Eye scan patterns in a simulated ambulance dispatcher´s task.

Abstract

A simulated ambulance dispatch task was used to study the effects of mental workload on eye scan patterns. Participants received an extensive training to be able to perform well on every part of the ambulance dispatch task. During the experiment participants had to complete a scenario that consisted of six 15-minute periods; periods with low mental demand were followed by high workload demand periods and vice versa. Eye movements were recorded to compute fixation times, dwell times and entropy (a measure for randomness in eye scan patterns). These measures were calculated in five areas of interest. Results show that task performance was faster during high workload periods, while dwell times were shorter in these periods compared to lower workload periods. Entropy showed a more complex pattern of results. For time segments in which participants were involved in ambulance planning for ordered patient transport (A3 rides) entropy was lower in high workload periods, indicating a more systematic pattern of activities. However, for time segments in which the main task was selection of ambulances for emergency rides entropy was higher in high workload periods. It was concluded that participants use different task strategies in periods of high mental workload. Furthermore, it proved to be possible to detect these strategy changes by means of scan pattern analysis.