the rapid breathing. In other words, action precedes consciousness. We are afraid because we run. To illustrate, he asked his readers to imagine an encounter with a bear: When we see a bear, we don’t fear it and then run. We see it, run, and fear it—in that order. 2
It would take more than a century for this insight to be confirmed in the laboratory, where Joseph LeDoux, a neuroscientist at New York University, mapped the circuitry of fear in lab rats, tracing it to the amygdala, an almond-shaped organ buried deep in the temporal lobe of the brain. LeDoux didn’t go looking for the amygdala; he was looking for whatever region in the rat’s auditory system was required for fear conditioning. He began his search by pairing a tone with an electric shock—a paradigm that has shaped the course of science experiments ever since Ivan Pavlov trained dogs to salivate at the sound of a bell. Once the rats were conditioned to associate the two, LeDoux dropped the shock and just sounded the tone. Again, classic: The rats froze in place the instant they heard the sound. It was their learned response to a tone that signaled danger.
Now LeDoux began cutting into the rodents’ auditory cortex—the part of the auditory pathway associated with higher, rational thinking. The animals still froze whenever hesounded the tone; they were now terrified of a nonexistent electric shock and a noise they no longer consciously heard. LeDoux recognized that the auditory information must have split in the thalamus, a region in the lower brain that acts as a switching center for virtually all sensory information. But then what? Clearly, it traveled to some other part of the rat’s brain, a part of the subconscious that could still process the tone. To find where, he injected a tracer chemical into the thalamus and waited for it to piggyback on molecules traveling onward to the mysterious terminus. When he dissected the rat’s brain the next day, he laid it out under a microscope and found a stain of bright orange particles with streams and speckles against a dark blue-gray background. It was, he wrote, “like looking into a strange world of inner space. It was incredibly beautiful and I stayed glued to the microscope for hours.” 3
The stain had traveled to four regions of the brain. He resumed his cutting into the rats’ brains, sounding the tone, cutting, and sounding the tone once again, until, by the process of elimination, he hit pay dirt: the amygdala. “We do not tremble because we are afraid or cry because we feel sad,” LeDoux wrote, echoing William James. “We are afraid because we tremble and sad because we cry.”
Without an amygdala, a rat loses all fear. In some experiments, amygdala-less rats (ones whose amygdalae have been surgically removed) happily clamber on top of sleeping cats and nip at their ears. A person whose amygdala is damaged can’t recognize the expression of fear on another person’s face.
The amygdala leaps into overdrive whenever we feel threatened. It is our internal guard dog, always on the lookoutfor a moving shadow, a slammed gate, a knock at the door. When an engine backfires on the street, the amygdala receives the information and makes us jump, ready to fight or flee, before the prefrontal cortex (the conscious brain) weighs in. The whole process takes twelve milliseconds, during which the amygdala waits around—like a brilliant math student marking time while her more ordinary classmates catch up—for the higher brain to run its processing and figure out if there’s a problem.
Fear conditioning is not only lightning fast; it is the most effective learning. There is little forgetting when it comes to fear. That has been understood and even exploited for hundreds of years, as psychologist James McGaugh details in his 2003 book, Memory and Emotion :
“In medieval times, before writing was used to keep historical records, other means had to be found to maintain records of important events,
It would take more than a century for this insight to be confirmed in the laboratory, where Joseph LeDoux, a neuroscientist at New York University, mapped the circuitry of fear in lab rats, tracing it to the amygdala, an almond-shaped organ buried deep in the temporal lobe of the brain. LeDoux didn’t go looking for the amygdala; he was looking for whatever region in the rat’s auditory system was required for fear conditioning. He began his search by pairing a tone with an electric shock—a paradigm that has shaped the course of science experiments ever since Ivan Pavlov trained dogs to salivate at the sound of a bell. Once the rats were conditioned to associate the two, LeDoux dropped the shock and just sounded the tone. Again, classic: The rats froze in place the instant they heard the sound. It was their learned response to a tone that signaled danger.
Now LeDoux began cutting into the rodents’ auditory cortex—the part of the auditory pathway associated with higher, rational thinking. The animals still froze whenever hesounded the tone; they were now terrified of a nonexistent electric shock and a noise they no longer consciously heard. LeDoux recognized that the auditory information must have split in the thalamus, a region in the lower brain that acts as a switching center for virtually all sensory information. But then what? Clearly, it traveled to some other part of the rat’s brain, a part of the subconscious that could still process the tone. To find where, he injected a tracer chemical into the thalamus and waited for it to piggyback on molecules traveling onward to the mysterious terminus. When he dissected the rat’s brain the next day, he laid it out under a microscope and found a stain of bright orange particles with streams and speckles against a dark blue-gray background. It was, he wrote, “like looking into a strange world of inner space. It was incredibly beautiful and I stayed glued to the microscope for hours.” 3
The stain had traveled to four regions of the brain. He resumed his cutting into the rats’ brains, sounding the tone, cutting, and sounding the tone once again, until, by the process of elimination, he hit pay dirt: the amygdala. “We do not tremble because we are afraid or cry because we feel sad,” LeDoux wrote, echoing William James. “We are afraid because we tremble and sad because we cry.”
Without an amygdala, a rat loses all fear. In some experiments, amygdala-less rats (ones whose amygdalae have been surgically removed) happily clamber on top of sleeping cats and nip at their ears. A person whose amygdala is damaged can’t recognize the expression of fear on another person’s face.
The amygdala leaps into overdrive whenever we feel threatened. It is our internal guard dog, always on the lookoutfor a moving shadow, a slammed gate, a knock at the door. When an engine backfires on the street, the amygdala receives the information and makes us jump, ready to fight or flee, before the prefrontal cortex (the conscious brain) weighs in. The whole process takes twelve milliseconds, during which the amygdala waits around—like a brilliant math student marking time while her more ordinary classmates catch up—for the higher brain to run its processing and figure out if there’s a problem.
Fear conditioning is not only lightning fast; it is the most effective learning. There is little forgetting when it comes to fear. That has been understood and even exploited for hundreds of years, as psychologist James McGaugh details in his 2003 book, Memory and Emotion :
“In medieval times, before writing was used to keep historical records, other means had to be found to maintain records of important events,
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