We all know things that we can’t properly attribute; a bit of trivia, celebrity gossip, the best bakery in town, and yet we can’t remember who told us these things. It is possible to remember the name to a great new restaurant but not who first told you about it. Source memory was thought to be a uniquely human trait; looks like we are not as ‘unique’ as we’d like to believe.
Source memory encodes the origin of the information which is different from the information itself, the event. So how do you ‘ask’ a rat if it has source memory?
Taking advantage of rat’s inexhaustible love of chocolate, the experimenters ran various tests to separate behavior related location of memory and behavior influenced by source memory. Rats were able to learn whether they got chocolate from the experimenter or by their own work, self-generated. Under ‘experimenter’ conditions the chocolate site would not be replenished but in self-generated test the site would be replenished with more chocolate. The rats were far more likely to re-visit the location for self-generated tests than for experimenter-generated conditions. And finally because source memory decays differently from location memory the probability or revisiting and finding the food differed between the self-generated and experimenter-generated rats.
When taken together these tests converge to provide the first evidence that non-human animals have source memory. So a rat really does know how it got that chocolate. And if it’s true for a rat then it’s possible a dog also remembers how it got that treat or that treasured toy.
And what about other types of memory?
Crystal JD, Alford WT, Zhou W, & Hohmann AG (2013). Source Memory in the Rat. Current biology : CB PMID: 23394830
- A Difference of Degree and Not Kind (dogbehaviorscience.wordpress.com)