Cephalopod Consciousness Part 3: The Case for Cephalopod Consciousness

Here it is, finally: the post you’ve been waiting for. Having already convinced you that you should care about the possibility of consciousness in cephalopods in Part 1 and having briefly outlined the state of research on consciousness in non-human animals in Part 2, I’ll get right down to it and discuss the possibility of consciousness in cephalopods in this post. If you’re unfamiliar with the topic, I suggest reading Parts 1 and 2 of the series – in this article, I’ll be very brief with explaining some concepts that are explained in more detail there.

In this post, I’ll reference Jennifer Mather’s 2008 article (which I can’t recommend highly enough) “Cephalopod consciousness: behavioural evidence” and Edelman and Seth’s article (which is also an excellent read) “Animal consciousness: A synthetic approach”. These are both review articles, so I’ll be citing their descriptions of other people’s experiments a lot – I know this is bad practice, but hey, this is a blog – I can get away with it. I’ll cite a research study itself if I discuss it detail, but I’ll mostly be sticking to the arguments outlined in these two papers.

If you’ll remember from the last post in the series (and I’m sure you do, but I’ll summarize here anyways,) there are several methods that researchers use to get at the question of consciousness. Most directly, there is accurate self-report, whose use is limited to animals with whom we can communicate through language. This is not a useful approach with cephalopods, who (thus far) are not known to use language.

In the absence of language, animals can be trained to report on their experience (such as by performing a task for a reward when they detect a certain stimulus.) This approach is not well developed in cephalopods. Octopuses have been trained through reward and punishment to attack certain stimuli and not others in many studies; despite this, there is no protocol (that I know of) that to train octopuses with a task that would allow hypotheses about the animal’s awareness of its own experience to be tested directly in the ways that has been done for primates (for example.) Nevertheless, there is some evidence suggesting that cephalopods may be consciously aware from studies that use specific trained tasks.

Mather makes the point that the ability of cephalopods to learn a variety of tasks reliably and quickly, and then to forget them afterwards, makes them good candidates for at least primary consciousness because it implies the sort of behavioral and cognitive complexity that appears to be associated with consicousness in vertebrates. As an example of this, when experiments on visual discrimination in the octopus were done (mostly by M. J. Wells in the 1970′s and earlier,) experimenters attempted to discover the basis by which octopuses discriminated between two visual stimuli. In a sense, they were looking at how the octopus categorized stimuli. A number of hypotheses were generated to explain this within a simple, computational framework, but it was eventually concluded that octopuses (that is, individuals of the species O. vulgaris, the common octopus) don’t use a set of simple rules to categorize objects. Rather, Mather argues, they “[evaluate] a figure on several dimensions and [generate] a simple concept, where [a] concept is an abstract or general idea inferred or derived from specific instances.” Other evidence for the ability of cephalopods to exhibit learning like that taken to indicate cognitive ability (and thus the potential for consciousness) in vertebrate species comes from more complex learning tasks. The spatial learning abilities of cephalopods have been studied and it has been found, in general, that they might be capable of spatial learning to rival that of commonly used vertebrate laboratory species (such as rodents,) as long as the apparatus used is adapted to their capabilities (obviously, we cannot expect a rat and a cuttlefish to learn the same things in the same circumstance, but both can show impressive spatial learning given the right circumstances.)

Consciousness can also be suggested by non-trained behavior of an animal. As I’ll address at more length in a little bit, such evidence in cephalopods is found in accounts of their foraging behavior, their responses to novel objects in their environment, and the presence of sleep-like (and possibly REM-like) states. Most convincingly, in my mind, is the evidence suggesting the superior behavioral flexibility of cephalopods.

