After playing with their pooches, dog lovers experience the same surge of emotions as a mother with her infant, or the feelings linked with romantic love and friendship, say scientists.
Biologists Miho Nagasawa and Takefumi Kikusui, of Azuba University in Japan, reckon that it is all controlled by a single hormone-oxytocin.
AdvertisementTouted as the cuddle chemical" or the "love drug", oxytocin has been found to dampen stress, combat depression, and breed trust in humans.
Past studies on voles, mice and rats have also pinpointed the role of this hormone in pair bonding and social memory.
Considering all that, the researchers conducted a study aimed at finding whether social contact between two different species could also lead to a surge in oxytocin levels.
"Miho and I are big dog lovers and feel something changed in our bodies when gazed [upon] by our dogs," New Scientist magazine quoted Kikusui as saying.
For the study, they recruited 55 dog owners and their pets for a laboratory play session.
After providing a urine sample to measure oxytocin levels, the owners played with their dog for half an hour, and then went through another urine test.
On the other hand, some owners acted as control and sat in a room with their dog and were told to completely avoid the gaze of their pets.
Kikusui's team videotaped the sessions and measured how long a dog spent eyeing its owner.
After the analysis, they split the pairs that were allowed to play into two groups: "long gaze", who locked eyes for an average of 2.5 minutes during the play session, and "short gaze", who made eye contact for fewer than 45 seconds, on average.
It was found that these groupings led to changes in owner's oxytocin levels-pet owners who spent a long time making eye contact showed a 20 percent boost in oxytocin levels, while owners in the control group saw their oxytocin levels drop slightly.
The researchers saw that long-gaze owners tended to rate their relationship with their pet as more satisfying than short-gaze owners.
In fact, despite being asked to avoid eye contact during the control session, these owners experienced a mild boost in oxytocin.
Kikusui said that a flood of the cuddle chemical could explain why playing with dogs can lift moods and even improve symptoms of anxiety and depression.
They even suggested that oxytocin might have played a part in the domestication of dogs from wolves, about 15,000 years ago.
"Maybe during the evolutionary process, humans and dogs came to share the same social cues", such as eye contact and hand gestures, said Kikusui.
He added: "This is why dogs can adapt to human society."