At first glance, octopuses may seem like “just” strange sea creatures with eight appendages, but in reality they rank among the most intelligent animals on Earth. They have a complex nervous system, learn from their own experience, solve problems, and—according to many observations—remember very well who treated them kindly and who harmed them. In recent years, studies have also emerged showing that octopuses can deliberately throw objects at other octopuses—which looks suspiciously like “passive-aggressive” behavior.
In this article, we’ll look at what research says about octopus memory, whether it makes sense to say they “hold grudges,” why they throw shells and sand at things that bother them, and whether there are other animals with a similar combination of strong memory and the ability to “take offense.”
How an octopus brain and memory work
An octopus doesn’t have a brain as a single ball of nervous tissue in its head the way humans do. A large share of its neurons are distributed throughout its arms, which have their own “mini-brains.” Altogether, an octopus has hundreds of millions of neurons—more than many small mammals—and while its nervous system is organized differently, it can rival them in complexity.
Scientific papers on cephalopod cognition describe octopuses as having at least two main learning and memory systems: a visual system (what they see) and a chemotactile system (what they “taste” with the suckers on their arms). These systems connect to a brain region called the vertical lobe, which plays a key role in forming long-term memory.
Research suggests that, like mammals, octopuses have separate short-term and long-term memory. Short-term memory helps them handle immediate tasks, while long-term memory forms through repeated learning and is stored in the vertical lobe. That means an octopus can remember for a long time, for example, which object signals food, which place is dangerous, or who it’s not worth “starting something” with.
What octopuses can remember
Laboratory experiments with the species Octopus vulgaris have shown that octopuses learn to distinguish between different shapes, patterns, and objects—and remember these distinctions long-term. In classic trials, octopuses are given two visual cues—say, a circle and a square—and receive food only after touching one of them. With repetition, they learn to reliably “choose the right one,” and they can retain this skill even after a longer break.
Beyond simple shape discrimination, octopuses can also handle more complex tasks, such as solving mazes or opening screw-top jars. In practice, this means they remember not only a specific shape or smell, but also a procedure—a sequence of steps that leads them to food or shelter. Such abilities suggest their memory isn’t merely short-term and mechanical; it also includes elements of spatial orientation and planning.
If an octopus once learns that a particular object is unpleasant—such as a net it was caught in or a tool used by a keeper to handle it—over the following days it will often react defensively to it, hiding, changing color, or trying to flee, even if the stimulus is no longer directly painful. That’s a typical sign that the memory has been stored in the brain and is influencing its behavior.
Do octopuses remember grudges—and people?
Stories from aquarists at various aquariums describe octopuses that clearly seemed to remember specific people. They would swim up curiously to one keeper and accept food from their hand, while with another person they would cower in a corner of the tank or splash water at them. Although these are anecdotal observations, they fit with what we know from experiments—octopuses can associate visual information (face, body shape, clothing) with a pleasant or unpleasant experience and remember that association.
Researchers caution that talking about “grudges” is somewhat anthropomorphic—projecting human emotions onto animals. Biologically speaking, it’s more accurate to call it associative memory: an octopus remembers that a particular person means stress, pain, or handling, and next time it tries to avoid them or intimidate them. From our human perspective, it can look like being offended or seeking revenge, but at its core it’s adaptive behavior meant to increase survival odds.
When we combine these observations with the fact that octopuses have a sophisticated learning system and long-term memory, it’s fairly reasonable to say they “remember wrongs”—at least in the sense that they can avoid someone who harmed them for a long time and respond to them differently than to a neutral person.
Why octopuses throw shells, sand, and objects
In recent years, scientists have been intrigued by a study that documented in detail the behavior of wild Octopus tetricus off the Australian coast. Using underwater cameras, researchers observed that octopuses often use a jet of water from their siphon to “shoot” shells, bits of algae, and sand from the area between their arms forward. They called this behavior “debris throwing.”
Interestingly, not all throws are the same. Sometimes octopuses throw material while cleaning a shelter or feeding—this may simply be a byproduct of what they’re doing. In other cases, however, they throw shells or sand toward other octopuses, often during conflicts or when an unwanted suitor tries to approach a female. The study found that certain individuals—especially females—hit the “target” more often, and in some situations it looked as though they really were trying to strike or drive someone away.
So some throws may be accidental, but a portion appears deliberate. Whether it counts as “revenge” or “anger” remains an open question, and scientists are cautious. What we do know is that octopuses can recognize an unpleasant situation, remember it, and in a similar situation later choose an active defensive mechanism—and throwing material may be one of them. In plain English, you could say that when someone keeps bothering them, they can literally “throw a shell” at them.
Do octopuses throw things at people, too?
