Octopus Arms Have a Mind of Their Own, Make Decisions

Long an inspiration for science-fictional, tentacled aliens from outer space, the octopus may be as alien an intelligence as we can meet on Earth, Sivitilli said. He believes understanding how the octopus perceives its world is as close as we can come to preparing to meet intelligent life beyond our planet.

“It’s an alternative model for intelligence,” Sivitilli said. “It gives us an understanding as to the diversity of cognition in the world, and perhaps the universe.”

The octopus exhibits many similar behaviors to vertebrates, like humans, but its nervous system architecture is fundamentally different, because it evolved after vertebrates and invertebrates parted evolutionary ways, more than 500 million years ago.

Vertebrates arranged their central nervous system in a cord up the backbone, leading to highly centralized processing in the brain. Cephalopods, like the octopus, evolved multiple concentrations of neurons called ganglia, arranged in a distributed network throughout the body. Some of these ganglia grew more dominant, evolving into a brain, but the underlying distributed architecture persists in the octopus’s arms, and throughout its body.

“The octopus’ arms have a neural ring that bypasses the brain, and so the arms can send information to each other without the brain being aware of it,” Sivitilli said. “So while the brain isn’t quite sure where the arms are in space, the arms know where each other are and this allows the arms to coordinate during actions like crawling locomotion.”

Of the octopus’ 500 million neurons, more than 350 million are in its eight arms. The arms need all that processing power to manage incoming sensory information, to move and to keep track of their position in space. Processing information in the arms allows the octopus to think and react faster, like parallel processors in computers.

Sivitilli works with the largest octopus in the world, the Giant Pacific octopus, as well as the smaller East Pacific red, or ruby, octopus. Both species are native to Puget Sound off Seattle’s coast and the Salish Sea, and have learning and problem-solving capabilities analogous to those studied in crows, parrots and primates.

To entertain the octopuses and study their movements, Sivitilli and his colleagues gave the octopuses interesting, new objects to investigate, like cinder blocks, textured rocks, Legos and elaborate mazes with food inside. His research group is looking for patterns that reveal how the octopus’ nervous system delegates among the arms as the animal approaches a task or reacts to new stimuli, looking for clues to which movements are directed by the brain and which are managed from the arms.

Sivitilli employed a camera and a computer program to observe the octopus as it explored objects in its tank and looked for food. The program quantifies movements of the arms, tracking how the arms work together in synchrony, suggesting direction from the brain, or asynchronously, suggesting independent decision-making in each appendage.

“You’re seeing a lot of little decisions being made by these distributed ganglia, just by watching the arm move, so one of the first things we’re doing is trying to break down what that movement actually looks like, from a computational perspective,” Gire said. “What we’re looking at, more than what’s been looked at in the past, is how sensory information is being integrated in this network while the animal is making complicated decisions.”
 
 

Contacts and sources:
Dominic Sivitilli / David Gire
American Geophysical Union

Citation: “Collective cognition in the arms of the octopus”
Dominic Michel Sivitilli, Department of Psychology and Astrobiology Program, University of Washington, Seattle, WA
David H Gire, University of Washington, Department of Psychology, University of Washington, Seattle, WA