The relationship between humans and dogs dates back as far as 100,000 years. A recent study has found the irresistible nature of dogs to be evolutionary, with ‘puppy dog eyes’ being an evolutionary advantage.
Dogs and wolves diverged 33,000 years ago providing dogs with a selection advantage. Therefore, ‘puppy dog eyes’ may be more of a survival strategy rather than an expression of friendship. Recent research has found that dogs raise their inner eyebrows with a higher intensity than wolves when in the presence of humans. This contributes to the expression of melancholy in dogs. The expression is like the expression which humans make when they are sad. The gaze between humans and dogs also resembles the gaze shared between mother and child and hence humans have a strong necessity to care and look after dogs.
Recent research has found that dogs raise their inner eyebrows with a higher intensity than wolves when in the presence of humans. This contributes to the expression of melancholy in dogs
Movement in the region of a muscle called Action Unit 101 is responsible for the caring expression in dogs which contributes to the human-dog bond. Additionally, a muscle in the forehead called the Levator Anguli Oculi Medialis (LAOM) also contributes to the raising of the inner eye muscles. Both result in a melancholy expression on dogs. The LAOM muscle has been found in Chihuahuas, Labradors, Bloodhounds, Siberian huskies and Mongrels. In wolves, however, this muscle is not present. The LAOM muscle is likely to be developed from a domestication process since dogs and wolves are related.
Researchers also studied whether the expression of dogs and wolves vary. 27 Staffordshire bull terriers in shelters across the UK were studied as well as 9 wolves in 2 different parks. The specialist recorded when the animals made the ‘puppy dog eyes’ expression and rated the intensity on a five-point scale. It was found that the frequency of the ‘puppy dog expression’ was more common in dogs rather than wolves. More strikingly it was found that despite dogs and wolves both producing ‘low intensity’ expressions, only dogs have evolved the ability to produce ‘high intensity’ expressions. Since ‘puppy dog eyes’ are an evolutionary advantage, this significant facial muscular change between dogs and wolves can be directly linked to dogs’ higher levels of social interaction with humans.
Movement in the region of muscle called Action Unit 101 is responsible for the caring expression in dogs which contributes to the human-dog bond. Additionally, a muscle in the forehead called the Levator Anguli Oculi Medialis (LAOM) also contributes to the raising of the inner eye muscles
Rescue dogs are more likely to find an owner if they raise their inner eyebrows according to Professor Bridget Waller, the director of the Centre for Comparative and Evolutionary Psychology at the University of Portsmouth. Additionally, Waller found that puppy dog eyes were more effective than tail wagging or the speed at which dogs approach humans to show affection.
Overall, dogs are able to generate specific facial expressions which serve as an evolutionary selective advantage. Dogs have evolved certain muscles in their faces which are not present in wolves and these are responsible for the irresistible effect dogs have on humans. In fact, the ‘puppy dog’ effect is like that of someone who is sad or a child.