Dogs
Understand Spoken Words Better than We Thought
Dogs
are able to listen to different people saying the same word and recognize it as
the same word, ignoring the differences between speakers, and can discriminate
between unfamiliar people by the sound of their voice alone, according to
a new study published in the journal Biology
Letters.
Root-Gutteridge et al show that the ability to spontaneously
recognize both the same phonemes across different speakers, and cues to
identity across speech utterances from unfamiliar speakers, is present in
domestic dogs and thus not a uniquely human trait.
“Until now, the spontaneous ability to recognize vowel sounds when spoken by different people was considered to be uniquely human,” said Dr. Holly Root-Gutteridge, a postdoctoral researcher with the Mammal Vocal Communication and Cognition Research Group in the School of Psychology at the University of Sussex.
“But many dog owners
believe their dogs can learn a word from one person and recognize it when
spoken by a second or third person.”
“We wanted to test if
dogs can recognize the same phonemes — the little sounds that make up words —
when spoken by different people, ignoring the differences in accent and
pronunciation.”
Dr. Root-Gutteridge and
colleagues from the Defence Science and Technology Laboratory and the
University of Sussex filmed the reaction of dogs when they heard recordings of
men and women speaking a set of short words that sound similar to each other,
such as had, hid, heard and heed.
“To do this, the dogs
have to ignore cues which are used to identify people and perceive Sally’s
‘had’ to be the same word as Maggie’s ‘had,’ despite differences in their
voices and pronunciation, and realize it is different to Jane’s ‘hid’,” Dr.
Root-Gutteridge explained.
“Then we tested whether
dogs could also recognize people — who they had never met — by their voices
alone.”
Words were chosen that
are not usually associated with commands, so the dogs’ reaction could not be
due to training.
The dogs did not know
the speakers, so were not responding to the sound of a voice they recognized,
and they were not encouraged or rewarded with treats and attention.
The test results show
that dogs can spontaneously recognize short words as the same when spoken by
different people.
The dogs could tell the
difference when a word with a slightly different vowel sound was introduced.
This spontaneous ability
to differentiate words by subtle differences in vowel sounds has previously
only been recorded in humans.
“The ability to
recognize words as the same when spoken by different people is critical to
speech as otherwise people wouldn’t be able to recognize words as the same when
spoken by different people,” Dr. Root-Gutteridge said.
“This research shows
that, despite previous assumptions, this spontaneous ability is not uniquely
human and that dogs share this linguistic talent, suggesting that speech perception may
not be as special to humans as we previously thought.”
_____
Holly Root-Gutteridge et
al. 2019. Dogs perceive and spontaneously normalize formant-related speaker
and vowel differences in human speech sounds. Biol. Lett 15
(12); doi: 10.1098/rsbl.2019.0555