In direct contact with humans, more common octopus behaviors include splashing water, fleeing, changing color, or trying to feel a person with their suckers—which can be curiosity as well as a way of checking whether something is a threat. Aquarists, however, also describe situations in which an octopus “spat out” or shot an object toward a person who was irritating it, or tossed pebbles toward the aquarium glass when a particular visitor approached.
Formal experiments specifically on “throwing things at humans” are still rare, so here we’re working mostly with observations and keepers’ experience. Combined with studies describing debris throwing at other octopuses in the wild, these accounts make sense: an octopus may perceive a person as a disturbing or threatening stimulus and use the same behavioral repertoire it employs in conflicts with its own species.
Video: an octopus solves a maze and shows its memory
If you’d like to visualize how octopuses learn and solve tasks, it’s worth watching a short video in which an aquarist describes a maze project for an octopus and shows how the animal can remember the route to rewards.
Projects like these aren’t classic laboratory experiments, but they illustrate well how quickly octopuses can learn and how firmly they can retain new experiences.
Do octopuses have “emotional” memory?
In the discussion of whether an octopus “remembers a wrong,” it’s important to separate two concepts: emotional experience and memory. Research on cephalopods has shown that their nervous system is complex enough for them to perceive pain and stress, which in some countries has led to laws protecting octopuses in experimental research similarly to vertebrates.
But memory is a separate layer—the animal stores not only “that was unpleasant,” but also “where, when, and what caused it.” When a future cue connects to that memory, a defensive reaction is triggered. To us, this resembles feeling wronged, because we too react more sensitively to those who have hurt us. It’s unclear to what extent an octopus experiences anything like human anger or resentment, but behaviorally it certainly acts that way—avoiding the culprit and, if needed, attacking.
Is there an animal with memory similar to an octopus’s?
If we look beyond the sea, we find several animals that combine excellent memory with the ability to “remember wrongs” in the sense of distinguishing between friendly and hostile individuals.
Among the best known are ravens and crows (collectively known as corvids). Experiments have shown they can recognize human faces and remember them for many years, responding to “enemies” with alarm calls and even attacks. Interestingly, they also pass this information on—young birds learn who to fear simply by watching older individuals’ reactions.
However, an even closer relative of octopuses with remarkable memory is the cuttlefish. Recent research has shown that cuttlefish can retain so-called episodic-like memory—memory of “what–where–when”—well into old age. In experiments, they remembered what type of food they got at which location and at what time, and used that to plan where it was worth going for the next feeding. Unlike in humans, this kind of memory did not decline with age.
Among large land animals, elephants are often mentioned: they remember water sources long-term, the faces of other elephants and humans, and can react aggressively to scents or sounds associated with poachers, while not responding the same way to tourists. In them, too, we see a combination of rich memory, social learning, and selective behavior depending on who harmed them in the past.
The difference is that elephants and corvids are vertebrates with brains more similar in structure to humans, whereas octopuses and cuttlefish are mollusks. That evolution arrived at similarly complex memory in two such different branches is fascinating in itself.
Is it fair to talk about “offended” octopuses?
From a scientific standpoint, we should be cautious about assigning purely human emotions to animals. An octopus certainly doesn’t think in words like, “I’ll get back at that diver one day.” Even so, we know it has advanced memory, can form associations with specific people and situations, and uses those memories to guide future behavior.
Practically speaking, that means if we treat an octopus roughly or aggressively, it will likely remember and respond more defensively next time—by fleeing, changing color, adopting an aggressive posture, or even throwing an object or jetting water. If we behave calmly and respectfully, it may be curious, swim closer, and explore us with its suckers.
So perhaps it’s fair to put it simply: octopuses remember very well who did what to them. Whether we call that “holding a grudge” or “learning from unpleasant experiences” is mostly a matter of wording. What matters is that these creatures aren’t just “sea monsters,” but thinking and feeling animals that deserve a measure of respect.
Sources
- ZARRELLA, I. et al. Learning and memory in Octopus vulgaris. Current Opinion in Behavioral Sciences, 2015. Available at: https://loewenstein.huji.ac.il/sites/default/files/yonatanloewenstein/files/1-s2.0-s0959438815001063-main_2011_11.pdf
- JOZET-ALVES, C. et al. Cephalopod learning and memory. Current Biology, 2023. Available at: https://www.sciencedirect.com/science/article/pii/S0960982223010564
- GODFREY-SMITH, P. et al. In the line of fire: Debris throwing by wild octopuses. PLOS ONE, 2022. Available at: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0276482
- SCHNELL, A. K. et al. Episodic-like memory is preserved with age in cuttlefish. Proceedings of the Royal Society B, 2021. Available at: https://royalsocietypublishing.org/doi/10.1098/rspb.2021.1052
Jana
I like turning curiosity into words, and writing articles is my way of capturing ideas before they slip away — and sharing them with anyone who feels like reading.
