Love hormone explains why your dog loves to see you smile

Wild animals have more to gain from watching out for predators than getting all warm and fuzzy when they see a smiling human. But your dog is nothing like any other animal. A new study has revealed that your pet can love you so much that it might even ignore danger to see your smiling face. If you’re nice to it.

How often do you pet your dog? Gaze into its loving eyes? Smile at it? Hopefully, very often, because the more you do it, the more your dog will love you — and new research helps us to understand why.
Every time you gaze lovingly into your dogs’ eyes, its levels of oxytocin — the “attachment hormone” — go up. And so do yours.

Oxytocin has long been referred to as “the love hormone” and the “cuddle hormone,” because we (and our pets) release it when we hug, touch, or look lovingly into someone’s eyes. This increases our attachment to that person (or animal.)
But researchers already knew this. What they didn’t know was that more oxytocin also makes dogs prefer smiling faces over threatening ones — kind of like we do.
This may not sound like much in the human kingdom, but among animals — which have a better chance of survival if they’re attuned to threatening cues — it’s kind of a big deal.
The new study was led by Prof. Outi Vainio, from the University of Helsinki in Finland, and it was published in the journal Frontiers in Psychology.
The findings seem to reinforce a virtuous circle of affection between dogs and humans: the nicer you are to your dog, the more of the love hormone they will secrete. In turn, this will make them love you even more — so much so that they might even ignore danger for your sake.

Oxytocin makes dogs love your smile

In case you’re wondering how researchers could tell what a dog feels, the answer is pretty specific: by measuring the size of their pupils.
“We were among the first researchers in the world to use pupil measurements in the evaluation of dogs’ emotional states,” says Prof. Vainio. “This method had previously only been used on humans and apes.”
Larger pupils indicated higher emotional arousal. The researchers administered oxytocin nasally to the dogs, and, using an eye-tracking device, they examined both the size of the dogs’ pupils as well as the direction of their gaze.

They did so twice for each dog: once after they received oxytocin, and once without the hormone.

By default, dogs tend to focus more on the most salient aspects of a social situation — such as frightening cues in a dangerous situation However, oxytocin seemed to make them override this survival instinct; dogs that received oxytocin were far more interested in smiling human faces than threatening ones.
This was backed by their emotional response, which was also altered. Without the hormone, they responded emotionally more to angry faces — their pupils dilated more — while when they were under the influence of oxytocin, they responded more to smiling faces.
As the authors explain, this probably means that oxytocin makes angry faces look less threatening and smiling faces more attractive. Both of these signs indicate a higher pro-social behavior.
“Both effects,” says Prof. Vainio, “promote dog-human communication and the development of affectionate relations.”

“It seems that the hormone oxytocin influences what the dog sees and how it experiences the thing it sees,” adds doctoral student and first study author Sanni Somppi. And when that thing is your smiling face, your dog most probably loves it.

Oxytocin: The 'relationship crisis hormone'?

Oxytocin is widely known as the “love hormone” due to its beneficial role in social bonding and sexual reproduction. According to a new study, however, oxytocin isn’t all about the good times; it is also at play during periods of relationship insecurity.
Researchers found that when an individual feels that their partner is losing interest in their relationship, levels of oxytocin increase.
First study author Nicholas M. Grebe, Ph.D., of the Department of Psychology at the University of New Mexico in Albuquerque, and colleagues recently reported their findings in the journal Hormones and Behavior.
Oxytocin is a hormone secreted by the pituitary gland, a pea-sized structure in the brain that is situated just below the hypothalamus.
The role of oxytocin is vast. Not only is the hormone responsible for inducing contractions during childbirth, but it is also involved in mother-child bonding and sexual arousal. Its duties, however, may not end there.
The study from Grebe and colleagues indicates that the brain releases oxytocin in times of relationship crises, possibly in an attempt to “fix” the relationship.

Oxytocin tries to ‘take care’ of a relationship

The researchers came to their findings by enrolling two groups of adults. One group was comprised of 75 couples from the United States, while the other group consisted of 148 individuals from Norway who had a romantic partner.
“Participants in the study were asked to think about their partner and how they wish their partner would connect with them in the relationship,” explains study co-author Trond Viggo Grøntvedt, Ph.D., also from the Department of Psychology at the University of New Mexico.

Subjects’ oxytocin levels were measured before and after the thinking task.
The team found that participants who felt a strong personal investment in their relationship demonstrated an increase in oxytocin levels, which further supports oxytocin’s role in social bonding.

However, the researchers uncovered an interesting result when assessing partners’ oxytocin levels simultaneously.
Among couples in which one partner was more invested in the relationship than the other, the more invested partner showed a greater increase in oxytocin levels when they thought about their relationship.
The researchers suggest that this heightened increase in oxytocin may be an attempt to rebuild a relationship bond.
“What’s implied here is a statement about what oxytocin is doing: it’s perhaps fostering attention to and motivation to ‘take care of’ the relationship,” says study co-author Prof. Steven W. Gangestad, also of the Department of Psychology.

Oxytocin may not be able to ‘fix’ doomed relationships

However, the team found that there is a limit to oxytocin’s relationship-fixing efforts. Among couples whose relationship was heading toward breakup, the partner who was most invested did not show a significantly heightened increase in oxytocin levels.
Overall, the authors believe that their findings support the “identify and invest” theory in relation to romantic relationships, whereby the brain identifies a vulnerable relationship and tries to strengthen it.