I remember that the meal was not only about you, but also about cuttlefish

Remember the delicious meal you had at that unforgettable restaurant 20 years ago? Cuttlefish can also remember.

In a new study, researchers found that cuttlefish recall the entire experience of eating their favorite food — and, unlike humans, this ability increases with age.

In the human brain, some memories last longer than others. Memories of facts, such as where the grocery store was or the date of the first human landing on the moon — what scientists call semantic memory — don't usually fade with the passage of time. But people can also remember unique events in their lives, not only when and where they happened, but also the specific feelings we experience. This "episodic memory" tends to blur over time. Studies of pine birds, mice, and monkeys have shown that they also have both kinds of memories. Eight years ago, another animal joined the ranks: cuttlefish.

To find out how cuttlefish's memory changes over time, the researchers first tested their semantic memory, which is their recall of facts. The researchers tested their memory with the help of where they got their food each day.

Alexandra Schnell, a comparative psychologist at the University of Cambridge in the United Kingdom, and colleagues first trained 12- and 24-month-old cuttlefish to eat at specific locations in fish tanks. After 3 weeks, they tested the cuttlefish's ability to remember these locations. Even when scientists don't provide food, both young and old cuttlefish are in the right places for breakfast, middle, and dinner at the right time. This indicates that they have strong semantic memory.

To test episodic memory, the researchers added another variable: the animals' individual preferences. They served the cuttlefish two meals at the same time in two different places in the tank — one for the shrimp meat they didn't like and the other for their favorite live grass shrimp. They then offered two more meals at the designated location, but at different times: one hour after the first meal, there were shrimp, or 3 hours later, both shrimp and live grass shrimp.

After 4 weeks, the researchers had the cuttlefish swim to the right place at the right time to "choose" the food. Eventually, all cuttlefish learn to wait longer to get favorite live grass shrimp. Researchers recently reported in the Proceedings of the Royal Society b that this suggests that they have developed complex episodic memories, including not only where and when they ate, but also which meal was more delicious.

Daniel Osorio, a neuroscientist at the University of Sussex in the UK who was not involved in the study, said the study showed that the animals were really good at learning complex things. Many studies claim that cephalopods have intelligence, but few have been able to prove this in such a complex way. (Tang Yichen)

Related thesis information: https://doi.org/10.1098/rspb.2021.1052

Source: China Science Daily