There’s a good chance you looked at this picture of a couple on holiday, brilliantly photo-bombed by a squirrel, and it made you smile. You wouldn’t be alone. Why? Because this photo came top in a new poll to find the happiest photograph, with 71% of people unable to resist smiling at it.

Taken in 2009, while the couple were on holiday in Canada, the photograph topped a list of photos identified for being able to provoke an instant happy response. The squirrel saw off stiff competition from photographs of beautiful landscapes, silly human antics, babies, dogs, cats and over 10 other types of animal, including social media sensation and ‘world’s happiest animal’ – the quokka.

"The findings suggest that it’s often small things - like a cute animal or unexpected photo-bomb - that make us feel happy" said Bobby Brittain, Marketing Director, Coca-Cola Great Britain. "Our Choose Happiness campaign is all about inspiring people to appreciate the little things that raise a smile. That's why we’re encouraging people to capture whatever makes them happy this summer and giving away up to one million selfie sticks.”

Coca-Cola worked with renowned picture agency Getty Images on the research. Asked to click on photographs that made them smile, people were found to be more likely to smile at an image of a cat than a dog, while images featuring babies made less people smile than those featuring animals.

Infographic: Why is the squirrel shot so successful at evoking a happy response?

The image is layered with at least five psychological factors that have been proven to have a positive effect on the viewer.

Psychologist Dr Simon Moore explains,“The unexpected element in this shot, and our response to it, may help to explain why photo-bombing has become such a popular trend – it results in an unexpected emotional experience. Sudden ‘nice’ surprises are good as psychologically we feel we got more than we were expecting.”

So what are the top tips for taking ‘happy snaps’? Dr Moore advises: “The results of this poll suggest that the key ingredients for capturing pictures that make people smile are actually very simple. Start with a cute – preferably baby – animal, add a beautiful, natural backdrop, a grin or two, and a (nice) surprise and you won’t go too far wrong.”

“The research results are fascinating as they suggest we are very influenced by our instincts and that deep-rooted systems still play a significant role in how we react emotionally to things around us. It makes me smile as a psychologist to think that whoever you are, for a fleeting moment, a cheeky squirrel can make so many of us respond in the same way.”