What would it be like to measure and publicize the emotions of a city’s dwellers? Would we like what we saw? Would it benefit us? Or in an era of data deluge, are there some things that are simply better left unknown? Well, that really depends on whom you ask. This question was the philosophical heart of an art installation that made a splash a few years ago when it was first installed in Berlin, and later in Lindau, a small town in southern Germany.