What Scientists Know About Consciousness In Octopuses, Which Have 9 Brains

San Diego, California:

We named him Squirt – not because he was the smallest of the 16 cuttlefish in the pool, but because anyone with the audacity to scoop him into a separate tank to study him was likely to get soaked. Squirt had notoriously accurate aim.

As a comparative psychologist, I’m used to assaults from my experimental subjects. I’ve been stung by bees, pinched by crayfish and battered by indignant pigeons. But, somehow, with Squirt it felt different. As he eyed us with his W-shaped pupils, he seemed clearly to be plotting against us.

A brown and white invertebrate swims over rocks and seaweed. — A common cuttlefish (*Sepia officinalis*) in Portugal’s Arrábida Natural Park.
Diego Delso/Wikipedia, CC BY-SA

Of course, I’m being anthropomorphic. Science does not yet have the tools to confirm whether cuttlefish have emotional states, or whether they are capable of conscious experience, much less sinister plots. But there’s undeniably something special about cephalopods – the class of ocean-dwelling invertebrates that includes cuttlefish, squid and octopus.

As researchers learn more about cehpalopods’ cognitive skills, there are calls to treat them in ways better aligned with their level of intelligence. California and Washington state both approved bans on octopus farming in 2024. Hawaii is considering similar action, and a ban on farming octopus or importing farmed octopus meat has been introduced in Congress. A planned octopus farm in Spain’s Canary Islands is attracting opposition from scientists and animal welfare advocates.

Critics offer many arguments against raising octopuses for food, including possible releases of waste, antibiotics or pathogens from aquaculture facilities. But as a psychologist, I see intelligence as the most intriguing part of the equation. Just how smart are cephalopods, really? After all, it’s legal to farm chickens and cows. Is an octopus smarter than, say, a turkey?

A bright orange octopus attached to the arm of an underwater research vehicle. — A deepwater octopus investigates the port manipulator arm of the ALVIN submersible research vessel.
NOAA, CC BY

A big, diverse group

Cephalopods are a broad class of mollusks that includes the coleoids – cuttlefish, octopus and squid – as well as the chambered nautilus. Coleoids range in size from adult squid only a few millimeters long (Idiosepius) to the largest living invertebrates, the giant squid (Architeuthis) and colossal squid (Mesonychoteuthis) which can grow to over 40 feet in length and weigh over 1,000 pounds.

Some of these species live alone in the nearly featureless darkness of the deep ocean; others live socially on active, sunny coral reefs. Many are skilled hunters, but some feed passively on floating debris. Because of this enormous diversity, the size and complexity of cephalopod brains and behaviors also varies tremendously.

Almost everything that’s known about cephalopod cognition comes from intensive study of just a few species. When considering the welfare of a designated species of captive octopus, it’s important to be careful about using data collected from a distant evolutionary relative.

Marine biologist Roger Hanlon explains the distributed structure of cephalopod brains and how they use that neural power.

Can we even measure alien intelligence?

Intelligence is fiendishly hard to define and measure, even in humans. The challenge grows exponentially in studying animals with sensory, motivational and problem-solving skills that differ profoundly from ours.

Historically, researchers have tended to focus on whether animals think like humans, ignoring the abilities that animals may have that humans lack. To avoid this problem, scientists have tried to find more objective measures of cognitive abilities.

One option is a relative measure of brain to body size. The best-studied species of octopus, Octopus vulgaris, has about 500 million neurons; that’s relatively large for its small body size and similar to a starling, rabbit or turkey.

More accurate measures may include the size, neuron count or surface area of specific brain structures thought to be important for learning. While this is useful in mammals, the nervous system of an octopus is built completely differently.

Over half of the neurons in Octopus vulgaris, about 300 million, are not in the brain at all, but distributed in “mini-brains,” or ganglia, in the arms. Within the central brain, most of the remaining neurons are dedicated to visual processing, leaving less than a quarter of its neurons for other processes such as learning and memory.

In other species of octopus, the general structure is similar, but complexity varies. Wrinkles and folds in the brain increase its surface area and may enhance neural connections and communication.

Some species of octopus, particularly those found in reef habitats, have more complex brain structures compared to those living in the deep sea. This suggests that these species may exhibit higher levels of intelligence. Please refer to the original article for more information on octopuses and their relatives as a new animal welfare frontier. The article discusses what scientists know about consciousness in these unique creatures. This story has not been edited by NDTV staff and is published from a syndicated feed.