How We Learn (9 page)

Those are contextual cues, when they’re conscious and visible. The reason I can recall them is that they’re also part of a scene, an autobiographical memory. The science tells us that, at least when it comes to retention of new facts, the subconscious ones are valuable, too. Not always—when we’re submerged in analytical work, they’re negligible—and not necessarily all of them. Only sometimes. So what, though? When it comes to learning, we’ll take any edge we can get.

I recall something else about that night, too. Normally, when visited by the Ghost of Physics Past, I was not entirely patient. I had work to do. I could do without the lecture about the properties of quartz. That night, though, I’d finished most of my studying and was in an open, expansive mood. I was happy to sit and listen and even hear about how “physics students today, they don’t learn any of this …”

That mood was part of my “environment,” too, wasn’t it? It had to be—I remember it. I wouldn’t have sat still for the lesson otherwise. If psychologists’ theory about reinstating sights and sounds was correct, then they’d have to show that it applied to internal mental states as well—to jealousy, anxiety, grumpiness, confidence—the entire mix-tape of emotions running through our heads.

The question was, how?

• • •

No one who’s gone through a bad breakup while trying to be a student will doubt the impact of mood on learning. Moods color everything we do, and when they’re extreme they can determine what we remember. The clearest demonstration comes from psychiatry, and the study of bipolar disorder. People with this condition are the extreme athletes of the emotional realm. Their moods cycle between weeks or months of buoyant, manic activity and periods of dark, paralyzing depression, and they know too well that those cycles determine what they remember and what they don’t. “There is a particular kind of pain, elation, loneliness, and terror involved in this kind of madness,” wrote the psychologist Kay Redfield Jamison, who has a diagnosis of bipolar. “When you’re high it’s tremendous. The ideas and feelings are fast and frequent like shooting stars, and you follow them until you find better and brighter ones.… But, somewhere, this changes. The fast ideas are far too fast, and there are far too many; overwhelming confusion replaces clarity.
Memory goes.”

Indeed, researchers showed in a 1974 study that people with bipolar disorder have state-dependent memory: They remember best what happened during manic phases when
they’re again manic. And vice versa: When depressed, they recall events and concepts they’d learned when they were down. As the study’s authors put it, “associations or episodic events … can be regenerated more completely in a similar mood state than they can in a different mood state.”

Yet bipolar is an extraordinary condition, and learning scientists could hardly rely on it to measure the effects of emotion on the rest of us. For most people, moods come and go, coloring our experience rather than defining it. Their impact on memory, if significant at all, would be far weaker than for those with bipolar. And to measure this impact in a rigorous way would mean inducing the same mood in groups of people, reliably and continuously. That’s a tall order, so learning scientists began to focus not on moods per se but on the influence of differing “internal mental states.” Altered states.

This was the 1970s, after all, when hundreds of thousands of
young people were experimenting with consciousness-altering drugs, primarily LSD and marijuana. These recreational users, many of them college students, weren’t interested in the effect of the drugs on their grades—they were enjoying themselves. Yet there were all sorts of rumors about the possible benefits of such substances on learning. Hallucinogens were said to be “mind-expanding,” capable of opening up new ways of thinking about the world. Pot allowed the brain to see connections it hadn’t before (often too many, resulting in late night sessions full of perfect nonsense). Clearly, altered states intensified experience; might they intensify memory?

The rigorous research into our inner study environment would begin with drugs—the recreational kind. And its primary sponsor was the U.S. government, which, beginning in the early 1970s, funded a string of experiments that might be called the Studying Under the Influence series. By then, a scattering of research reports had already appeared, suggesting that some drugs, like barbiturates and alcohol, could produce so-called state-dependent learning in modest amounts—the “Study Aid” effect. The government-backed researchers wanted to clarify the picture.

These experiments tended to follow a similar blueprint: Get people high and have them study something; then give them a test hours later—either after getting high again or after ingesting a placebo. We’ll take a close look at one of these studies, to show what serious scientists and serious stoners can do when they put their heads together. In 1975, a research team led by James Eric Eich of the National Institute of Mental Health set out to test the effect of pot on retention (word lists again), as well as learn something about
how
the drug alters what the brain does
with newly studied information. The researchers recruited thirty college students and recent graduates, brought them into their lab, and gave each a joint. Half of the group got a real one and half got a “placebo marijuana cigarette,” which looked and smelled real but delivered no THC, the active drug. “The subjects took deep inhalations, maintained them for 15 seconds, and
repeated this process every 60 seconds,” the authors wrote. “The entire cigarette was smoked, with the aid of a holder, usually in about eight minutes.” These were not novices. On average, the participants smoked pot about five times a week. Within twenty minutes, those who smoked the full-strength joint were moderately high, based on their own ratings and physical measures, like pulse rate. Those who smoked the placebo did not show the same physiological changes.

At this point, all thirty studied.

They were handed sheets of paper and given a minute and a half to try to commit to memory forty-eight words. The words appeared grouped by category—for example, “A type of vehicle—streetcar, bus, helicopter, train,” or “A musical instrument—cello, organ, trumpet, banjo.” The categories were part of the experimental manipulation. We all look for patterns when trying to memorize a long list of items, bunching together those that look or sound the same, or are somehow related. The scientists wanted to see whether smoking pot influenced these “higher-order” cues we use to retrieve information later on, so they provided the categories. When the ninety seconds were up, the papers were taken away.

