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Automated vehicles promise to improve road safety and increase travelling comfort. Yet, recent accidents have raised awareness of the challenges posed by the way humans interact with such systems. Many of these challenges present a common denominator: user trust. While a lack of trust may induce drivers not to use the automated vehicle’s functionalities, excessive trust can lead to dangerous outcomes, with drivers using the system in situations it cannot cope with. Successful and safe interaction between humans and automated driving systems requires trust calibration: the process of continuously aligning driver trust to the reliability of the automated driving system. To date, there have been few studies focussing on the way driver trust varies from situation to situation, and the way in which experience in a range of situations may lead to more appropriate trust levels. Studies of driver trust also face a number of methodological issues including a lack of on-road investigations, concerns regarding the validity of simulator-based research, and the lack of reliable real-time measurements for the assessment of user trust. This dissertation partially addresses these research gaps. Our findings show that, before on-road experience, drivers tend to overestimate the capabilities of vehicles equipped with Level 2 systems. After experiencing the vehicles in multiple scenarios, drivers had a better understanding of vehicles’ limitations, resulting in better calibrated trust. Following studies were performed in simulated environments. Through a first validation study, we made sure that our driving simulator elicited in our participants a strong “sense of presence” - the feeling of truly belonging in the virtual environment. A second study showed that users’ trust levels in specific situations did not consistently match evaluations of vehicle reliability given by engineers. Finally, results obtained through a third study showed that combining gaze behaviour with electrodermal activity provided an effective measure of trust in a simulated automated vehicle. The real question is not whether “to trust or not to trust” automated driving technology. What we should be asking is when an automated vehicle can be trusted, and what can be done to calibrate user trust with the actual capabilities of the system.

In road-crossing situations involving negotiation with approaching vehicles, pedestrians need to take into account the behavior of the car before making a decision. To investigate the kind of information about the car that pedestrians seek, and the places where do they look for it, we conducted an eye-tracking study with 26 participants and analyzed the fixation behavior when interacting with a manually-driven vehicle that approached while slowing and displaying a yielding behavior. Results show that a clear pattern of gaze behavior exists for pedestrians in looking at a vehicle during road-crossing situations as a function of the vehicle’s distance. When the car is far away, pedestrians look at the environment or the road space ahead of the car. With the approach, the gaze gradually shifts to the windshield of the car. We conclude by discussing the implications of this insight in the user-centered-design of optimal external Human-Machine-Interfaces for automated vehicles.

A crucial factor influencing the validity of VR is sense of presence. The aim of this study is, firstly, to increase sense of presence of simulator driving by introducing an anxiety-inducing risk factor. Secondly, to add clarification to the partly inconclusive relationship between sense of presence, anxiety and physiological markers. The study consisted of two groups. The control group drove in the simulator normally. The threat group expected an electric shock in case of collision. Self-report ratings (on sense of presence, anxiety and task load), behavioral (speed, steering reversal rate, brake pedal use) and physiological measurements (EDA, HR) were taken. We expected an increase in the sense of presence, arousal, steering reversals, brake pedal use, task load and anxiety ratings, and a decrease of speed in the threat group. Analyses revealed partial group differences in speed and steering reversal rate. Sense of presence was identical and notably high in both groups. This implies that either a more aversive stimulus might be needed to induce anxiety and increase sense of presence, or that it can hardly be increased at all in highly immersive VR systems.

Adopting the perspective of another person is an important aspect of social cognition and has been shown to depend on multisensory signals from one’s own body. Recent work suggests that interoceptive signals not only contribute to own-body perception and self-consciousness, but also to empathy. Here we investigated if social cognition – in particular adopting the perspective of another person – can be altered by a systematic manipulation of interoceptive cues and further, if this effect depends on empathic ability. The own-body transformation task (OBT) – wherein participants are instructed to imagine taking the perspective and position of a virtual body presented on a computer screen – offers an effective way to measure reaction time differences linked to the mental effort of taking an other’s perspective. Here, we adapted the OBT with the flashing of a silhouette surrounding the virtual body, either synchronously or asynchronously with the timing of participants’ heartbeats. We evaluated the impact of this cardio-visual synchrony on reaction times and accuracy rates in the OBT. Empathy was assessed with the empathy quotient (EQ) questionnaire. Based on previous work using the cardio-visual paradigm, we predicted that synchronous (vs. asynchronous) cardio-visual stimulation would increase self-identification with the virtual body and facilitate participants’ ability to adopt the virtual body’s perspective, thereby enhancing performance on the task, particularly in participants with higher empathy scores. We report that participants with high empathy showed significantly better performance during the OBT task during synchronous versus asynchronous cardio-visual stimulation. Moreover, we found a significant positive correlation between empathic ability and the synchrony effect (the difference in reaction times between the asynchronous and synchronous conditions). We conclude that synchronous cardio-visual stimulation between the participant’s body and a virtual body during an OBT task makes it easier to adopt the virtual body’s perspective, presumably based on multisensory integration processes. However, this effect depended on empathic ability, suggesting that empathy, interoception and social perspective taking are inherently linked.