Dr. Alexandra Horowitz, the research’s leader, wrote in her report: “While domestic dogs, Canis familiaris, have been found to be skillful at social cognitive tasks and even some meta-cognitive tasks, they have not passed the test of mirror self-recognition (MSR).”
She borrowed the pioneering ethological approach, called the “Sniff test of self-recognition (STSR)” proposed by Prof. Cazzolla Gatti in 2016 to shed light on different ways of checking for self-recognition, and applied it to thirty-six domestic dogs accompanied by their owners.
This study confirmed the previous evidence proposed with the STSR by Dr. Cazzolla Gatti showing that “dogs distinguish between the olfactory ‘image’ of themselves when modified: investigating their own odour for longer when it had an additional odour accompanying it than when it did not. Such behaviour implies a recognition of the odour as being of or from ‘themselves’.” Paper. (paywall) – Alexandra Horowitz. Smelling themselves: Dogs investigate their own odours longer when modified in an “olfactory mirror” test. Behavioural Processes, 2017; 143: 17 DOI: 10.1016/j.beproc.2017.08.001 More.
The mirror test isn’t a good one because it assumes that the animal understands what a mirror even is. The cognitive load of recognizing what a mirror image is and does is much greater for the dog than the cognitive load of recognizing himself by his own body’s smell. And he prefers to recognize things by smell.
Incidentally, why have some doubted that dogs have “self-recognition”? All it need mean is that the life form senses specific boundaries between itself and not-itself. What follows from self-recognition depends on the type of mind the animal has.
See also: Science Mag: Dogs understand vocabulary, intonation Of course. Otherwise, how would they distinguish between Bad dog, bad! and Good dog, good!
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Furry, feathery, and finny animals speak their minds
Animal minds: In search of the minimal self