WHEN man’s best friends pull puppy-dog eyes at their owners they’re undoubtedly after an extra treat, walk or a bit of affection.
Now researchers at the University of Portsmouth have revealed that dogs have developed specific muscles around their eyes in a bid to try and melt hearts.
Experts have found dogs have a small muscle which allows them to raise their inner eyebrow, triggering a nurturing response in humans. The movement makes the dog’s eyes appear larger, more infant like, and imitates humans when they are sad.
The research team, led by comparative psychologist Dr Juliane Kaminski, at the University of Portsmouth, included a team of behavioural and anatomical experts in the UK and USA.
Dr Kaminski said the strong desire to look after your tail-wagger is achieved by the result of this simple muscle movement and gives dogs a selection advantage over others.
‘The evidence is compelling that dogs developed a muscle to raise the inner eyebrow after they were domesticated from wolves,’ Dr Kaminski said.
‘We also studied dogs’ and wolves’ behaviour, and when exposed to a human for two minutes, dogs raised their inner eyebrows more and at higher intensities than wolves.
‘The findings suggest that expressive eyebrows in dogs may be a result of humans unconscious preferences that influenced selection during domestication.
‘When dogs make the movement, it seems to elicit a strong desire in humans to look after them. This would give dogs, that move their eyebrows more, a selection advantage over others and reinforce the ‘puppy-dog eyes’ trait for future generations.’
The expression has such a powerful effect on humans, yet the muscles that control the eyebrow movement are so thin you can see through them.
Co-author and anatomist Adam Hartstone-Rose, at North Carolina State University, USA, said it was ‘remarkable’ that the social interaction has led to such a quick change in evolution.
The only dog species in the study that did not have the muscle was the Siberian husky, which is among more ancient dog breeds.
An alternative reason for the human-dog bond could be that humans have a preference for other individuals which have whites in the eye and that intense eyebrow movements expose the white part of the dog’s eyes.