Cuttlefish could potentially hold a grudge for their entire lives, as recent research found that their episodic memory – their recall of past experiences – doesn’t deteriorate with age. This makes them unique to humans and non-human mammals, whose episodic memory declines with age. It’s possible that the deciding factor is the hippocampus – or more the lack thereof, as cuttlefish, the apparent masters of long-term episodic memory, don’t have one, while us forgetful mammals do.
“Cuttlefish can remember what they ate, where and when, and use this to guide their feeding decisions in the future,” said first author on a new paper, Dr Alexandra Schnell of the University of Cambridge’s Department of Psychology, UK, in a statement. “What’s surprising is that they don’t lose this ability with age, despite showing other signs of ageing like loss of muscle function and appetite.”
The new research, published in the journal Proceedings of the Royal Society B, represents the first time an animal’s memory of past events has been found not to deteriorate with age. Carried out by an international team of researchers, the study challenged common cuttlefish (Sepia officinalis) of varying ages to a series of memory tests. Half of the subject group were juveniles while the other half were what you’d consider an elderly cuttlefish, the equivalent of a 90-year-old human.
They were trained to respond to feeding flags which would eventually be associated specifically with one of two food options: live grass shrimp (the favorite), or a less desirable snack of prawn meat (existing research has already found they will save themselves for preferred food, can pass the "marshmallow test" and make complex dinner choices).
After providing the two food types in two separate locations, they began to test the cuttlefishes' time-keeping skills by offering the less desirable food at one spot while the more desirable meal of a live shrimp popped up elsewhere, but only every three hours.
Next came the test, as the researchers wanted to see if the cuttlefish had retained the what-where-when information that would demonstrate if the older cuttlefish had poorer episodic memory compared to the wee young’uns. Sure enough, their results showed that all of the cuttlefish were capable of watching what food appeared at the flag cues and using this information to decide where to go next in pursuit of precious shrimp.
“The old cuttlefish were just as good as the younger ones in the memory task – in fact, many of the older ones did better in the test phase,” said Schnell. “We think this ability might help cuttlefish in the wild to remember who they mated with, so they don’t go back to the same partner.”
While our episodic memory sits in the hippocampus, an area of the brain that undergoes change as we age, the episodic memory of cuttlefish sits in the “vertical lobe”. This region stays the same right up until the final few days of the animal’s life, which the researchers say could explain why their episodic memory remains so good even as geriatric cephalopods.
This late-stage talent could help the cuttlefish spread their DNA far and wide when they begin mating towards the end of their life. By remembering who they’ve been with, where, and how long ago, they could effectively squeeze in as many partners as possible before taking a much-needed – and very much permanent – rest.
So, unless you want lifelong beef with a cuttlefish you'd best stay on their good side. Who knows how long it will be before these eerily intelligent, many-armed wonders come to settle some scores on land.