Dogs would say: size is important, shape - not so much
Ball? The mouth-sized chewy thing? Can I have a treat now
We here on the canine desk at Vulture Central have often pondered the mystery of how it is that dogs - with their own mental lexicon - understand words that relate to fetching specific objects such as "ball" or "bone".
Now animal behaviour academics at the University of Lincoln have collected empirical evidence that apparently shows that man's best friend has a way of dealing with words that is markedly different to that of human beings.
The study, which is published in the peer-reviewed online journal PLOS ONE, claims that the findings could help us advance understanding of the foundations of language in humans as compared with other species in the animal kingdom.
Humans are believed to group objects based on their shapes. Such classifications are thought to have an impact on how we developed language.
"A number of recent studies have suggested that the domestic dog's word comprehension is human-like," said Dr Emile van der Zee, who - along with two other colleagues at the university - observed the actions of a five-year-old border collie named Gable.
"Arguments have been made to refute this claim, but until now there has been no clear empirical evidence to resolve the debate. Our findings bring a fundamental new insight into this discussion and add to our understanding of the cognitive equipment necessary for true human word learning."
Gable, whose excellent sense of smell was excluded from the study for obvious reasons, was found to base his apparent understanding of words by first generalising on object size and then on object texture. But, the study explained, dogs - unlike humans - do not appear to naturally discriminate based on shape.
Young children develop what is known as "shape bias", which is said to be crucial to language development because it enables kids to assign new objects to pre-established classes, the eggheads added in their paper.
Gable underwent four different challenges to help researchers attempt to determine how the dog ticks in relation to his ability to understand language. They found:
On a number of occasions a selection of ten different objects known to Gable were placed in an enclosure out of sight of Gable and the researchers, and he was then given a verbal instruction to fetch a particular object from the ten.
Initial tests confirmed that Gable could easily distinguish between toys he knew well.
It was when the researchers introduced new words and novel objects of varying shape, size and texture that Gable began to reveal the absence of shape bias in his choices.
He appeared to make distinctions based first on object size, then, when he had longer to become familiar with the new objects, on the basis of texture. Object shape appeared to have no influence.
The psychologists concluded from their one-dog study that the long-term mental story containing sound-to-meaning mappings, which is referred to as the mental lexicon, was fundamentally distinct in mutts and humans. They argued that word knowledge development and word reference quality among Canis familiaris was different to that of Homo sapiens.
This sleepy mutt, following a three-year-long empirical study
by your correspondent, is NEVER EVER gonna fetch a silly ball
The apparent absence of shape bias in dogs - or in this case Gable the dog - could inform refinements to the training programmes for man's best friend, the researchers claimed.
"This [study] would suggest that an important factor in the natural structuring of the mental lexicon may be the way in which sensory information is organised in a particular species," argued Dr Van der Zee.
"The human visual system is tuned to detect object shape for the purpose of object recognition. In our experiments we excluded Gable using scent cues. It seems that his visual system and sensory cues linked to his mouth region are focused not on shape, but on size and texture.
"Only future experiments will reveal what role scent plays for the dog in generalising words. It is only by comparing other species with humans that we can find out more about the neural and genetic foundations of word reference in language."
The paper, Word Generalisation by a Dog (Canis familiaris); is Shape Important?, by Van der Zee, Helen Zulch and Daniel Mills is available here. ®