Brain Rules: 12 Principles for Surviving and Thriving at Work, Home, and School (21 page)

The evolutionary rationale for this observation is simple: Our East African crib did not unveil its sensory information one sense at a time during our development. It did not possess
only
visual stimuli, like a silent movie, and then suddenly acquire an audio track a few million years later, and then, later, smells and odors and textures. By the time we came out of the trees, our ancestors were encountering a multisensory world and were already champions at experiencing it.

Some interesting experiments support these ideas. Several years ago, scientists were able to peer in on the brain using fMRI technology. They played a trick on their subjects: They showed a video of someone speaking but completely turned off the sound. When the researchers examined what the brain was doing, they found that the area responsible for processing the sound, the auditory cortex, was stimulated as if the person actually were hearing sound. If the person was presented with a person simply “making faces,” the auditory cortex was silent. It had to be a visual input
related
to sound. Clearly, visual inputs influence auditory inputs, even with the sound turned off.

In another experiment at about the same time, researchers showed short flashes of light near the subjects’ hands, which were rigged with a tactile stimulator. Sometimes researchers would turn on the stimulator while the flash of light was occurring, sometimes not. No matter how many times they did this, the visual portion of the brain always lighted up the strongest when the tactile response was paired with it. They could literally get a boost in the visual system by introducing touch. This effect is called multimodal reinforcement.

Multiple senses affect our ability to detect stimuli, too. Most people, for example, have a very hard time seeing a flickering light if the intensity of the light is gradually decreased. Researchers decided to test that threshold by precisely coordinating a short burst of sound with the light flickering off. The presence of sound actually changed the threshold. The subjects found that they could see the light way beyond their normal threshold if sound was part of the experience.

These data show off the brain’s powerful integrative instincts. Knowing that the brain cut its developmental teeth in an overwhelmingly multisensory environment, you might hypothesize that its learning abilities are increasingly optimized the more multisensory the environment becomes. You might further hypothesize that the opposite is true: Learning is less effective in a unisensory environment. That is exactly what you find, and it leads to direct implications for education and business.

the learning link

Cognitive psychologist Richard Mayer probably has done more than anybody else to explore the link between multimedia exposure and learning. He sports a 10-megawatt smile, and his head looks exactly like an egg (albeit a very clever egg). His experiments are just as smooth: Divide the room into three groups. One group gets information delivered via one sense (say, hearing), another the same information from another sense (say, sight), and the third group the same information delivered as a combination of the first two senses.

The groups in the multisensory environments always do better than the groups in the unisensory environments. They have more accurate recall. Their recall has better resolution and lasts longer, evident even 20
years
later. Problem-solving improves. In one study, the group given multisensory presentations generated more than 50 percent more creative solutions on a problem-solving test than students who saw unisensory presentations. In another study, the improvement was more than 75 percent!

The benefits of multisensory inputs are physical as well. Our muscles react more quickly, our threshold for detecting stimuli improves, and our eyes react to visual stimuli more quickly. It’s not just combinations of sight and sound. When touch is combined with visual information, recognition learning leaps forward by almost 30 percent, compared with touch alone. These improvements are greater than what you’d predict by simply adding up the unisensory data. This is sometimes called supra-additive integration. In other words, the positive contributions of multisensory presentations are greater than the sum of their parts. Simply put, multisensory presentations are the way to go.

Many explanations have been put forth to explain these consistent findings, and most involve working memory. You might recall from Chapter 5 that working memory, formerly called short-term memory, is a complex work space that allows the learner to hold information for a short period of time. You might also recall its importance to the classroom and to business. What goes on in the volatile world of working memory deeply affects whether something that is taught will also be learned.

All explanations about multisensory learning also deal with a counter-intuitive property lurking at its mechanistic core: Extra information given at the moment of learning makes learning better. It’s like saying that if you carry two heavy backpacks on a hike instead of one, you will accomplish your journey more quickly. This is the “elaborative” processing that we saw in the chapter on short-term memory. Stated formally: It is the extra cognitive processing of information that helps the learner to integrate the new material with prior information. Multisensory experiences are, of course, more elaborate. Is that why they work? Richard Mayer thinks so. And so do other scientists, looking mostly at recognition and recall.

One more example of synesthesia supports this, too. Remember Solomon Shereshevskii’s amazing mental abilities? He could hear a list of 70 words once, repeat the list back without error (forward or backward), and then reproduce the same list, again without error, 15 years later. Shereshevskii had multiple categories of (dis)ability. He felt that some colors were warm or cool, which is common. But he also thought the number 1 was a proud, well-built man, and that the number 6 was a man with a swollen foot, which was not common. Some of his imaging was nearly hallucinatory. He related: “One time I went to buy some ice cream … I walked over to the vendor and asked her what kind of ice cream she had. ‘Fruit ice cream,’ she said. But she answered in such a tone that a whole pile of coals, of black cinders, came bursting out of her mouth, and I couldn’t bring myself to buy any ice cream after she had answered that way.”

Shereshevskii clearly is in his own mental universe, but he illustrates a more general principle. Synesthetes almost universally respond to the question “What good does this extra information do?” with an immediate and hearty “It helps you remember.” Given such unanimity, researchers have wondered for years if there is a relationship between synesthesia and advanced mental ability.

There is. Synesthetes usually display unusually advanced memory ability—photographic memory, in some cases. Most synesthetes report the odd experiences as highly pleasurable, which may, by virtue of dopamine, aid in memory formation.

rules for the rest of us

Over the decades, Mayer has isolated a number of rules for multimedia presentation, linking what we know about working memory with his own empirical findings on how multimedia exposure affects human learning. Here are five of them in summary form:

1) Multimedia principle:
Students learn better from words and pictures than from words alone.