One of the more straight-forward tasks that is used to suggest conscious awareness in human and non-human alike is the mirror self-recognition task (MSR). What happens when you show a cephalopod a mirror – does it recognize itself, or does it treat its reflection as if it were another animal? Mather cites a personal communication suggesting that cuttlefish fail the MSR. You can see for yourself, in this great video of a cuttlefish at Epcot being shown its own image on an electronic screen. It turns very dark and pursues its image as if it were confronting another cuttlefish. The mechanics are a bit different, but it’s essentially similar to the MSR:

Mather makes a case for the cognitive abilities of cephalopods using the results of a study that looked at the strategies that octopuses use to open bivalves (which she discusses in this interview on Scientific American.) Not only do octopuses use different techniques for opening clams of different species (that is, they pry open the shells of the weaker ones, and drilling holes through the shells of the stronger ones, but they could switch strategies if one wasn’t working properly. When the experimenters took the clams that the octopus normally ate by prying open and wired them together so that they couldn’t be opened, the octopus figured this out and started drilling. This sort of behavioral flexibility, particularly the selection of one possible behavior among many on the basis of its effectiveness in a specific situation, could be attributed to some sort of centralized “executive processor” that might associated with consciousness.

Although definitions of “play” are often disagreed-upon, Mather argues that some octopuses have been observed playing with objects. While the existence of play behavior in a species is not indicative of consciousness, it suggests the possibility of consciousness; object play is, as Mather says, “something that intelligent animals do” to allow them to learn about things in their environment. (You can read my discussion of one study of octopus play at this link.)

It has also been (rather famously) argued that some octopuses have evolved the ability to use tools – specifically, one species of octopus (Amphioctopus marginatus) has been seen carrying empty coconut shells across the sea floor, which they use as mobile shelters. It can be argued that tool use is only possible when the animal using the tool has developed some rather sophisticated cognitive awareness of their surroundings that allows them to appreciate how an object can be used for a certain function. Here’s a video of this behavior, taken by one of the authors of the 2009 paper on the subject:

The comparative neuroanatomical argument for consciousness (epitomized by Panksepp’s “triangulation” approach to the problem, which recommends using affective, behavioral, and neural approaches together to infer consciousness in non-humans) is much more difficult to make for cephalopods than it is for vertebrates. The reason for this is simple: humans are vertebrates, and share many features of the anatomical and functional organization of our brains with other vertebrates. If you dissect a rat brain and a human brain side-by-side, most of the parts in one of them will show up in the other one in some form. Thus, it is rather easy to make an argument from analogy claiming that, because the brain activity and behavior of the two species in some situation are similar, it is likely that their experiences are likely to also be similar. It is harder to make this argument between people and cephalopods, because there is no direct equivalence between any of the parts of a cephalopod brain and the parts of a human brain, with the possible exceptions of the retina and primary visual processing areas of the two species and some parts of memory systems (eg. the vertical lobe system in cephalopods and the hippocampus in humans.) Even these are examples of convergent evolution (meaning they started from different places and got the same functional result,) and so the equivalences between these two brain areas in cephalopods and humans are only approximate, and based on a very limited knowledge of the functions of the cephalopod brain. Despite this difficulty, there are some overall features of the cephalopod brain that suggest consciousness, including its apparent organization as a complex integrator for sensory information, its lateralization, and its patterns of activity during sleep and wakefulness.

Edelman and Seth argue that we have a good reason to suspect that birds have some sort of consciousness, based on apparent anatomical and functional correspondence between the brains of mammals (including humans) and birds. They show this figure, which illustrates this correspondence – it shows diagrams of a human brain and a finch brain, with homologous structures colored similarly in each diagram:

As you can see, human and zebra finch brains (and indeed, mammalian and avian brains in general) have somewhat similar layouts, which allows one to make an argument for the inference of similar subjective states that correspond to certain types of neural activity in multiple vertebrate species. The basic logic is simple: if the brains are similar, and most of the output of the brain (that is, behavior) is similar in a certain situation, the rest of the output of the brain (that is, affective and/or conceptual awareness, eg. consciousness) is reasonably likely to be similar.

