Crucially, the reward center was active only when dogs heard praise words in praising intonation.
Dogs, like humans, use the brain´s left hemisphere to interpret words and regions of the right hemisphere to analyze intonation.
But while evidence shows dogs can register and understand audio recordings, experts say pet owners should expect their four-legged friends to blatantly ignore them during video chats through FaceTime or Skype.
This shows a fairly sophisticated ability to comprehend language and intention, differing from human capacities perhaps only in degree, not kind.
In other words, just as people wouldn't want to hear complimentary language said to them in a less-than-complimentary way, the same is true for dogs - meaning if you want your dog to feel its happiest, you have to speak praise with praising intonation. "We let them listen to their trainer's speech and at the same time we measured their brain activities", explained study leader Attila Andics.
In 2014, Andics' team showed where dogs' voice processing regions were and how similar they are to us. One reward area didn't activate at all if positive words and positive tones weren't used.
While other species probably also have the mental ability to understand language like dogs do, their lack of interest in human speech makes it hard to test, said Andics. The language was processed in the left hemisphere, the same as in humans.
During the experiments, dog owners voiced different combinations of words and tones: praise words with approving intonation, praise words with neutral intonation, neutral words with praising intonation, and neutral words with neutral intonation. For instance, in one documenting the trainer would use positive words like "well done!" with a positive high-pitched tone.
That's a trick that might not always work.
It had already been established that dogs respond to human voices better than their wolf brethren, are able to match hundreds of objects to words, and can be directed by human speech.
However, dogs have socialized with humans for thousands of years, therefore they pay more attention according to scientists.
To determine this, the Hungarian researchers and colleagues at Eötvös Loránd University in Budapest trained a collection of family-owned golden retrievers and border collies to sit quietly inside an MRI scanner. Humans normally experience increased oxytocin in romantic encounters or after childbirth.
Still, as the authors note, if the study's findings prove to be robust, it could tell us a lot about the deep connections between humans and dogs, and perhaps many other animals.