“…Despite previous claims (Warneken & Tomasello, 2013b), evidence cumulates that cooperation levels drop when anonymity is clearly implemented (e.g. in adults: Haley & Fessler, 2005;Hoffman, McCabe, Shachat & Smith, 1994;Franzen & Pointner, 2012;in children: Engelmann et al, 2012in children: Engelmann et al, , 2013Leimgruber et al, 2012;Piazza et al, 2011;, or in more natural set-ups (e.g. Winking & Mizer, 2013;Xiao & Houser, 2005).…”