2) Temporal contiguity principle:
Students learn better when corresponding words and pictures are presented simultaneously rather than successively.

3) Spatial contiguity principle:
Students learn better when corresponding words and pictures are presented near to each other rather than far from each on the page or screen.

4) Coherence principle:
Students learn better when extraneous material is excluded rather than included.

5) Modality principle:
Students learn better from animation and narration than from animation and on-screen text.

Though wonderfully empirical, these principles are relevant only to combinations of two senses: hearing and vision. We have three other senses also capable of contributing to the educational environment. Beginning with the story of a talented combat veteran, let’s explore what happens if we add just one more: smell.

nosing it out

I once heard a story about a man who washed out of medical school because of his nose. To understand his story, you have to know something about the smell of surgery. And you have to have killed somebody. Surgery can be a smelly experience. When you cut somebody’s body, you invariably cut their blood vessels. To keep the blood from interfering with the operation, surgeons use a cauterizing tool, hot as a soldering iron. It’s applied directly to the wound, burning it shut, filling the room with the acrid smell of smoldering flesh. Combat can smell the same way. And the medical student in question was a Vietnam vet with heavy combat experience. He didn’t seem to suffer any aversive effects when he came home. He had no post-traumatic stress disorder, and he became a high-functioning undergraduate, eventually accepted into medical school. But then the former soldier started his first surgery rotation. Entering the surgical suite, he promptly smelled the burning flesh from the cauterizer. The smell brought back to mind the immediate memory of an enemy combatant he had shot in the face, point blank, an experience he had suppressed for years. The memory literally doubled him over. He ran out of the room crying, the dying enemy’s strange gurgling sounds ringing in his ears, the noises of the evacuation helicopters in the distance. All that day, he relived the experience; later that night, he began to recall in succession other equally terrible events. He resigned from the program the next week.

This story illustrates something scientists have known for years: Smell can evoke memory. It’s called the Proust effect. Marcel Proust, the French author of the profoundly moving book
Remembrance of Things Past
, talked freely 100 years ago about smells and their ability to elicit long-lost memories. Typical experiments have investigated the unusual ability of a smell to enhance retrieval. Two groups of people might be assigned to see a movie together, for example, and then told to report to the lab for a memory test. The control group goes into an unmanipulated room and simply takes the test. The experimental group takes the test in a room flooded with the smell of popcorn. The results are then compared, scoring for number of events recalled, accuracy of events recalled, specific characteristics, and so on. The results of the test can be astonishing. Some researchers report that smell-exposed experimental groups can accurately retrieve twice as many memories as the controls. Others report a 20 percent improvement, still others only a 10 percent.

One way to react to these data is to say, “Wow.” Another is to ask, “Why the disparity in results?” One big reason is that the results depend on the type of memory being assessed and the methodology employed to obtain them. For example, researchers have found that certain types of memory are exquisitely sensitive to smells and other types nearly impenetrable. Odors appear to do their finest work when subjects are asked to retrieve the emotional details of a memory, as our medical student experienced, or to retrieve autobiographical memories. You get the best results if the smells are congruent. A movie test in which the smell of gasoline is pumped into the experimental room does not yield the same positive memory-retrieval results as the smell of popcorn does.

Odors are not so good at retrieving declarative memory. You can get smell to boost declarative scores, but only if the test subjects are emotionally aroused—usually, that means stressed—before the experiment begins. (For some reason, showing a film of young Australian aboriginal males being circumcised is a favorite way to do this). Recent tests, however, show that smell can improve declarative memory recall during sleep, a subject we will take up in a moment. Is there a reason why the Proust effect exists—why smell evokes memory? There might be, but to understand it, we have to know a little bit about how smell is processed in the brain.

Right between the eyes lies a patch of neurons about the size of a large postage stamp. This patch is called the olfactory region. The outer surface of this region, the one closest to the air in the nose, is the olfactory epithelium. When we sniff, odor molecules enter the nose chamber and collide with nerves there. This in itself is amazing, given that the chamber is always covered by a thick layer of snot. Somehow these persistent biochemicals penetrate the mucus and brush against little quill-like protein receptors that stud the nerves in the olfactory epithelium. The receptors can recognize a large number of smell-evoking molecules. When that happens, the neurons begin to fire excitedly, and you are well on your way to smelling something. The rest of the journey occurs in the brain. The now occupied nerves of the olfactory epithelium chat like teenagers on a cell phone to a group of nerves lying directly above them, in the olfactory bulb. These nerves help sort out the signals sent to it by the epithelium.

Here comes the interesting part of the story. Every other sensory system, at this point, must send a signal to the thalamus and ask permission to connect to the rest of the brain—including the higher levels where perception occurs. Not the nerves carrying information about smell. Like an important head of state in a motorcade, smell signals bypass the thalamus and go right to their brainy destinations, no meddling middle-man required.

One of those destinations is the amygdala, and it is at this point that the Proust effect begins to make some sense. As you recall, the amygdala supervises not only the formation of emotional experiences but also the
memory
of emotional experiences. Because smell directly stimulates the amygdala, smell directly stimulates emotions. Smell signals also head through the piriform cortex to the orbitofrontal cortex, a part of your brain just above and behind your eyes and deeply involved in decision making. So smell plays a role in decision making. It is almost as if the odor is saying, “My signal is so important, I am going to give you a memorable emotion. What are you going to do about it?”