New Delhi: A new study suggests that dogs might segment human speech into words in a way seen only in humans, and that they might acquire this ability through regular, everyday exposure to human speech.
The findings indicate that efficient speech processing may not necessarily be a consequence of humans' unique language abilities, researchers say.
Regular exposure to speech alone can reshape how the brain functions, even in a mammalian species evolutionarily distant from humans, the findings published in the journal Science show.
The researchers from ELTE Eötvös Loránd University in Hungary explain that, in a continuous speech stream, it is easier to detect individual words when we focus on consonants.
"And from infancy onward, this is exactly what the human brain tends to do. This phenomenon is known as the consonant bias," Attila Andics, cognitive neuroscientist, head of the neuroethology of communication lab, and corresponding author of the study, said.
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But could consonant bias require complex language abilities unique to humans? The researchers compared the brain responses of 20 humans and 20 companion dogs to speech.
The participants, both humans and dogs, listened to continuous, unsegmented speech streams, which were of three types — three-syllable words with consonants forming word skeletons with freely varying vowels, vowels forming word skeletons, and syllables following each other randomly.
Brain electrical activity was measured using non-invasive EEG.
"In the consonant-structured speech streams, the dog brains, just like the human brains, successfully synchronised with the rhythm of the words. In both species, this synchronisation was stronger than in either the vowel-structured or the control streams. This is the first evidence that a consonant bias can also emerge in the brain of a species other than humans," Kinga G. Tóth, a psychologist, the study's other co-first author and a doctoral researcher in the group, said.
The researchers also observed a distinct change in the brain's electrical activity in both humans and dogs around 400 milliseconds after the beginning of each word, but only for consonant-structured words — the time window reflects the segmentation of continuous speech into individual words.
"The study also revealed that this tuning to the characteristics of speech does not emerge only in dogs that were already living in a speech-rich environment during the first months of life, when they are especially sensitive to social experiences. Dogs that had spent their first three months living on the street or in a shelter, rather than as family pets, showed a similarly strong consonant bias," Tóth said.
The result "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," the psychologist said.
