Dogs may link words to object sizes rather than shapes

Posted by Bridget in Biology, Life

Courtesy of the University of Lincoln and World Science staff

Dogs relate words to objects very differently than humans do, new research claims: whereas we relate words for objects primarily to their shapes, dogs relate these words to sizes and textures.

Many pet owners marvel at their dog’s ability to fetch different objects such as toys on instruction, taking this as evidence that the dog ‘understands’ these words in a similar way to us.

The new findings, published in the online research journal PLoS One, may help to advance understanding of the foundations of human language and the critical differences with other species, the researchers said.

Young children generalise names to new objects on the basis of shape, and continue to do so as adults – a tendency known as ‘shape bias,’ the scientists explained. This is key to language development because it enables children to assign new objects to pre-established classes – for example, to recognise that a tennis ball and a football both belong to the category ‘ball.’

The researchers worked with a dog and found that when he was introduced to new words to refer to new objects, he first generalised based on size, then on texture, but not shape.

‘A number of recent studies have suggested that the domestic dog’s word comprehension is human-like,’ said Emile van der Zee from the University of Lincoln in the UK, who carried out the research with two colleagues. Some have disputed that claim but there has not been clear experimental evidence, he added. ‘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.’

Four challenges

Van der Zee and two colleagues worked with a five-year-old border collie called Gable who had shown remarkable abilities to learn new object words. They devised four different challenges for Gable.

On a number of occasions, a selection of 10 different objects known to Gable was placed in an out-of-sight enclosure, and he was then given a verbal instruction to fetch one object from the 10. Initial tests confirmed Gable could easily distinguish between toys he knew well. However, when the researchers introduced new words and novel objects of varying shape, size and texture 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, the scientists explained. Shape seemed to have no influence.

‘This 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,’ van der Zee said. ‘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 findings may also inform refinements to animal training programs, the researchers added.

Source: World Science, http://www.world-science.net