ruud_hortensius Researcher_In_Social_and_Affective_Neuroscience

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The Bystander Effect

A classical finding in social psychology tells us that helping behavior during an emergency is reduced in the presence of others (‘the bystander effect’). In this line of research, we take a novel approach and investigate the neural mechanisms underlying bystander apathy, the influence of personality characteristics, and use behavioral measures to predict helping behavior during a violent conflict. Based on the outcome of these studies we have begun to formulate a theoretical model that describes helping behavior in bystander situations as the net effect of two competing motivational processes.


Hortensius R. & de Gelder B. (2018). From empathy to apathy: The bystander effect revisited. Current Directions in Psychological Science, 27:249 –256. [pdf]

Hortensius R., Neyret S., Slater M. & de Gelder B. (2018). The relation between bystanders' behavioral reactivity to distress and later helping behavior during a violent conflict in virtual reality. PLoS ONE, 3: e0196074. [pdf] [data]

Hortensius R., Schutter D.J.L.G. & de Gelder B. (2016). Personal distress and the influence of bystanders on responding to an emergency. Cognitive, Affective, and Behavioral Neuroscience, 16:672–688. [pdf]

Hortensius R. & de Gelder B. (2014). The neural basis of the bystander effect - The influence of group size on neural activity when witnessing an emergency, NeuroImage, 93: 53-58. [pdf]

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Last update: September 12 2018 (publications)


*A popularity contest in the robotic petting zoo will be part of the British Science Festival on September 14! Together with artist-in-residency Merel Bekking, we created an interactive public art performance. In this robotic petting zoo, a small group of vacuuming robots, all with unique characters, competed in a popularity contest. So much fun! Please check this page, the website or this BBC piece for more information.

*Our review paper on the attribution of socialness to artificial agents has been published in the Annals of the New York Academy of Sciences as part of the Year in Cognitive Neuroscience issue. In this review we discuss how the cognitive reconstruction within the human observer shapes human-robot interaction at the brain and behavioural level. Read the the article here.

*A review on the perception of emotion in artificial agents is in press in IEEE Transactions on Cognitive and Developmental Systems. In the review we integrate recent findings from social robotics, virtual reality, psychology, and neuroscience to examine how people recognize and respond to emotions displayed by robotic and virtual agents, and provide guiding principles for future development and research. Read the PsychArXiv pre-print here, the accepted version here or see the poster for the CERE conference here.

*Why do we fail to help during an emergency in the presence of other people? Together, with Beatrice de Gelder I propose a new theoretical perspective on bystander apathy that integrates emotional, motivational and dispositional aspects. Out now in Current Directions in Psychological Science.

---Coming soon---

*A preprint entitled: “Socialising with a robot and the flexibility of empathy”.