Did I see it or did I smell it? An investigation of source memory in cuttlefish
Résumé
Source memory refers to the capacity to retrieve the origin of a memory. This origin is remembered through conscious retrieval of specific features of the memory (e.g., perceptual, affective, contextual, cognitive information). In a source discrimination task, we studied the ability of cuttlefish to remember the modality in which a prey item had been presented (i.e., a visual or an olfactory presentation of a crab). In the first study, animals were trained to associate the modality of presentation of a crab with a visual cue placed in the tank (i.e., when I see a crab, I should go to the left visual cue to obtain a reward, whereas when I smell a crab I should go to the right visual cue to collect the reward). On test, cuttlefish were presented with visual or olfactory stimulations of crab, but at this stage they did not have the opportunity to make a choice between the visual cues. After a delay, the visual cues were placed in the tank, giving cuttlefish the opportunity to make a choice (i.e. to go to the left or right visual cue).
Our results showed that cuttlefish were able to remember the modality of the crab they had previously encountered. In the final test, the cuttlefish were tested with a novel prey they had never encountered before (i.e., shrimp). Results showed that cuttlefish were not able to remember the modality of presentation of the shrimp encountered before the delay, perhaps because they had made a specific association between the crab and the olfactory and visual presentations as opposed to a more general rule about the modality of presentation of prey items. In order to investigate this further, in a second experiment, cuttlefish were presented with three types of prey during training and passed several transfer tests with novel prey they had never encountered before. This time, all cuttlefish were able to remember the modality of presentation of the novel prey after a time delay. Taken together, these results show that cuttlefish could remember specific perceptual source information, namely whether they had seen or smelled the prey item.