Dr. Frankenstein was up late one night, working on his monster project. He popped open the monster’s skull, attached electrodes to the brain in a random spot, and zapped it with electric current. The monster’s leg gave a little kick. “Hmm,” said Dr. Frankenstein. “Those neurons appear to control a kicking reflex.”
The good doctor moved the electrodes and delivered another jolt. This time, the monster’s pinkies wiggled. “Interesting,” remarked Dr. Frankenstein. “Circuitry for finger movement. Perhaps my monster will be capable of playing the piano.”
Finally, he placed the electrodes in a third spot and applied the current. This time, the corners of the monster’s mouth curled upward. “Eureka!” cried Dr. Frankenstein. “I’ve discovered the brain circuit for happiness!”
What just happened here? Dr. Frankenstein observed three different bodily motions in response to his electrical probe. He perceived the first two as simple actions but the third one as emotional. That’s because in his culture, an upturned mouth (i.e., a smile) has a meaning to communicate happiness.
In my book How Emotions are Made: The Secret Life of the Brain, I present evidence that the brain has no circuitry dedicated to any specific emotion, such as happiness, despite what Dr. Frankenstein might think. Plenty of other scientists, however, have claimed to locate distinct brain circuits for individual emotions, even in animals as diverse as monkeys, rats, crayfish, and flies. If that’s the case, how can there be no brain circuits for emotion?
The solution is simple but not obvious. Scientists who claim to find circuits for emotion in animal brains are doing what Dr. Frankenstein did. They’re discovering circuits for actions — running, teeth-baring, freezing in place, and so forth. But instead of recognizing these actions as collections of movements, the scientists perceive them as emotional, and write about them as emotional. Objectively speaking, these actions have no inherent emotional meaning. Freezing does not equal fear. Teeth-baring does not equal anger.
I call this error the mental inference fallacy. It means mistaking an action for an emotion in a scientific setting.
An action like smiling is a coordinated collection of movements. An emotion such as happiness is much more complex. It might involve smiling or it might not. It could involve other actions such as jumping, fist-bumping, crying, or even standing still with eyes closed. In addition, your culture has rules about when happiness is appropriate and when it isn’t. In short, you have many diverse concepts relating to happiness: its meaning, its causes, and its consequences. In the blink of an eye, your brain applies these concepts to construct meaning from the actions of others.
In exactly the same manner, scientists automatically and unconsciously construct emotional meaning from the actions of their lab animals. That’s the mental inference fallacy. It happens every time scientists record a physical measurement and assign it a mental cause. “That growl is expressing anger.” “That change in heartbeat was caused by excitement.” “That brain activity was caused by disgust.” I’m not saying that animal actions are meaningless. I’m saying that it’s a scientific pitfall to presume that an action has emotional meaning.
In the world of animal research, mental inference is rampant. For example, baby rats, when separated from their mother after birth, make a high-pitched noise that sounds to us like crying. Some scientists inferred that the brain circuitry responsible for the crying must be the circuitry for distress. But these baby rats aren’t sad. They’re cold. The sound is just a byproduct as the baby rats try to regulate their body temperature — a task normally done by their absent mothers. It has nothing to do with emotion. But to an observer, even a well-meaning and highly intelligent one, the sound is easily and automatically perceived as sadness.
Mental inference is normal. Children assign fascinating personalities to their toys. Adults do likewise with their cars. People constantly guess at the meanings of each other’s actions, from raised eyebrows to teenage eye rolls. But scientists in the lab must resist the lure of mental inference, lest they fall prey to the mental inference fallacy and unknowingly taint their research.
To be clear, I’m not saying here that animals cannot experience emotion (a topic that I discuss in much more detail in my book). I’m just saying that mental inference is automatic (in most cultures), and scientists frequently overlook its powerful effects.
So, the next time that you read about emotions being discovered in animals (or in monsters), watch for this pattern. If a scientist labels a action such as freezing using an emotion word like “fear,” you should think, “Aha, the mental inference fallacy strikes again!”