Dogs have been domesticated by humans some 15,000 years and every pet owner from then to now can convey some story of their canine offering them some sort of understanding and comfort in times of sadness.
Research has shown us that dogs are master communicators but it hasn't shown us that they can demonstrate empathy or truly understand our pain. In one study in 2006, dog owners were instructed to fake heart attacks and their pets failed (unlike Lassie) to go fetch help. But there are tales of dogs doing exactly the opposite of what this research states. Perhaps dogs are, indeed, master communicators and they can differentiate between an actual and fake heart attack? Perhaps.
A Response to Tears
Various studies have suggested dogs do, however, respond uniquely to tears. An online study published in the journal 'Animal Cognition' at The University of London have discovered that dogs were most likely to approach a crying person more so than someone who is humming or talking and they also responded with submissive behavior to a person weeping. This is how you would expect a dog to react if they understood our pain (but again, researchers state this is not proof that they do.) What the dogs did do was differentiate between the crying and the humming which shows us they weren't driven purely by curiosity but by some other stronger overall response.
Which brings us to another question: Can Dogs Cry Tears of Sadness? I can't speak from experience here because our dog actually has a dry eye problem we have to treat with an eye ointment which lubricates his eyes and supplies him with tears. Other dogs actually may shed a few tears but it's not from emotions as we know them. Yes, dogs are sympathetic creatures who share our joys and sorrows but emotional crying is usually an action associated with humans. This is not to say dogs do not experience emotions because they have been known to grieve in their own way, just not necessarily by shedding tears. When your dog becomes upset you may notice some watery eyes resulting from their particular situation. When they don't want you to leave or they're not getting their doggy treat or someone steps on a paw or a tail - all these instances are traumatic for a dog and may bring about whining and tears.
Other Causes For Doggie Tears
Allergies are the one big cause of a dogs watery eyes. Each blink of your dog's eyes produce tears that will run down your dog's face if your dog has blocked tear ducts. This definitely looks like crying! An infection or something irritating your dog's eyes may also do the same. If your dog's eyes are constantly watering you best make that vet appointment for a checkup, especially if their eyes are secreting more than clear tears. If the discharge is yellow, mucous or bloody, something is wrong and must be treated. Researchers have also shown us that dogs have neural pathways much like those of a human and they can experience physical pain in much the same manner as do we. Some dogs even have an IQ comparable to that of a 3 year old human! So with all this going for them, I'm simply not convinced that dogs don't experience emotional responses such as jealousy, grief and sometimes even tears of pain and joy!