Furthermore, we examined the influence of severe time pressure on the decision-making process. Our model comparison shows that simple models based on one-dimensional value-of-life scales are suited to describe human ethical behavior in these situations.

We randomly sampled obstacles from a variety of inanimate objects, animals and humans. In the study, participants controlled a virtual car and had to choose which of two given obstacles they would sacrifice in order to spare the other.

We employed immersive virtual reality to assess ethical behavior in simulated road traffic scenarios, and used the collected data to train and evaluate a range of decision models. Models of ethics for self-driving cars should thus aim to match human decisions made in the same context. Previous research has shown that moral judgment and behavior are highly context-dependent, and comprehensive and nuanced models of the underlying cognitive processes are out of reach to date. The same algorithms are also likely to be used in millions of cars at a time, increasing the impact of any inherent biases, and increasing the importance of getting it right. Ad hoc decisions are made in milliseconds, but can be based on extensive research and debates. By using algorithms to make decisions in situations where harming humans is possible, probable, or even unavoidable, a self-driving car's ethical behavior comes pre-defined. Self-driving cars are posing a new challenge to our ethics. Neuroinformatics, Institute of Cognitive Science, Osnabrück University, Osnabrück, Germany.Sütfeld *, Richard Gast, Peter König and Gordon Pipa

Ethical decisions