Why Do Dogs Shake?
An athlete is hit hard in a game and is momentarily stunned with pain. The coach says "shake it off;" which he does, literally, either by wriggling the affected body part or by shaking his head to clear the cobwebs. Likewise, when the play between two dogs gets a little too rough, first one dog, and then invariably the other, stop what they're doing and then shake themselves off just as if they were drying off after a swim. At first this behavior seems straightforward enough, when we sustain a minor injury the rapid movement of muscles gets warm blood flowing into the area while simultaneously distracting us from the pain, and of course, post-swim, a dog wants to be rid of the heavy sheet of water enveloping their body. But that's not the whole story either because dogs do this even when physical contact hasn't yet been made or after a tentative first sniff of their partner.
Consider conducting the following experiment (but only presuming you know your dog is okay with it). Approach your dog and give him a nice big wrap around bear hug, pressing your cheek close to his head, then disengage and standing quietly, observe his response. Especially when a dog is indoors and can't deflect himself by doing something else, many dogs will shake themselves off just as if they've received a bop on the nose or have pulled themselves out of the water. Why?
Because as a human being I know that there aren't enough hugs going round the world: were someone I love to give me an unsolicited act of random kindness in the form of a big warm hug, I would willingly return such an embrace. But then I guess that's just me being mental given that the human intellect can process context. However since dogs don't process love on the mental stage, as human beings are capable of doing, they tend to respond quite differently and so you will probably see your dog step away and then shake off the hug.
The clue to the significance of the shake-it-off reflex can be found in another oft-heard coaches' bromide, "walk-it-off."Emotion is energy-in-motion, which is why the more emotional we feel the more animated we become and want to move. And as energy emotion has an internal dynamic of movement that works quite like the tides in that there is a rising and an ebbing effect. When emotion sweeps over us, we can feel it surge as if we're a tidal basin being flooded with a wave, and then these effects slowly subside and in fact can linger for a very long time. So in the animal mind, when there is an input of love that falls outside this natural rhythm, the canine mind doesn't necessarily process it as love, but rather as social pressure, which to a dog is equivalent to pain and since the emotional circuitry piggybacks on the most basic systems of physiology, the dog shakes it off.
From the Psychology Today Blog of Michael J. Formica:
"A recently published study suggests that intense feelings of social rejection are experienced in much the same way as physical pain. The study showed that the regions of our brain activated by physical pain are similarly activated when we are confronted with an intense experience of social rejection."
"The findings show that powerfully inducing feelings of social rejection activate regions of the brain also involved in the sensation of physical pain, while those same brain regions are rarely activated in neuroimaging studies of emotion. Kross remarks that this is consistent with the idea that the experience of social rejection -- or, more generally speaking, social loss -- appears to represent a distinct emotional experience uniquely related to physical pain."
And the best way to deal with rejection? Do what dogs do, shake it off and keep on moving. So my advice to dog owners wondering how to show affection to their dogs if hugging and kissing can be construed by a dog as social pressure---is to do onto their dog what they would pay for a masseuse to do onto them. A good massage is performed quietly and with a deep, kneading action that is calming rather than stimulating. If the masseuse patted our heads, scratched our sides, hugged us head to head and chatted up a storm, I daresay there's goes the tip. So to give a dog love, nothing beats a good rub-a-dub given slowly and deeply and I don't know of any dog that will shake off that kind of act of random kindness.