Because dogs can’t speak, scientists have relied on behavioral observations to infer what dogs are thinking. It is a tricky business. You can’t ask a dog why he does something. And you certainly can’t ask him how he feels. The prospect of ferreting out animal emotions scares many scientists. After all, animal research is big business. It has been easy to sidestep the difficult questions about animal sentience and emotions because they have been unanswerable.

Until now.