing down). The fact that perceived risk can result in anxiety allows for measurement via skin conductance.