1 Department of Biology, Unit of Ethology, University of Pisa, Via Volta 6, Pisa 56126, Italy. Electronic address: elisabetta.palagi@unipi.it.
2 Institute of Neuroscience, National Research Council of Italy (CNR), Via Volturno 39/E, Parma 43125, Italy. Electronic address: fausto.caruana@in.cnr.it.