Chapter 1 THE HABIT LOOP How Habits Work I. In the fall of 1993, a man who would upend much of what we know about habits walked into a laboratory in San Diego for a scheduled appointment. He was elderly, a shade over six feet tall, and neatly dressed in a blue button-down shirt. His thick white hair would have inspired envy at any fiftieth high school reunion. Arthritis caused him to limp slightly as he paced the laboratory''s hallways, and he held his wife''s hand, walking slowly, as if unsure about what each new step would bring. About a year earlier, Eugene Pauly, or "E.P." as he would come to be known in medical literature, had been at home in Playa del Rey, preparing for dinner, when his wife mentioned that their son, Michael, was coming over.
"Who''s Michael?" Eugene asked. "Your child," said his wife, Beverly. "You know, the one we raised?" Eugene looked at her blankly. "Who is that?" he asked. The next day, Eugene started vomiting and writhing with stomach cramps. Within twenty-four hours, his dehydration was so pronounced that a panicked Beverly took him to the emergency room. His temperature started rising, hitting 105 degrees as he sweated a yellow halo of perspiration onto the hospital''s sheets. He became delirious, then violent, yelling and pushing when nurses tried to insert an IV into his arm.
Only after sedation was a physician able to slide a long needle between two vertebra in the small of his back and extract a few drops of cerebrospinal fluid. The doctor performing the procedure sensed trouble immediately. The fluid surrounding the brain and spinal nerves is a barrier against infection and injury. In healthy individuals, it is clear and quick flowing, moving with an almost silky rush through a needle. The sample from Eugene''s spine was cloudy and dripped out sluggishly, as if filled with microscopic grit. When the results came back from the laboratory, Eugene''s physicians learned why he was ill: He was suffering from viral encephalitis, a relatively common disease that produces cold sores, fever blisters, and mild infections on the skin. In rare cases, however, the virus can make its way into the brain, inflicting catastrophic damage as it chews through the delicate folds of tissue where our thoughts, dreams-and according to some, souls- reside. Eugene''s doctors told Beverly there was nothing they could do to counter the damage already done, but a large dose of antiviral drugs might prevent it from spreading.
Eugene slipped into a coma and for ten days was close to death. Gradually, as the drugs fought the disease, his fever receded and the virus disappeared. When he finally awoke, he was weak and disoriented and couldn''t swallow properly. He couldn''t form sentences and would sometimes gasp, as if he had momentarily forgotten how to breathe. But he was alive. Eventually, Eugene was well enough for a battery of tests. The doctors were amazed to find that his body-including his nervous system- appeared largely unscathed. He could move his limbs and was responsive to noise and light.
Scans of his head, though, revealed ominous shadows near the center of his brain. The virus had destroyed an oval of tissue close to where his cranium and spinal column met. "He might not be the person you remember," one doctor warned Beverly. "You need to be ready if your husband is gone." Eugene was moved to a different wing of the hospital. Within a week, he was swallowing easily. Another week, and he started talking normally, asking for Jell-O and salt, flipping through television channels and complaining about boring soap operas. By the time he was discharged to a rehabilitation center five weeks later, Eugene was walking down hallways and offering nurses unsolicited advice about their weekend plans.
"I don''t think I''ve ever seen anyone come back like this," a doctor told Beverly. "I don''t want to raise your hopes, but this is amazing." Beverly, however, remained concerned. In the rehab hospital it became clear that the disease had changed her husband in unsettling ways. Eugene couldn''t remember which day of the week it was, for instance, or the names of his doctors and nurses, no matter how many times they introduced themselves. "Why do they keep asking me all these questions?" he asked Beverly one day after a physician left his room. When he finally returned home, things got even stranger. Eugene didn''t seem to remember their friends.
