Do our four-legged friends really understand what we say? Not exactly, say scientists - but dog brains process speech in much the same way as our own.
Hungarian researchers analysed the brain activity of dogs using magnetic resonance imaging while they heard commands.
The researchers found that, just like us, dogs process speech in two different parts of the brain, based on whether they “know” words, and on the tone of voice used to say them.
Intonation (such as when we praise a dog with a high toned voice) is processed in a lower part of the brain.
Meaning (such as whether you say a known word like “well done”) is processed in a higher part of the dog’s brain.
Hungarian researchers measured awake, cooperative dogs' brain activity via functional magnetic resonance imaging (fMRI).
Dogs listened to known, praise words (such as “clever”, “well done”, “that's it”) and unknown, neutral words (“such”, “as if”, “yet”) in several different intonations.
Anna Gábor, postdoctoral researcher at the MTA-ELTE 'Lendület' Neuroethology of Communication Research Group said, "Exploring speech processing similarities and differences between dog and human brains can help a lot in understanding the steps that led to the emergence of speech during evolution.
“Human brains process speech hierarchically: first, intonations at lower-, next, word meanings at higher stages. Some years ago, we discovered that dog brains, just as human brains, separate intonation and word meaning. But is the hierarchy also similar?
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Gábor said, “To find it out, we used a special technique this time: we measured how dog brain activity decreases to repeatedly played stimuli. During brain scanning, sometimes we repeated words, sometimes intonations. Stronger decrease in a given brain region to certain repetitions shows the region's involvement.”
The results show that dog brains, just like human brains, process speech hierarchically: intonation at lower stages (mostly in subcortical regions), while known words at higher stages (in cortical regions).
Interestingly, older dogs distinguished words less than younger dogs.
Attila Andics, principal investigator of the MTA-ELTE 'Lendület' Neuroethology of Communication Research Group said, "Although speech processing in humans is unique in many aspects, this study revealed exciting similarities between us and a speechless species. The similarity does not imply, however, that this hierarchy evolved for speech processing"
"Instead, the hierarchy following intonation and word meaning processing reported here and also in humans may reflect a more general, not speech-specific processing principle. Simpler, emotionally loaded cues (such as intonation) are typically analysed at lower stages; while more complex, learnt cues (such as word meaning) are analysed at higher stages in multiple species.
”What our results really shed light on is that human speech processing may also follow this more basic, more general hierarchy."