The cuttlefish (Sepia ofcinalis) can discriminate between two sensory modalities, vision and olfactory; this is no small feat. In order for us to perceive and respond to different senses and remember them, we need to possess episodic memory–the ability to go back, mentally, into our personal past–and be engaged in source-memory. Source memory allows us to distinguish between various episodic memories. Typical studies use “item versus source-memory discrimination task” to evaluate source-memory capabilities. For example participants need to distinguish between objects they had interacted with, and novel objects and understand the context of how each item was presented. This process relies on perception, the ability to understand and store information, and being able to go back and access that information later on. Cuttlefish use olfactory and visual cues for various behaviours such as choosing appropriate mates or camouflaging into their surroundings to hide from predators and prey. During mating season the cuttlefish communicate with their conspecifics (same species) visually by altering patterns and texture on the surface of their body, and also using chemical cues when selecting available sexual partners. Their ability to discriminate between the two modalities has been demonstrated, for the first time with animals, through Billard et al.’s two experiments done in 2020.
Prior to the two experiments, cuttlefish went through pre-training–learning how to approach a panel to get food–and training–learning to approach a distinct panel based on the circumstances, ie: visual, olfactory, or control cues (the 3 panels were distinctly marked and each corresponded to the previous 3 circumstances). Once the cuttlefish were successfully trained (8 out of 10 successful consecutive trials), the experimental phase proceeded. Experiment 1 tested whether the cuttlefish could distinguish between
SEE or SMELL stimulations. The criteria were SEE a crab versus SMELL a crab. In order for the cuttlefish to pass, they needed to approach the correct panel they had been trained to associate to one or the other cues. This test was performed throughout two days, the first of which there was a one hour delay between the stimulus and the insertion of the panels. During day 2 the delay was increased to three hours. A transfer test was then applied. This tests whether the cuttlefish can distinguish between a novel prey’s visual versus olfactory cues after learning the crab’s characteristic cues. What was found was that cuttlefish were able to distinguish the type of the stimulation however had trouble generalizing the discrimination rule of SEE versus SMELL between crab, and novel prey. In order for them to generalize and learn this rule, experiment 2 exposed them to novel prey without a delay after training and all cuttlefish were successful with the transfer test with a delay following that.
This study provides the first evidence that cuttlefish can perceive and retrieve visual and olfactory stimuli. This finding is an advancement in the study of animal cognition and opposes the thinking that humans are the only ones that possess episodic cognition. What is fascinating is that the cephalopods developed their centralized nervous system apart from vertebrates. This means the cognizance they possess could be acquired in a completely different manner than that of ours. Even though they elicit a behavioral result during a discrimination task, similar to vertebrates like humans, the mechanism for deriving the result could be quite different. Future studies could test if cuttlefish are able to retrieve more than one signal from their episodic memory and be able to contextualize them into one representation for that can prove even more so that cuttlefish’s awareness is highly advanced.
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