Since the outbreak of the pandemic, there has been a great longing for other people. Most of all, many lack the closeness to relatives, friends or colleagues. But the virus also endangers another type of relationship: fleeting encounters with more or less strangers, in front of the kiosk, while shopping, when walking the dog or in a café. Social scientists consider such loose contacts to be irreplaceable - especially now: "Whether you drink coffee alone at home or at the table in a café, surrounded by scraps of conversation, cannot be compared at all," says Maxime Felder from the Swiss Federal Institute of Technology in Lausanne. But why is that exactly?