Peter Pongracz and his team recruited 96 dogs of various breeds and ages and presented a test group of 24 of the dogs with two projected images of a large (over 60 cm) or small (under 52 cm) dog: one life-sized and one of the same dog scaled up or down by 30 percent.
They then played a recording of a food-guarding growl from either a small or large dog, with the sound coming from midway between the two images, reports a website.
20 of the 24 test dogs looked at the image of the appropriate-sized dog first and looked at it longest.
The control group presented with images of triangles showed little interest in the images, while those shown images of cats spent more time looking at them.
The control dogs looking at pictures of cats often looked first at the image on the left.
According to Pongracz, this ability of dogs is a "complex cognitive talent previously seen only in primates."
The research also showed that dogs do not lie about their size, and this is the first time research has shown animals can determine another's size by the sound it makes.
The results are published online in the journal PLoS ONE.