If you have never watched bees carefully, you are missing out. Look closely as they gently curl and uncoil their mouthparts around food, and you will sense that they are not just eating but enjoying their meal. Watch a bit more, and the hesitant flicks and sags of their antennae seem to convey some kind of emotion. Do those twitches signal annoyance? Or something like enthusiasm?
Whether bees really experience any of these emotions is an open scientific question. It is also an important one, with implications for how we should treat not just bees but the great majority of animals. Recently studies by Melissa Bateson and her colleagues at Newcastle University in England have rekindled the debate over these issues by showing that honeybees may experience something akin to moods.
Using simple behavioral tests, Bateson’s team showed that honeybees under stress tend to be pessimistic. Other tests have demonstrated that monkeys, dogs and starlings all tend to react similarly under duress and likewise see the proverbial glass as half empty. Although this finding does not—and cannot—prove that bees experience humanlike emotions, it does give pause. We should take seriously the possibility that insects, too, have emotions.
Beeline to the Brain
First, a little bit about bees. They are members of the diverse group of animals lacking backbones—indeed, more than 95 percent of all animal species are invertebrates. Despite the varied and often nuanced behaviors they can exhibit, invertebrates are sometimes regarded as life’s second string, a mindless and unfeeling band of alien critters. If that seems somewhat melodramatic, just consider our willingness to boil some of them alive.
Those judgments tend to arise from arguments about invertebrates’ failure to demonstrate the behaviors we usually associate with a pain response. Whereas the yelps and grimaces of other mammals are familiar to us as announcements of hurt, invertebrates can appear to take their injuries in stride. Insects are commonly observed using their crushed limbs with undiminished force when walking, for example, and a locust will reportedly carry on with a meal while it is being eaten by a mantis.
Other attempts to draw a dividing line between creatures that feel and those that do not are rooted in comparative brain anatomy. Invertebrates lack a cortex, an amygdala and many of the other major brain structures routinely implicated in human emotion. Their nervous systems are quite minimalist compared with ours: we have roughly 100,000 bee brains’ worth of neurons in our head. Some invertebrates, however, including insects, do possess a rudimentary version of our stress response system. So the question remains: Do they experience emotion in a way that we would recognize, or do they simply react to the world with an elaborate set of reflexes?
To gain some traction on this fascinating question, Bateson’s team followed the lead of recent investigations on “pessimistic biases” in animals. In humans, the pessimistic bias refers to our well-known tendency to perceive threats or anticipate negative outcomes more frequently when we are feeling anxious or depressed. For example, in tests where people are shown ambiguous statements such as “the doctor examined little Emily’s growth,” anxious individuals are less likely than others to conclude that Emily is fine and only her height was being checked.
Although the link between bad moods and negative judgments may not be terribly surprising, this correlation is still useful. We rely on it in our daily lives to make informed guesses about how people are feeling by observing their actions and choices. Scientifically, we can use it to study the emotions of creatures unable to tell us directly how they feel. The key here is to set up a controlled situation where animals encounter an ambiguous stimulus—think of it as a nonverbal version of the Emily statement.