Receive emails about upcoming NOVA programs and related content, as well as featured reporting about current events through a science lens. Email Address Zip Code Subscribe With one of the largest brain-to-body size ratios of all the invertebrates, the inquisitive cuttlefish could teach us about the evolution of intelligence throughout the animal kingdom—even among humans. Photo credit: istockphoto.com/© Victor Maffe

CAPTIVATED BY CUTTLEFISH

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NOVA: When did you begin working with cuttlefish?

Jean Boal: I've been working with octopuses since 1988, but I didn't start researching cuttlefish until a few years later, in 1993. There are no cuttlefish in the Americas, so like most Americans I'd never heard of them. But I began work with cuttlefish because of an opportunity: I was working at the National Resource Center for Cephalopods, where they had a lot of cuttlefish, and I was interested in comparing different species of cephalopods and their behavior.

What makes cuttlefish so interesting?

Cuttlefish and all other cephalopods are clever and remarkable animals. I am frustrated when people compare them to mammals, because I think that's to misunderstand them. They have a totally different evolutionary history. Cephalopods are fast, and they're out there interacting with fish and marine mammals, doing really exciting things that fish and marine mammals don't do. And they're reacting quickly and solving problems, and I think that's really cool.

And they have that amazing color-changing ability, of course.

Yes. Cuttlefish have the most splendid body patterns—they're just mesmerizing. Most people, when they see the way the cuttlefish can change their body patterns, they're totally captivated. On top of that they have all kinds of cool social behavior that octopuses just don't have. I think once you see the body patterning and the social interactions in cuttlefish, you're captivated for life. They're really splendid.

With one of the largest brain-to-body size ratios of all the invertebrates, the inquisitive cuttlefish could teach us about the evolution of intelligence throughout the animal kingdom—even among humans. Photo credit: istockphoto.com/© Victor Maffe

So are cuttlefish social creatures? What role does their chameleon-like ability play in social situations?

They're not highly social the way we think about mammals being social. But they definitively have a lot of interactions with each other, particularly as adults. The males have all kinds of impressive displays that they use when interacting with each other, when they determine who is dominant. A cuttlefish can even simultaneously adjust one side of his body to show a dominant display toward other males, while the other side of his body shows a calm display towards a potential mate. It's really quite amazing.

I have a picture that I just love. It's a gravel bottom with bits of shells, and you can look at it for ages before you see all the tiny little cuttlefish that are there, blending into the background. It's just awesome, like one of those puzzles that you saw when you were a kid where you had to circle the hidden objects. They have a fantastic way of blending into the background.

One of Nature's masters of disguise, cuttlefish can change their skin pattern and texture in order to blend in with their surroundings. Here, a cuttlefish lurks on the seafloor. Photo credit: © NOVA/WGBH Educational Foundation

Octopuses have become a part of popular culture, but as you say, we in the Americas know very little about cuttlefish. How do these animals differ?

Octopuses love to destroy lab equipment [laughs]. If they can possibly rip something apart, they will. But more importantly, octopuses are solitary and are not good candidates for social learning, whereas cuttlefish have interesting social behavior. With cuttlefish, I can look at communication as a way of learning something about what they know about the world.

I think people think of octopuses as more clever for a couple of reasons. Again, in the United States few people know what cuttlefish are. Plus, much of the early research was done with octopuses, while early work on nervous systems was done with squid. Octopuses are unbelievably easy to anthropomorphize. They look at you and they interact with you and they reach out an arm to your finger—they're just so charismatic.

Cuttlefish are usually in a tank where you're looking down at them. You don't get a good chance to make eye contact, and they don't pick up things and manipulate them the way octopuses do. So they don't have that immediate kind of grab-at-you personality at first that an octopus does. But if you ever look at one eye-level, I think you get pretty caught up in cuttlefish, too.

OF MAZES, ODORS, AND SOUNDS

You test learning by creating mazes for your cephalopods. Could you describe these contraptions?

The octopus maze looks different than the cuttlefish maze, but it tries to get at the same question: could the cephalopod learn its way around a maze with two possible exits, one closed and one open? Octopuses won't go through the maze for us reliably and show us what they know unless we keep the water very shallow. But that's pretty stressful for them, so we're trying a new design that will be a little gentler on them.

The cuttlefish maze also incorporates two possible exits, and it has taught us a lot about these creatures. First off, we've found that they can learn to solve a maze like this—a maze where they first have to learn to go right and then later they have to learn to go left. And then once they've mastered that, they have to learn to go right, and once they've mastered that, go left—and they get faster and faster doing this.

This maze, used to test learning abilities in cuttlefish, incorporates visual cues the animals must follow in order to find the proper exit. Photo credit: © NOVA/WGBH Educational Foundation

This is called "serial reversal learning" or a "learning set." The concept is that one of these two doors is open, and if I, as a cuttlefish, say, just test one and it's closed, that means this period of time, it's the other one that's open. Some decades ago, researchers showed octopuses could learn that problem, and we were able to show that cuttlefish could also. This kind of conceptional learning, a complex way of learning, goes far beyond what you would see in snails or other kinds of animals cuttlefish are related to.

