Science Watch

Last summer, staff at the Seattle Aquarium discovered that their new octopus had a talent for mischief. When they came to feed her or clean her tank, she would blow water jets in their direction. After a few soakings, they settled on a name for her: Dolores Umbridge, a villain from the Harry Potter series.

Cute? Sure. But also telling. Seattle Aquarium biologist Roland Anderson, PhD, who has worked there for more than 30 years, noticed years ago that the staff only name a few types of animals: seals, sea otters and one cold-blooded species, the octopus.

"This general idea was what got us thinking about octopus personality," says Jennifer Mather, PhD, a comparative psychologist at the University of Lethbridge in Alberta, Canada.

Anderson and Mather are among a group of researchers finding that these animals have surprising brainpower and, controversially, what seems like personality.

All octopuses, along with cuttlefish and squid, are cephalopods. There are about 300 octopus species, ranging from the Giant Pacific Octopus, which can weigh 100 pounds and stretch its arms more than 15 feet, to the East Pacific Red Octopus, which weighs less than a quarter of a pound. These invertebrates evolved from shelled mollusks and split from the human evolutionary line 1.2 billion years ago, making them more closely related to hookworms than humans.

Studying animals that are so smart yet so far removed from us on the evolutionary tree can help us understand how thinking evolves--not human thinking in particular, but thinking in general, Mather says--by showing how a completely different set of evolutionary pressures might lead to advanced behavior.

Shy gals and gregarious guys

Over the past 20 years, comparative psychologists have been finding evidence of individual differences in temperament--traits such as aggression and sociability--in animals including hyenas, dogs and birds. Octopuses were the first invertebrates that researchers investigated for signs of what some are willing to call personality.

In 1986, Anderson wrote up an account of Dolores's Seattle Aquarium predecessors in the International Zoo Yearbook (Vol. 26, No. 1): Emily Dickinson, an octopus so shy she would squeeze her 25-pound body into a 3-inch space behind the backdrop of her tank; Emily's opposite, Leisure Suit Larry, whose arms were always "all over you;" and mischievous Lucretia McEvil, who ripped up the inside of her tank and blew water at her caretakers.

Several years later, in 1993, Mather and Anderson published a study that looked more carefully at these animals' individual differences. They gave 44 octopuses three tests--opening their tank lids, touching them with a brush, and feeding them crabs--and recorded the animals' responses to the tests, which they administered seven times over two weeks.

They found that the octopuses reacted differently to the stimuli. Some shrank from the brush while some ignored it, some grabbed the crab immediately while others waited for it to run by. But each octopus was consistent across time and task--those that were passive were almost always passive, those that came out to explore did so nearly every time.

In a follow-up study, then-graduate student David Sinn, PhD, found evidence that octopuses pass these traits on to their offspring. Sinn followed octopuses for the first nine weeks of their lives and found that animals that shared the same mother reacted to the tests more similarly than those that didn't, according to a 2001 paper published in the Journal of Comparative Psychology (Vol. 115, No. 4). Octopuses don't raise their young, so the babies hadn't learned from observing their mothers. Instead, the study raised the intriguing possibility that at least some aspects of octopus "personality" might be genetic.

However, Sinn also found that the animals' responses to the tests changed as they matured, suggesting that perhaps, as in humans, their personalities develop from a mixture of genetic and environmental influences.

Skinny arms, big brain

Octopuses may differ from one another in temperament, but they share an impressive level of intelligence. Studies have shown that they can learn and adapt new techniques for opening different types of their favorite prey (clams and mussels); that they can use cues to escape from mazes; and that they can learn to identify individual humans, among other abilities.

These skills are not unique in the animal kingdom, of course--rats can learn mazes, and chimpanzees, famously, use tools to find food. But evolutionarily speaking, octopuses are far removed from these mammals

"The point--what's interesting--is that there's this convergence," says researcher Jean Boal, PhD, of Millersville University in Pennsylvania. "We have completely different brains, organized differently, each evolved from its own line, yet we end up with some of these same skills."

In the clam study, published in 2007 in the Journal of Comparative Psychology (Vol. 121, No. 3), for example, Mather and Anderson found that octopuses use three techniques to open different types of shells: They simply break open fragile mussel shells, they pull apart stronger Manila clams with their arms and they use a tooth to drill into the very strong shells of littleneck clams. But when the researchers gave octopuses a super strong Manila clam--one sewn shut with metal wire--the octopuses weren't deterred, they simply switched their strategies and drilled into the Manila clam.

Octopuses also have impressive spatial memory. In one study, published in 2007 in Animal Cognition (Vol. 10, No. 4), Boal found that they could learn to use clues to discriminate between two different mazes. Boal alternately trained the octopuses on two mazes with different configurations. In each they had to travel directly from the center of a brightly lit tank to a small, dark burrow--an environment they preferred--while avoiding a false burrow that had been blocked by an upside-down clear glass jar. After five trials in each maze, they learned to recognize which maze they were in and immediately head for the correct burrow.

While there's no question that octopuses are smart, Boal notes that their reputation may benefit from our tendency to see humanlike traits in the animals.

"I think cephalopods are easy to anthropomorphize," she says, because they have expressive eyes and arms that function like hands.

An alien intelligence

Such concerns aside, octopuses do seem to be the most intelligent invertebrates around, and the research question that fascinates psychologists is how and why they evolved to be such effective problem-solvers.

Human and other primate intelligence is often attributed to the fact that we evolved to live in social groups and needed brainpower to navigate the complexity of interacting with others of our species. But octopuses are solitary animals that live their short lives--about one to two years--mostly alone.

Jennifer Mather thinks that the answer may lie in the complexity of the ocean environment that they deal with, which is populated with thousands of species. "Tropical coral reefs are hugely, hugely varied," she says, compared with environments on land. "Maybe the rainforest comes close, but that's all."

She and her colleagues, including Anderson, conducted a three-year study on the island of Bonaire, off the coast of Venezuela, in which she kept a record of octopuses' diets in the wild. She found that they ate more than 90 different species, including clams, conch and crabs--each of which required a different strategy to capture. Meanwhile, dozens of species were trying to eat the octopuses, and each required a different strategy to evade.

If you're an octopus, Mather says, "you'd better be smart, because there's a lot out there to eat and a lot that would like to eat you."

Octopus intelligence also seems to be uniquely suited to its environment. They learn quickly, but they have short memories for food location. If you teach them to find food at a particular site, Mather says, they'll go back to that site for a while, but they'll soon branch out and start exploring new sites instead. Other animals do this as well, but only when the supply of food at the first location has run out. Researchers aren't sure, but it seems possible that octopuses explore even when food remains in the original location. That makes sense, Mather says, because the crabs and clams octopuses hunt are not likely to inhabit the same place twice: "If there's a McDonald's on the corner, and I want that food, the McDonald's will be there tomorrow," she says. "But if an octopus finds a crab under a rock, there's no use going back to that rock tomorrow, because there won't be another one there."

Considering how octopuses evolved their smarts gives comparative psychologists a different perspective on intelligence, according to Mather. Most comparative psychologists study animals that are stops on the evolutionary chain that eventually led to humans--vertebrates, mammals, primates. But octopuses' brains and personalities illustrate another evolutionary route to intelligence.

And, Mather says, there is much left to learn about how far that intelligence stretches: "In psychology, we're used to knowing a lot about the animals we study. But as soon as you started poking around with cephalopods, you realize how little we still know."

Lea Winerman is a writer in Washington, D.C.