Fig. 1

Hypotheses tested. A Phylogeny of the species played back [28]. B Examples of sounds produced in emotionally loaded negative and positive situations for each species, which were used in the playbacks (above, oscillogram; below, spectrogram). C Hypotheses tested in this study (non-exclusive): familiarity (all species recognize human emotions, as they are all exposed to human caretakers on a daily basis, while they should not recognize the emotions of the closely related species that they have never heard); phylogeny (closely related species recognize each other’s emotions better, or at least as well as human emotions); domestication (domestic species recognize human emotions, but wild ones do not)