Do you recall what you ate for dinner last weekend? This ability is called episodic memory. As we age, our ability to recall specific times and places decreases. According to a new paper in the Proceedings of the Royal Society, Cuttlefish also exhibit episodic memory. However, unlike humans, this ability doesn't diminish with age.
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Alexandra Schnell, coauthor of the University of Cambridge and who carried out the experiments at the Marine Biological Laboratory, Woods Hole in Massachusetts, said that Cuttlefish can recall what they ate and where it was. It is amazing that this ability doesn't diminish with age, even though they show other signs of aging such as loss of appetite and muscle function.
We reported earlier this year on Schnell's and other colleagues' study that showed cuttlefish can delay gratification. They could also pass the cephalopod version, which requires them to wait a while for their favorite prey instead of settling for less desirable prey. A subsequent learning test also showed Cuttlefish's superior performance. This is the first time that a link between intelligence and self-control has been established in non-mammalian species.
The cuttlefish was given two options for prey: it could choose to consume the raw kingprawn right away or wait to get the live grass shrimp. The subject was able to see both the options and could choose to eat the king shrimp if it tired of waiting for the grass shrimp.
To assess cognitive performance, the team also put cuttlefish through a learning task. Researchers reversed the process so that the same reward could be associated with two different symbols. The researchers found that cuttlefish could wait for better rewards and can tolerate delays of up to 50 to 130 secs. This is comparable to large-brain vertebrates like chimpanzees and crows.
The latest study examines whether cuttlefish possess episodic memory, which is the ability to recall unique past events and provide context about when, where, and how it occurred. This ability is developed in humans around the age of 4, but our episodic memory decreases as we age. This contrasts with semantic memory, which is our ability to recall general knowledge in a context that doesn't include time and space. It has been demonstrated that semantic learning in humans remains relatively intact as we age.
The human brain's hippocampus plays an important role for episodic memory. It is believed that as we age, our episodic memories decline due to the deterioration of this region. Scientists believed that episodic memory was unique to humans because it is linked with conscious experience of recollection. These aspects can be expressed verbally by humans; however, it is much more difficult to assess the conscious experience of nonverbal (in human terms), animals.
However, many animal species have been shown "episodic like" memory abilities. This term is used by scientists in the subfield to "explicitly admit that we don't assume human attributes of language or consciousness involved in the awareness of the projections of self in time," Schnell et. al. In a footnote, Schnell et al. A 1998 study showed that jay birds could remember where and when they had stored their foraged food, as well as the specific food. Magpies, great-apes, rats and zebrafish also exhibit episodic-like memories.
Cuttlefish also show evidence of episodic-like memories. Cuttlefish do not have a hippocampus but they have a brain structure and organization that is similar to the connectivity and function human hippocampusi.e. learning and memory. Studies in the past have shown that cuttlefish can be future-oriented, optimize foraging behavior, and recall details from past forages. This is a hallmark of episodic-like memory. They adjust their strategy to change prey conditions.
