Fascinating! From the New York Times:

Some scientific studies seem to support that such fingerprints exist. But many of those studies disagree on what the fingerprints are, and a multitude of other studies indicate there are no such fingerprints.

Let’s start with neuroscience. The Interdisciplinary Affective Science Laboratory (which I direct) collectively analyzed brain-imaging studies published from 1990 to 2011 that examined fear, sadness, anger, disgust and happiness. We divided the human brain virtually into tiny cubes, like 3-D pixels, and computed the probability that studies of each emotion found an increase in activation in each cube.
Overall, we found that no brain region was dedicated to any single emotion. We also found that every alleged “emotion” region of the brain increased its activity during nonemotional thoughts and perceptions as well.
The most well-known “emotion” region of the brain is the amygdala, a group of nuclei found deep within the temporal lobes. Since 2009, at least 30 articles in the popular press have claimed that fear is caused by neurons firing in the amygdala. Yet only a quarter of the experiments that we analyzed showed an increase in activity in the amygdala during the experience of fear. Indeed, it has long been known that certain “fear” behaviors, such as fleeing, don’t require the amygdala.
Other evidence against the amygdala-fear relationship comes from a pair of identical twins, known in the scientific literature as “BG” and “AM,” who both have a genetic disease that obliterates the amygdala. BG has difficulty feeling fear in all but the most extreme situations, but AM leads a normal emotional life.
Brain regions like the amygdala are certainly important to emotion, but they are neither necessary nor sufficient for it. In general, the workings of the brain are not one-to-one, whereby a given region has a distinct psychological purpose. Instead, a single brain area like the amygdala participates in many different mental events, and many different brain areas are capable of producing the same outcome. Emotions like fear and anger, my lab has found, are constructed by multipurpose brain networks that work together.
If emotions are not distinct neural entities, perhaps they have a distinct bodily pattern — heart rate, respiration, perspiration, temperature and so on?
Again, the answer is no. My lab analyzed over 200 published studies, covering nearly 22,000 test subjects, and found no consistent and specific fingerprints in the body for any emotion. Instead, the body acts in diverse ways that are tied to the situation. Even a rat facing a threat (say, the odor of a cat) will flee, freeze or fight depending on its surrounding context.
The same goes for the human face. Many scientists assume that the face clearly and reliably broadcasts emotion (scowling in anger, pouting in sadness, widening the eyes in fear, wrinkling the nose in disgust). But a growing body of evidence suggests that this is not the case. When we place electrodes on a human face and actually measure muscle movements during anger, for example, we find that people make a wide variety of movements, not just the stereotypical scowl.
CHARLES DARWIN famously vanquished the notion of essences in biology. He observed that a species is not a single type of being with a fixed set of attributes, but rather a population of richly varied individuals, each of which is better or worse suited to its environment.
Analogously, emotion words like “anger,” “happiness” and “fear” each name a population of diverse biological states that vary depending on the context. When you’re angry with your co-worker, sometimes your heart rate will increase, other times it will decrease and still other times it will stay the same. You might scowl, or you might smile as you plot your revenge. You might shout or be silent. Variation is the norm.
This insight is not just academic. When medical researchers ask, “What is the link between anger and cancer?” as if there is a single thing called “anger” in the body, they are in the grip of this error. When airport security officers are trained on the assumption that facial and body movements are reliable indicators of innermost feelings, taxpayers’ money is wasted.
The ease with which we experience emotions, and the effortlessness with which we see emotions in others, doesn’t mean that each emotion has a distinct pattern in the face, body or brain. Instead of asking where emotions are or what bodily patterns define them, we would do better to abandon such essentialism and ask the more revealing question, “How does the brain construct these incredible experiences?”
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