The study was relatively small, involving only 34 dogs and their owners, and of course there is no way to determine exactly what the dogs were thinking or what their motives were.

Yet the findings could help pave the way for better evaluating what influences canines, especially service dogs, to help their human companions in times of need.

“It’s really cool for us to know that dogs are so sensitive to human emotional states,” said Emily Sanford, a graduate student in psychological and brain sciences at Johns Hopkins University who was a co-author of the study.