Four hours later, when the effects of the drug had worn off, the participants returned to the lab and had another smoke. Some who’d been given a real joint the first time got a placebo this time around, and vice versa. Others smoked the same type both times. Twenty minutes later, without further study, they took a test.

Some got a free recall test, writing down as many of the words as they could remember in six minutes. Others took a “cued recall” test, in which they saw the list of categories (“A type of vehicle”) and filled in as many of the words in that category as they could. And sure enough—on the free recall—those who’d smoked a real joint on both occasions remembered 40 percent more than those who got a real one to study and a placebo for the test. The reverse was also true to a lesser extent: Those who initially studied on the placebo joint did
better after smoking another placebo, compared to a real joint. The participants’ memories functioned best when their brain was in the same state during study as during testing, high or not high.

Why? The cued-recall test (the one with the categories) helped provide an answer. The scores on this test were uniformly high, no matter what the students smoked or when. This finding suggests that the brain stores roughly the same
number
of words when moderately high as when not—the words are in there, either way. Yet it must organize them in a different way for later retrieval. That “retrieval key” comes back most clearly when the brain is in the same state, stoned or sober. The key becomes superfluous, however, when the categories are printed right there on the page. There’s no need for it, because an external one is handy. As the authors wrote, “The accessibility of retrieval cues which have been encoded in drug associated state—such as that produced by a moderate dose of marijuana—appears to depend, in part, on restoration of that state at
the time of desired recall.”

The joint-placebo study also gives us an idea how strong these internal, drug-induced memory cues are. Not so strong. Give someone a real hint—like a category name—and it easily trumps the internal cues. The same thing turned out to be true for alcohol and other drugs that these researchers and others eventually studied: Internal and external cues can be good reminders, but they pale next to strong hints.

The personality of the learning brain that emerges from all this work on external and internal cues is of a shifty-eyed dinner companion. It is tracking the main conversation (the homework assignment, the music notation, the hard facts) and occasionally becoming engaged in it. At the same time, it’s also periodically having a quick look around, taking in the room, sketching in sights and sounds and smells, as well as noting its internal reactions, its feelings and sensations. These features—the background music, a flickering candle, a
pang of hunger—help our companion recall points made during the conversation later on, especially when the topic is a new one. Still, a strong hint is better.

I think about this, again, in terms of the geometric proof of the Pythagorean theorem. Summoning up that late night scene in the math building three decades ago, I can begin to reconstruct the proof, but as I said it takes some futzing to get the triangles in place. However, if someone sketches out just part of the drawing, it all comes back immediately. The strong hint provided by a partial drawing trumps the weaker ones provided by reinstating my learning environment.

In a world that provided strong hints when needed, this system would be ideal. Just as it would be wonderful if, whenever we had to perform on some test, we could easily re-create the precise environment in which we studied, piping in the same music that was playing, dialing up the same afternoon light, the same mental state—all of the internal and external features that were present when the brain stored the material in the first place.

I’ll say this for those “Study Aids”: I could control where, when, and how much, and I believe that the vitamins allowed me to heap more information into my fragile mind at the times when I most needed to. Stimulants and other substances become a psychological crutch for so many for the same reason that researchers used them in studies—they’re a quick and reliable way to reproduce a particular mental state.

But there’s a better way. There’s a way to exploit the effects of internal and external cues without having to bet on any single environment or rely on a drug to power through.

• • •

Take a look at the table below and see if you detect any patterns, any system to group the numbers and letters in memory:

Give up? You should. There aren’t any good storage patterns, because the man who put it together invented it that way. He designed it to be as challenging as possible to remember, a random collection.

In the mid-1920s, Alexander Luria, a neuropsychologist at the University of Moscow, was studying memory when he met a newspaper reporter named Solomon Shereshevsky. Shereshevsky had been working at a city paper and behaving in ways that made his editor suspicious. Every morning, the staff gathered to go through a long list of the coming day’s activities—the events, people, and potential stories the editor wanted tracked. The reporters all took careful notes, except for Shereshevsky, who didn’t even bring a notebook. The boss, convinced the reporter was slacking, confronted him on it.

I don’t need to take notes, Shereshevsky replied, I just remember. He proceeded to detail that morning’s long list of assignments, without error. Not only that day’s but the previous day’s meeting, and the one before that. He just remembered things, he said. This performance struck the editor as so extraordinary that he
recommended that he go see Luria.

And so began a famous collaboration. For the next four decades, Luria tested and retested Shereshevsky—“S.,” as he called him in
print to protect his identity—eventually producing a panoramic exploration of one of the largest, most precise memories the world has known. S.’s feats of memory seemed beyond explaining. He could study an entire matrix of random numbers for fifteen minutes and recall the entire thing a week—a month, even a decade—later.

He could do the same for lists of words, for poems, for short reading selections, in his native Russian and in languages that were completely foreign to him, like Italian. Luria’s extensive interviews with S. about his memory, detailed in his book
The Mind of a Mnemonist
, revealed that S. had a condition called synesthesia, in which perceptions are mixed and unusually vivid. Sounds have shapes, colors; letters have taste, fragrance. “Even numbers remind me of images,” S. told Luria. “Take the number one. This is a proud, well-built man. Two is a high-spirited woman, three a gloomy person … as for the number 87, what I see is a fat woman and a
man twirling his mustache.” He attached an unusual number of cues to each thing he memorized, including internally generated images
and
details of the learning environment, like the sound of Luria’s voice.