Image: Wikimedia Commons/MikeMurphy
David Foster Wallace's "Consider the Lobster" was perhaps the first (or, at the very least, the most poignant) mainstream essay to rail against the idea of boiling animals alive before we eat them. Since then, researchers shown that lobsters feel pain. And, now, they've also shown that crustaceans feel anxiety in a way that's very similar to humans.
Most animals show some sort of stress response when they are threatened—but a study by French researchers published Thursday in Science is the first that shows invertebrates are capable of feeling true anxiety. That's important, because it suggests that invertebrates potentially feel "secondary emotions" that can occur long after a stimuli is applied.
"Sources of stress or danger provoke fear, a basic emotion, and generate immediate responses, such as escape, freezing, or aggression. Stress can also lead to anxiety, a more complex state that is considered a secondary emotion because it occurs when the stressor is absent or not clearly identified," said Pascal Fossat, lead author of the Science study.
Anxiety felt by crayfish, which Fossat studied, is similar to the anxiety felt in humans and other vertebrates, both neurologically and in practice—that is, crayfish seek out "safe" spaces and are less likely to be adventurous if they are feeling anxious.
In fact, anxiety in crayfish appears to be caused and controlled by serotonin, an important hormone that is believed to play an important role in human anxiety. And, how do you treat anxiety in crayfish? With benzodiazepines—the same way you do in humans.
To test his theory, Fossat designed a maze, with light, dark, and medium-light environments in it. Typically, crayfish prefer dark areas, but they're usually willing to venture into light ones. The maze was set up like this:
Normal, unstressed crayfish showed some hesitation before entering the well-lit areas of the tank, but generally entered them. Fossat then shocked a group of crayfish with electricity to stress them out. Even well after the shocking had ended, these crayfish had highly elevated serotonin levels and cowered in the dark corners of the tank, afraid to go into the light areas. After being injected with benzos, however, the crayfish became adventurous again.
"We demonstrate that stressed crayfish express context-independent anxiety-like behavior that can be promoted by [increased serotonin levels] and abolished by a benzodiazepine," he wrote.
To further prove that it was serotonin causing the anxiety, Fossat injected crayfish with serotonin—they displayed the same anxious behavior that the shocked crayfish displayed.
Foster Wallace wrote Consider the Lobster back in 2004, before we knew that crustaceans could feel pain, and before this latest finding about anxiety. Still, his intuition that lobsters don't exactly like being boiled alive appears to be irrefutable the more we learn about crustaceans.
"After all the abstract intellection, there remain the facts of the frantically clanking lid, the pathetic clinging to the edge of the pot. Standing at the stove, it is hard to deny in any meaningful way that this is a living creature experiencing pain and wishing to avoid/escape the painful experience," Foster Wallace wrote. "To my lay mind, the lobster’s behavior in the kettle appears to be the expression of a preference; and it may well be that an ability to form preferences is the decisive criterion for real suffering."
No, crayfish are not lobsters, but they're from the same order as lobsters (and we eat crayfish after boiling them live, too), and have been shown to have similar nervous systems. In fact, they may even be closer to humans than you might have expected. "Our results emphasize the ability of an invertebrate to exhibit a state that is similar to mammalian emotion," Fossat wrote.
Foster Wallace added that, in 2004, there was a "low-level cultural unease about the boiling thing." Perhaps this latest news will be the steam that brings that unease to a full heat.