Now, University of Otago psychology researchers are running experiments to find out if dogs really can detect human emotional messages.
Over the past 15 months, Associate Prof Ted Ruffman and a team of students have put 90 Dunedin dogs, of all shapes sizes and breeds, through their paces.
Some have been shown recorded images of babies laughing, crying and babbling, while others have been given a specific verbal instruction from humans displaying either happy or stern expressions.
The dogs' responses indicated they could indeed differentiate a happy human from an angry or sad one and a laugh from a cry, Prof Ruffman said.
"We know dogs are very good at picking up on human gestures ... and it seems they are very good at picking up on human emotions, too."
The dogs who watched the crying baby responded differently to those who saw the laughing or babbling child, he said.
They strained to get behind the television screen to "find" the baby, cocked their heads, and showed signs of concern.
Prof Ruffman said it was known humans had a strong physiological response to a baby crying in distress and it seemed dogs had a similar response.
The studies were designed to try to find out whether dogs had a natural empathetic response to human emotion, or whether their reactions were based on the positive reinforcements they received from humans as a result.
"If dogs do show natural concern, it would explain a lot about why they are treated as caring members of the family."
The research team was seeking more dogs to carry out further studies, he said.
One proposed experiment was whether dogs would react in different ways to humans giving non-verbal expressions of emotions such as happiness or fear.
Another, which still required ethical approval, would look for the presence of the stress hormone cortisol in dog saliva.
Anyone wishing to participate in the study can contact Prof Ruffman at tedr@psy.otago.ac.nz
