Their study, published in the Behavioural Processes, involved training a dozen dogs to remain motionless, while unsedated and unrestrained, in an MRI machine. A dog's sense of smell is 10,000 to 100,000 times greater than that of humans. Part of that is because the dog has 50 times more olfactory receptors than the human nose. A human nose has 6 million sensory receptors while a dog have 300 million sensory receptors or more. It is also attributable to the dog's brain. Proportionally, a dog's brain assigns 40 percent more space to analyzing smells than the human brain does. Researchers were able to observe the dog's olfactory bulb, which indicated the dog's sense of smell had been activated, and the caudate. Rich in dopamine receptors, the caudate sits between the brainstem and the cortex. In humans, the caudate plays a key role in the anticipation of things we enjoy, like food, love and money. Specific parts of the caudate stand out for their consistent activation to many things that humans enjoy. Caudate activation is so consistent that under the right circumstances, it can predict our preferences for food, music and even beauty. (6)
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MRI scan of dog's caudate lighting up when given a reward signal. |
This same brain system exists in dogs and researchers believe they use it to process pleasurable experiences, functioning just as the human caudate would. Smells were presented to the dogs from the dog itself; a different dog who resided in the same household; an unfamiliar dog; a familiar human; and a human the dog had never met. The olfactory bulb was activated similarly with each scent presented, but the smell of the familiar human activated the caudate region far more noticeably. Even if the familiar human was not the primary caregiver and the dog was not accustomed to receiving treats from this person. This is proof that dogs have the ability to experience positive emotions, like love and attachment, and would mean that dogs have a level of sentience comparable to that of a human child. It puts away old notions that animals, including dogs, are like robots and experience no emotions. Surprisingly, it was a view that was popular among scientists and researchers up until quite recently.
#3 Sight
When humans study a new face their eyes fall to the left, observing the right side of the face first. This is because the right side of the human face expresses emotions much more clearly than the left side. This "left gaze bias" only occurs when we encounter faces and does not apply any other time, such as when inspecting animals or inanimate objects. Researchers at the University of Lincoln have now shown that dogs also display "left gaze bias", but only when looking at human faces. No other animal has been known to display this behavior before. A team led by Dr Kun Guo showed 17 dogs images of human, dog and monkey faces as well as inanimate objects. Film of the dogs' eye and head movement revealed a strong left gaze bias when the animals were presented with human faces. But this did not occur when they were shown other images, including those of dogs. (7)
"Guo suggests that over thousands of generations of association with humans, dogs may have evolved the left gaze bias as a way to gauge our emotions," New Scientist magazine reported.
"Recent studies show that the right side of our faces can express emotions more accurately and more intensely than the left, including anger. If true, then it makes sense for dogs - and humans - to inspect the right hand side of a face first."
This proves that dogs understand that human emotion is displayed on the face and because it benefits them to respond accordingly, they have developed a way of detecting our moods. Betsy, the border collie with a vocabulary of 300 words, also showed an amazing ability to identify pictures of objects. Despite the images of toys being two-dimensional, Betsy showed no inability to connect the two-dimensional object to it's three dimensional counterpart. The owner held up a picture of a fuzzy, rainbow-colored Frisbee and urged Betsy to find it. Betsy studied the photograph and her owner's face, then ran into the kitchen, where the Frisbee was placed among three other toys and photographs of each toy. Betsy brought either the Frisbee or the photograph of the Frisbee to her owner every time.