Out on a limb? On multiple cognitive systems within the octopus nervous system

ABSTRACT

The idea that there can be only one cognitive system within any single given cognitive organism is an established albeit implicit one within cognitive science and related studies of the mind. The firm foothold of this notion is due largely to the immense corpus of empirical evidence for the correlation of a high level of cognitive sophistication with a centralized nervous system. However, it must be pointed out that these findings are sourced in large part from studies on vertebrates. This paper presents a potential counterexample to the notion that only one cognitive system can be realized within any single genuine cognitive organism. This counterexample is the octopus, an invertebrate with what initially appears to be a paradoxical combination of vertebrate-like cognitive and behavioral capacities and a functionally decentralized nervous system. The extensive relegation of sensorimotor processing and control responsibilities to the peripheral nervous system which controls the arms of the octopus raises principled reasons to believe that the octopus is an organism that may house multiple independent cognitive systems.

KEYWORDS:

• Multiple cognitive systems
• dynamical cognition
• octopus cognition

Acknowledgement

The author is grateful to Emily C. Parke, Matthew Egbert, Glenn Carruthers, Ivan Gonzalez-Cabrera, Sam Woolley, and the anonymous reviewers of this paper for their comments and feedback.

Disclosure statement

No potential conflict of interest was reported by the author.

Notes

1. The appendages of the octopus are referred to as arms, not tentacles. Tentacles, which are found in squid and cuttlefish but not in octopuses, are anatomically and functionally distinct from arms. Arms have suckers all along their length, while tentacles only have them at the ends. Tentacles are used mainly for capturing prey, whereas arms are used for a variety of purposes (including prey capture).

2. As such, it can be argued that the capacity to self-initiate cognitive processing is a defining feature of an independent cognitive system. However, this issue requires considerable attention, and it is beyond the scope of this paper.

3. The split-brain syndrome, which affects some individuals who have undergone surgeries that involve partially or fully severing the corpus callosum (the fibers connecting the hemispheres of the brain), is the poster child of such a view, and it has motivated robust philosophical and empirical discussions. As it is characterized by conflicting behaviors performed simultaneously by the same person, the split-brain syndrome suggests the presence of multiple cognitive systems within a single individual (Bayne, 2010; Nagel, 1971; O’Brien & Opie, 1998; Sperry, 1968). Nevertheless, this particular conclusion remains the minority. Furthermore, the split-brain syndrome and other cases which suggest that an organism houses more than one cognitive system are considered nonneurotypicor even pathological (Thanks to Ivan Gonzalez-Cabrerafor pointing this out).

4. Thanks to Matthew Egbert for pointing out that, in robotics, the problem of coordinating and integrating the operations of multiple independent control systems – or even subsystems – within a single unit is so well-attested that it is considered a “non-problem,” or a given.

5. Robots with decentralized control architectures, such as Rodney Brooks’ “Creatures” (Brooks, 1991), usually have a behavioral repertoire that is limited and confined to simple tasks, as this is all they can manage to achieve without the system collapsing. Complex behavior requires extensive integration of information and coordination of motor output, which are extremely challenging to achieve without a centralized processing and control framework.

6. The split-brain syndrome is sometimes regarded as a “mild” form of having two cognitive systems present. When made to look at a compound word, “key-ring,” in such a way that the left eye can see only “key” while the right eye can see only “ring,” patients say that all they can see is “ring.” However, when asked to reach with the left hand for the item corresponding to the word that they say that they see, they reach for a key and not a ring (both are put in front of them). These phenomena are due to incomplete integration of visual and motor information. It thus appears that split-brain patients have two distinct sensorimotor nexuses, one for each side of the body.

Additional information

Notes on contributors

Sidney Carls-Diamante

Sidney Carls-Diamante is a postdoctoral research fellow at theKonrad Lorenz Institute for Evolution and Cognition Research.