At the bottom of the figure, though, they show the octopus brain. Notice that it’s done in a completely different color scheme. This is because the functional or anatomical subunits of the octopus brain are not clearly equivalent to those found in vertebrate brains. A few localized functions of the octopus brain can be compared to those of vertebrate brains – for one, the vertebrate retina and the octopus optic lobe have apparently analogous structures and functions (that being the initial processing of visual information,) and the vertical lobe/medial superior frontal lobe system of the octopus is known to be involved in memory consolidation, and may have a microscopic structure that resembles that found in the mammalian hippocampus (for more info on this, check out Young, 1991, who makes the argument that the cellular structure and computational properties of the mammalian hippocampus might resemble those of the octopus memory system.)

Functionally, however, it is possible to find similarities between cephalopod brains and vertebrate brains, even if it is difficult to do so anatomically. Mather discusses the evidence for lateralized specialization of function in the cephalopod brain at length (that is, the general feature of the brain that two mirror-image halves can work somewhat independently, and may have different functions.) Lateralization is seen in humans and other primates, and seems to be one evolutionary result of the need for cortical tissue to be both locally differentiated and highly interconnected; it allows for more specialized cortical areas, because the right and left sides of the brain need not be functionally equivalent. Thus, the apparent laterality of the octopus brain (as this is already getting on in length, I’ll let you check out Mather’s article for a more complete discussion) might suggest that it has also evolved the sort of complex cognitive capacities that lateralization is associated with in mammals.

Finally, EEG-like recordings have been done in both octopus and cuttlefish, leading to the general (but very preliminary) finding that cephalopods have complex, low-frequency “background” electrical activity in some parts of their brains that seems to vary with their states of consciousness. In addition, they show sensory-evoked changes in this activity, in the same way that human EEGs do. This suggests that some of the gross functional properties of the cephalopod brain might resemble those of mammals on a system-wide level.

All of the arguments by analogy should be taken with a grain of salt, because while it is interesting to consider the possible theoretical importance of the apparent similarities between octopus and vertebrate brains, it seems premature at this point, given how little we know about them. While laterality, distributed low-amplitude electrical activity, and a certain kind of memory system architecture are found in the brains of animals who are almost definitely conscious (eg. mammals and birds,) it’s hard to say that their presence in such highly divergent nervous systems (eg. those of vertebrates and cephalopods) has the same set of functional consequences in all cases.

So there it is – these are the arguments for consciousness in cephalopods. It’s an astoundingly complicated and difficult question, and one that I’m sure I haven’t done justice to. Look for the last planned article of the series later this week, where I’ll reflect upon these arguments and figure out where I stand (and also hopefully invite discussion) on the science of cephalopod consciousness.

Thanks for reading!

P.S. Today is my first day of classes for the Fall semester. Wish me luck!

MATHER, J. (2008). Cephalopod consciousness: Behavioural evidence Consciousness and Cognition, 17 (1), 37-48 DOI: 10.1016/j.concog.2006.11.006

Edelman, D., & Seth, A. (2009). Animal consciousness: a synthetic approach Trends in Neurosciences, 32 (9), 476-484 DOI: 10.1016/j.tins.2009.05.008

Young, J. (1991). Computation in the Learning System of Cephalopods Biological Bulletin, 180 (2) DOI: 10.2307/1542389

Finn, J., Tregenza, T., & Norman, M. (2009). Defensive tool use in a coconut-carrying octopus Current Biology, 19 (23) DOI: 10.1016/j.cub.2009.10.052


  1. tonmo says:

    Retweeted – nicely done.

  2. JR says:

    most of your arguments are assumptions and highly theoretical. You must not mix intelligence (in its wide spectrum), complex behavior and consciousness. A computer can learn, but it is not conscious of itself.
    I think you should emphasize more on the different levels of consciousness.
    Also, from a scientific point of view, the comparison vertebrate brain / mammalian brain / invertebrate brain is very dangerous, functional, evolution wise and morphologically. Even if Cephalopods have an area specialized for memory and learning, it does not necessarily mean, that this area is (functional) homolog to the mammal hippocampus!
    I recommend the papers from Onur Güntürkün, he played a major role in relabeling the birds brain, and he wrote some interesting reviews.

    Nevertheless, I love your blog ;)

    • Thanks for the comment!

