An Intelligence Divided - Do Octopuses Have 9 Brains?

How do we assess the intelligence of other species? One way is to search for certain skills and abilities, such as the use of a tool or the modification of an environment. However, the determination of whether an animal is considered proficient at these tasks is often subjective.

And, we need to acknowledge the anthropocentric selection of the behaviors that we consider to be signs of intelligence. Another measure commonly used is brain-to-body mass ratio, though this measure has issues as well— it would predict some rodents and birds to be more intelligent than humans, and few of us would like to believe this assessment. We can adjust depending on the specific animal groups we are trying to evaluate, but it’s still problematic.

Photo credit Janayara Machado — *Photo credit* *Janayara Machado*

For instance, octopuses defy the norm and reshape how we view intelligence in the natural world. This is not to say that octopuses lack an impressive brain—just the opposite. Overall, they boast 500 million neurons. For comparison, common garden snails, a molluscan relative, have only 10,000, and humanity’s best friend the dog just barely beats them at 600 million. Their actual brain, however, contains a minority of their neurons, while much of their leftover processing power is distributed throughout their arms, which contain more than two thirds of their total nerve cells. So, what all does this mean?

We have come to find out that although octopuses do have a central brain, they do not have a central mind, per se. In fact, when an octopus arm is detached from its body, it will still engage in seemingly purposeful behaviors… no, really. Even though the arm is no longer attached to a brain, it will continue responding to stimuli, recoil from pain, and even guide food to where its mouth used to be. Perhaps this is how an octopus knows how to control not only its arms and their complex movements, but also its skin color and all the other complex behaviors their otherworldly anatomy permits.

This division of intelligence has been proposed by many as a means of furthering AI (artificial intelligence)— something that humans may ultimately prove too single-minded to understand.

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