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Dogs can process continuous human speech in a way previously observed only in humans, with their brains showing a preference for consonant-based word patterns, according to a peer-reviewed study by researchers at Etvs Lornd University (ELTE) in Budapest, published in Science.
The study found that dog brains, like human brains, synchronised more strongly with the rhythm of words when consonants formed the underlying structure of those words. Researchers said the finding provides the first evidence that a consonant bias can emerge in the brain of a species other than humans. The research was conducted by ELTEs Neuroethology of Communication Lab, where scientists compared the brain responses of 20 humans and 20 companion dogs as they listened to continuous, unsegmented speech. Words are made up of two main types of speech sounds: vowels and consonants. Although vowels are louder and more noticeable, consonants usually form the skeleton of words, said Attila Andics, cognitive neuroscientist and corresponding author of the study. In the experiment, participants heard speech streams in which consonants or vowels formed recurring three-syllable patterns, alongside a control stream containing no recurring patterns. The researchers recorded brain activity using non-invasive EEG and examined neural synchronisation, the tendency of brain activity to follow rhythms detected in sounds. The dogs brains showed stronger synchronisation with speech streams in which consonants formed the word structure than with vowel-structured or random streams. Human brains showed the same pattern. In the consonant-structured speech streams, the dog brains, just like the human brains, successfully synchronised with the rhythm of the words, said Kinga G. Tth, psychologist and co-first author of the study. Researchers also identified a change in brain activity around 400 milliseconds after the beginning of each word, but only when the words were structured around consonants. The timing corresponds to a window associated with the segmentation of continuous speech into individual words. The finding was also observed in dogs that had not spent their earliest months in speech-rich family environments. Dogs that had spent their first three months living on the street or in a shelter displayed a similarly strong consonant bias. This provides further evidence that consonant bias does not require pre-wired language-processing mechanisms that emerge during a specific early developmental period. Instead, this neural preference may also emerge through relatively simple forms of pattern learning, Tth said. The study also found differences between humans and dogs. Humans could detect words defined by vowel patterns, although less effectively than consonant-structured words, while dogs could not. In addition, both species processed syllable rhythms, but only human brains synchronised with the rhythm of individual speech sounds. The researchers said this suggests that humans process continuous speech at a finer resolution, with individual speech sounds serving as separate processing units, while dogs appear to process syllables as their smallest units. Taken together, these findings suggest that the brain's tuning to speech and specifically the emergence of consonant bias does not require a pre-wired brain and human-like language abilities, Andics said, adding, Instead, regular exposure to speech may be enough to change how the brain functions and to give rise to processing characteristics previously observed only in humans even in a species evolutionarily distant from us. (ANI)
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