      I’ve tried to steer clear of actually claiming anything outright about whether or not cephalopods have consciousness (and it would probably be only primary consciousness, if anything,) because the arguments for that position (as you point out) require a lot of (blind) inference. However, I’m convinced that cephalopods are a good candidate for further study on the possibility of consciousness.

      The hippocampus/vertical lobe analogy is one that I myself don’t quite buy, except in the most general sense – ie. in the sense that a tic-tac-toe-playing computer made out of tinker toys ( http://www.retrothing.com/2006/12/the_tinkertoy_c.html ) and a my PC both use the same sort of mathematics to accomplish tasks. They may have similar computational properties (based on very preliminary anatomical evidence), but we’ve yet to solve what that means in terms of large-scale brain function.

  3. Bunche says:

    Hi Mike-

    I just heard about this site today, and it made my summer. I have been a lifelong lover of sea life — Jacques Cousteau was my god when I was a kid — especially the beautiful and graceful cephalopods, so this is right up my alley. Please keep it coming.



  4. Govinda Dickman says:

    Most philosophical enquiry into the nature and essence/substance of consciousness, and most actual experimentation into same, is defined-at-root by a very anthropocentric definition of consciousness.

    Typically, the seeker of this type of knowledge seeks to compare the objects, mechanisms and functions of other beings’ being to that of their own, usually in order to attain some sort of instrumental power over that object: to predict, to understand, to control.

    Levinas would have pointed out that this approach precludes learning because it precludes discourse with the “object of investigation”, and locks the investigator into a paradoxical DIALOG with their own projections, effects and affects. It is the difference, he would say, between encountering Other (which is merely a shadow of our psycholinguistically constructed Self) and encountering actual alterity…

    Interestingly, this problem pertains even in the ontological investigation of our own phenomena: as mentioned before, we tend to anthropocentrically instrumentalise and objectify everything we encounter, and this projective quality is all but invisible to us: we cannot see the colour of our own eyes, cannot see the ripples we cause, cannot see beyond the horizon that our existential “location” entails.

    It is astounding to me, that we should believe we may have ANY epistemological access the subjective phenomena of other beings, when we are so mawkishly inept in dealing with our own!

    • Thanks for the comment!

      The psychology of consciousness and cognition, I have found, tends to deal very little with the problems that occur when we infer things about the properties of the consciousness of others. I suppose that if it had to deal with these problems before proceeding, it would probably not get anywhere very fast. My personal view is that these experiments don’t actually say anything about consciousness – that can only be speculated about based on an always somewhat flawed analogy to people (to one’s self, more specifically.)

      The experiments I’ve talked about here are valid in that they measure the effects of certain manipulations on a system, and can do it reliably. The conclusions we can draw from them are concrete, and have nothing to do with the animal’s subjectivity directly: “given a variety of bivalves to eat, an octopus will match its bivalve-opening strategy to the force required to separate the shells of the bivalve” and “shown an image of itself, a cuttlefish will show agonistic behavior”. What might appear to be the inference of conscious processes is actually a speculation as to the possibility of some sort of conscious processes, which may never become more developed because of the inaccessibility of others’ subjectivities.

      That said, if we don’t assume away problems like the one you brought up, or for example, the classical problem of other minds, we have no chance of studying consciousness as a mechanism of behavior (by which I mean something like “understand the neural events which coincide with conscious states as a mechanism of behavior”.) These assumptions are less problematic if we treat science as an inquiry into function rather than an inquiry into truth, so that probabilistic predictive ability (which can be shown and discussed rather unambiguously) is our goal rather than “knowing” the Other (the Other being whatever behaving organism we’re studying.)

      I hope that makes sense.

  5. Govinda Dickman says:

    my way of saying: love the blog!!!

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  7. david says:

    I used to have trouble with the mirror test as a sign of awareness. My dogs used to see themselves in the mirror and would react at first. Eventually they would go sniff the image and after awhile just ignore it. I suggest animals are aware of themselves in terms of their primary senses and their normal environment. I also suggest their awareness is related to how other animals react to them. After all they seem to breed ok and try to evade being eaten.

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