Like humans, dogs have an episodic memory

Emily Brontë hit his very violently to the point of leaving him half blind. Le sien, it was Keeper, a dog who forgot, voluntarily or not, the prohibition to lie down on the beds and had, that day, received the promised correction, before being lovingly cared for by his mistress; it was also a dog who did not forget the writer after his death and remained prostrate in front of the door of his room at night, after having accompanied his remains during his funeral. A recent empirical study tends to prove that the best friend of the man has, like the latter, the episodic memory, but in a much more limited way in duration.

Lhitherto tests have only carried out on very few animal species, and scientists only recognized the possession of episodic memory in humans and certain apes, says Science & Life in an article from November 26 reporting the results of a study published three days earlier in the journal Current Biology, and whose summary is in limited access on the periodical website. Note that an experiment has already shown that pigeons have episodic memory with a memory that can be activated depending on the circumstances; these birds are capable of acquiring an abstract ordinal rule, they can react in ascending numerical order to figures as they have been taught. Children under the age of four are normally not capable of mental comings and goings in time.

The scientists subjected seventeen dogs to a series of tests like "Do like me!" Or "Do it!" », Which consists in teaching the animal to model its gestures on those of its master when the latter orders it. At first, the dog systematically receives a reward until it is able to imitate the master without gratification. The animal was then trained not to copy its master, until it was ordered to do as it did, without reward. Once this was supposed to be assimilated by the dog, his master touched in front of him an open umbrella lying on the ground without any order being given to the animal, before going away with him for an hour. On their return, the master told the dog "Do it!" », And the latter imitated the act of the former an hour before. A change of vision regarding cognition in the dog who had no motivation to consciously retain the gesture of his master.

The dog's madeleine of Proust

The image is known, it is that of the dog who pursues a person and abandons his objective to run behind a car which appears. This animal has a reputation for being easily distracted, and although it demonstrates an ability to remember certain commands, what makes its reputation more its fidelity, which assumes a semantic memory, like that of Keeper saddened by the loss of Emily Brontë, as her episodic memory. Some scientists suspected him of having one, but it was necessary to make sure of it by tests, and to find him for that a madeleine of Proust.

Proust's madeleine is the trigger for memories that can be an object, a word or a smell, that is to say, sensory stimuli, or mental effort. In the first volume of his novel In search of lost time, Marcel Proust evokes the return to his memory of details of his holidays when he was a child, thanks to a madeleine and a cup of tea. This memory, which appeals to the senses, to the affect - and which generally becomes semantic memory -, was defined by cognitive psychologist and neuroscientist Endel Tulving. An example given by Tulving to empirically demonstrate the activation of memory which makes it possible to speak of episodic memory, is the suggestion made to a student who had forgotten the word "yellow" among a list of unrelated terms, vocables mentioned by the psychologist. Tulving then asked the student if he hadn't left out a color, and the student instantly remembered which one. This was his Madeleine de Proust, like the memory of what we ate the day before. Episodic memory is that which must be activated by oneself or the exterior, unlike semantic memory. which is that of definitively acquired general knowledge: it is useless to make the slightest effort of reflection to know how to talk about your passion for cycling; but sometimes you need a trigger to remember a specific bicycle ride far away - and knowing how to do it definitely comes under procedural memory. And so it is this episodic memory distinguished by Endel Tulving that the experience brought to the fore in the dog. Ironically, Tulving did not believe animals could have this cognitive ability.

For Tulving, animals had acquired knowledge, but they were incapable of remembering lived experiences, of mentally traveling through time; they therefore had no interior unity, like the very young child. According to this diagram, Emily Brontë's dog, for example, knew who she was in relation to him according to the representation he had of her, possibly that she had beaten him, but could not make the effort to draw on his memory to remember the moment of violence experienced. The image of the dog changing target to run behind a car seemed to confirm the lack of inner unity in an animal whose life seems to unfold in the present. However, experience shows rabid dogs when they see a stick, as if they remembered being abused by it. One could suspect, for various reasons, perhaps this one, the existence of an affective-event memory which recorded the memories of subjective experiences to restore them on the occasion of an external or internal command, but it had to be demonstrated, and scientists excluded the dog from possessing this form of memory until this experiment.

This work, multiplied with several dogs, therefore suggests that this multimillennial human companion has an episodic memory. However, it would only last for a day before breaking down. For the main author of this empirical study, Claudia Fugazza, "Give them the order Do it after a while is sort of a way of asking them: Do you remember what your master did? Fugazza has trained cetaceans and parrots to imitate human actions, and she believes that further work may reveal that animals other than dogs or some monkeys have episodic memories.

Hans-Søren Dag

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