He had trouble following conversations. Some mornings, he would get out of bed, walk into the kitchen, cook himself bacon and eggs, then climb back under the covers and turn on the radio. Forty minutes later, he would do the same thing: get up, cook bacon and eggs, climb back into bed, and fiddle with the radio. Then he would do it again. Alarmed, Beverly reached out to specialists, including a researcher at the University of California, San Diego, who specialized in memory loss. Which is how, on a sunny fall day, Beverly and Eugene found themselves in a nondescript building on the university''s campus, holding hands as they walked slowly down a hallway. They were shown into a small exam room. Eugene began chatting with a young woman who was using a computer.
"Having been in electronics over the years, I''m amazed at all this," he said, gesturing at the machine she was typing on. "When I was younger, that thing would have been in a couple of six-foot racks and taken up this whole room." The woman continued pecking at the keyboard. Eugene chuckled. "That is incredible," he said. "All those printed circuits and diodes and triodes. When I was in electronics, there would have been a couple of six-foot racks holding that thing." A scientist entered the room and introduced himself.
He asked Eugene how old he was. "Oh, let''s see, fifty-nine or sixty?" Eugene replied. He was seventy- one years old. The scientist started typing on the computer. Eugene smiled and pointed at it. "That is really something," he said. "You know, when I was in electronics there would have been a couple of six-foot racks holding that thing!" The scientist was fifty-two-year-old Larry Squire, a professor who had spent the past three decades studying the neuroanatomy of memory. His specialty was exploring how the brain stores events.
His work with Eugene, however, would soon open a new world to him and hundreds of other researchers who have reshaped our understanding of how habits function. Squire''s studies would show that even someone who can''t remember his own age or almost anything else can develop habits that seem inconceivably complex-until you realize that everyone relies on similar neurological processes every day. His and others'' research would help reveal the subconscious mechanisms that impact the countless choices that seem as if they''re the products of well- reasoned thought, but actually are influenced by urges most of us barely recognize or understand. By the time Squire met Eugene, he had already been studying images of his brain for weeks. The scans indicated that almost all the damage within Eugene''s skull was limited to a five-centimeter area near the center of his head. The virus had almost entirely destroyed his medial temporal lobe, a sliver of cells which scientists suspected was responsible for all sorts of cognitive tasks such as recall of the past and the regulation of some emotions. The completeness of the destruction didn''t surprise Squire-viral encephalitis consumes tissue with a ruthless, almost surgical, precision. What shocked him was how familiar the images seemed.
Thirty years earlier, as a PhD student at MIT, Squire had worked alongside a group studying a man known as "H.M.," one of the most famous patients in medical history. When H.M.-his real name was Henry Molaison, but scientists shrouded his identity throughout his life-was seven years old, he was hit by a bicycle and landed hard on his head. Soon afterward, he developed seizures and started blacking out. At sixteen, he had his first grand mal seizure, the kind that affects the entire brain; soon, he was losing consciousness up to ten times a day.
By the time he turned twenty-seven, H.M. was desperate. Anticonvulsive drugs hadn''t helped. He was smart, but couldn''t hold a job. He still lived with his parents. H.M.
wanted a normal existence. So he sought help from a physician whose tolerance for experimentation outweighed his fear of malpractice. Studies had suggested that an area of the brain called the hippocampus might play a role in seizures. When the doctor proposed cutting into H.M.''s head, lifting up the front portion of his brain, and, with a small straw, sucking out the hippocampus and some surrounding tissue from the interior of his skull, H.M. gave his consent.
The surgery occurred in 1953, and as H.M. healed, his seizures slowed. Almost immediately, however, it became clear that his brain had been radically altered. H.M. knew his name and that his mother was from Ireland. He could remember the 1929 stock market crash and news reports about the invasion of Normandy.
But almost everything that came afterward-all the memories, experiences, and struggles from most of the decade before his surgery-had been erased. When a doctor began testing H.M.''s memory by showing him playing cards and lists of numbers, he discovered that H.M. couldn''t retain any new information for more than twenty seconds or so. From the day of his surgery until his death in 2008, every person H.M.
met, every song he heard, every room he entered, was a completely fresh experience. His brain was frozen in time. Each day, he was befuddled by the fact that someone cou.