The ultimate question is, am I smart enough to find out how smart they are?

Are cuttlefish easier to work with than octopuses?

Cuttlefish are great to work with because they don't stick themselves to the bottoms of tanks like octopuses do. And you don't have to house them separately like you do with octopuses—you can put them together in one large tank, which is much easier for cleaning and maintenance and feeding and all that. In terms of their performance in experiments, octopuses are unbelievably erratic. One day they will be brilliant and for the next five days they'll act like they don't know anything at all. So it actually takes pretty intense statistics to figure out what they know and don't know. In the past, I've had more consistent performances from cuttlefish, although sometimes they like to be erratic, too. In general I've had an easier time interpreting their performances, and they are more consistent than octopuses are.

So are cuttlefish more "clever" than octopuses and other cephalopods?

I don't think it's fair to say that they are more or less clever than the other cephalopods. Based on my experience, I couldn't rank cuttlefish and octopuses, for example, with one being smarter than the other. I think one might be better at one task than the other, because of the way they learn and by the way the experiment is designed. I do find it more challenging to design experiments for octopuses in some ways than for cuttlefish. But for both animals, the ultimate question is, am I smart enough to find out how smart they are?

What other kinds of tests besides maze-learning are you conducting with your cuttlefish?

One of the big areas of my work right now is chemical communication. All of the cephalopods, it looks like, emit odors, if you will, through the water that travel to other animals of the same species and, we think, serve to coordinate reproductive behavior. We're working on figuring out what those chemicals are and how they use them.

I've also just finished up a piece of work on the perception of sound, or vibration in the water. Cuttlefish perceive that low-frequency vibration, and they respond in their behavior. So, we knew that their tissues, their physiology, their bodies could theoretically respond to such sounds. But we showed that it changes their behavior when they perceive such vibrations. So a lot of my work is about sensory systems and communication, in addition to learning.

An aptly named "flamboyant" cuttlefish puts on a brightly colored display, indicating to nearby divers that it is poisonous. Photo credit: © NOVA/WGBH Educational Foundation

LEARNING ABOUT LEARNING

In a broad sense, what are you hoping to find out through such work?

I'm interested in cephalopod learning and communication, communication as a sort of window into their minds. I'm really interested in why cephalopods have such large brains compared to their relatives, clams and snails. Cuttlefish are very engaging, and on top of that, it looks like their brain size relative to body size is perhaps the largest of the invertebrates, even larger than in octopuses. Cuttlefish ended up leading me into lots of interesting areas of behavior that I couldn't research with octopuses.

The research could give us some insights into human aging.

Why is it useful to understand cuttlefish intelligence? What are the implications?

I think all of us who are interested in learning and intelligence really want to know why intelligence evolves sometimes and not in other situations. What is it really good for? And probably every person would love to know why people are as smart as we are, so to answer that we really have to understand the situations in which intelligence has been favored by natural selection. If we just look at a group of animals that are closely related, that doesn't tell us enough about the ancient past, because all those animals have the same ancestors. If a chimpanzee is smart and a human is smart, is it because we had to be smart in our current lives or is it some ancestor to all of us a long time ago that had to be smart?

What's really exciting about cephalopod intelligence is, we know that their relatives are clams and snails. Those are not animals that had a need for great intelligence, so whatever happened to cephalopods was different. If we can figure out what they're using their intelligence for, that would tell us what these factors are in the environment that created need for intelligence. And that can shed some light on our own intelligence.

What else can cuttlefish tell us about ourselves?

There are some very exciting developmental studies with cuttlefish that show that they provide a good model of aging and learning as we get older. They're great models for that kind of thing because their whole life span is a single year, so we can study an individual animal throughout its life and see the whole trajectory without waiting years and years for data. So we can see, for example, how cuttlefish brain function changes with age, and we can observe this within the span of just weeks or months. The research could give us some insights into some of the problems involved in human aging, such as memory loss and slower learning abilities.

Where would you like to be in 10 years?

What I'd really like for myself in 10 years is to have come up with lots of clever ways that other people can go further with cephalopod learning research—so people can try to understand what cephalopods know, and so the data can benefit us all. For example, [it would be great] if my behavior studies were useful to people trying to understand about cephalopod sensory systems and my learning studies were useful for people who will then study their brains. If I can design, for example, clever ways of looking at how cephalopod nervous systems function in their behavior, then other scientists can use those tasks and go on with other investigations.

"[T]he cuttlefish might seem alien to us, but it could tell us more about ourselves than we realize," claims biologist and animal behaviorist Jean Boal. Photo credit: © Emily K. Reinauer

So, after nearly 20 years of working with these animals, what keeps you fascinated?

You know, when I started I was mostly fascinated by the cuttlefish and octopuses themselves. And now I think I am every bit as fascinated by people's response to them. I love working with the students and seeing how much they're drawn in, and how the public comes to visit my lab and sees the animals and is inspired to ask lots of questions. I think it's wonderful.