Are face recognition abilities in humans and sheep really 'comparable'?

Knolle et al. [1] tested the ability of sheep to recognize human faces. Their results provide a compelling demonstration of advanced human-face recognition abilities in sheep, and make an important contribution to work seeking to understand the visual, cognitive and neural processes driving face and object recognition in non-human animals. However, as scientists who study face recognition in humans, we believe Knolle et al.'s claim that ‘sheep have advanced face-recognition abilities, comparable with those of humans' (abstract, page 1) is unwarranted given their data.