Authorities will question Facebook over an experiment in which the social network secretly manipulated the feelings of users to test their mood, officials said Wednesday. Facebook tampered with the system used to create news feeds for 700,000 users to test emotional contagion for one week in 2012 without their knowledge. Were aware of this issue and will be speaking to Facebook, as well as liaising with the Irish data protection authority, to learn more about the circumstances, a spokesman told AFP. Facebooks European headquarters are based in the Irish capital Dublin, meaning EU laws, not US ones, apply to its operations.