As anyone with a dog will tell you, there's a good chance they'll perk up if they see you've got food on you or some sort of treat for them.
However, a new study by the University of Portsmouth's Dog Cognition Centre - which tries to map and understand dog behaviour in a scientific capacity - has found that dogs respond to humans no matter what they have. In fact, the study found that dogs are more emotive and responsive when a human is looking at them.
Dr. Juliane Kaminski explained that "(we) can now be confident that the production of facial expressions made by dogs are dependent on the attention state of their audience and are not just a result of dogs being excited. In our study they produced far more expressions when someone was watching, but seeing food treats did not have the same effect."
"We knew domestic dogs paid attention to how attentive a human is - in a previous study we found, for example, that dogs stole food more often when the human's eyes were closed or they had their back turned. In another study, we found dogs follow the gaze of a human if the human first establishes eye contact with the dog, so the dog knows the gaze-shift is directed at them."
According to the research from the study, dogs commonly used the so-called 'puppy-dog' look - however, the study was not able to specify whether dogs used this when they were sad or merely to elicit a response from humans.