Abstract
The usefulness of cardiovascular measures as indicators of changes in cognitive workload has been addressed in several studies. In this paper the question is explored whether cardiovascular patterns in heart rate, blood pressure, baroreflex sensitivity and HRV that are found are consistent within and between two simulated working environments. Two studies, were performed, both with 21 participants: one in an ambulance dispatch simulation and one in a driving simulator. In the ambulance dispatcher task an initial strong increase in blood pressure is followed by a moderate on-going increase in blood pressure during the next hour of task performance. This pattern is accompanied by a strong increase in baroreflex sensitivity while heart rate decreases. In the driving simulator study, blood pressure initially increases but decreases almost to baseline level in the next hour. This pattern is accompanied by a decrease in baroreflex sensitivity, while heart rate decreases. Results of both studies are interpreted in terms of autonomic control (related to both sympathetic and para-sympathetic effects), using a simplified simulation of a baroreflex regulation model. Interpretation of the results leads to the conclusion that the cardiovascular response patterns in both tasks are a combination of an initial defensive reaction, in combination with compensatory blood pressure control. The level of compensatory blood pressure control, however, is quite different for the two tasks. This helps to understand the differences in response patterns between the two studies in this paper and may be helpful as well for understanding differences in cardiovascular response patterns in general. A substantial part of the effects observed during task performance are regulatory effects and are not always directly related to workload manipulations. Making this distinction may also contribute to the understanding of differences in cardiovascular response patterns during cognitive workload.
Highlights
Cardiovascular measures are extensively studied in both laboratory and applied environments to gain insight in either responsiveness or in operator state changes during continuing mental work
There is a decrease in heart rate (HR) during the first half of the session [F(1, 20) = 39.6, p < 0.001], while the level does not change in the second half of the session
The same relationship given by the model suggests that the lower heart rate during task performance is due to an increase in vagal gain, partly compensated by a decrease in sympathetic gain
Summary
Cardiovascular measures are extensively studied in both laboratory and applied environments to gain insight in either responsiveness or in operator state changes during continuing mental work. Cardiovascular measures are mentioned by different authors as good candidates for the assessment of operator state because they can be measured relatively and continuously (Hockey et al, 2003; Mulder et al, 2003, 2004) In several studies it has been shown how psychophysiological measures can be used in adaptive automation (Pope et al, 1995; Prinzel et al, 2000; Fairclough and Venables, 2006; Ting et al, 2010). Knowledge about a person’s current state, in combination with information about task load and task performance, can be applied to adapt the working environment to fit the user’s demands or needs (Haas and Hettinger, 2001). The basic idea of adaptive automation or adaptive support is to design a system that will give valuable help, being a companion for the operator during periods of expected over- or underload (Hoogeboom and Mulder, 2004), for example by controlling task demands
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