Genghis Khan got around. At the
dawn of the 13thcentury, the Mongolian warrior conquered the largest empire the
world had ever known: an expanse stretching from the Sea of Japan in the east
to the Caspian Sea in the west, from Siberia in the north to India in the
south. To conquer this territory and then maintain his domination, the emperor
had to formulate complex plans. This created a problem: His soldiers were
illiterate peasants, scattered over thou-sands of miles. How could he spread
his complicated orders through the ranks quickly, simply, and without error?
His solution: Put the orders in a
song. All the Khan’s soldiers learned a small set of melodies, which they
practiced as they traversed the mountains and steppes. Then, when the time for
fighting arrived, commanders would set their orders to the tune of one of these
melodies. The soldiers’ task was simple: memorize a few new verses for an old
song, rather than a series of entirely unfamiliar, abstract instruc-tions. And
if any one of the soldiers forgot the lyrics, hundreds of others could sing him
the next line. Using this scheme, the soldiers crooned their battle
instructions, and large segments of Eurasia fell.
Others in the ancient world also
relied on deliberate memorization strategies. The Greeks of classical Athens,
for example, put a high value on public speaking, much of which was done from
memory. The Greeks therefore developed a number of memo-rization tricks to help
them in this endeavor.
Similar mnemonic tactics are used
in the modern world. Medical students, for example, have developed strategies
that help them memorize anatomy, drug names, and disease symptoms. Thus, they
learn the 12 pairs of cranial nerves (olfactory, optic, oculomotor, trochlear,
trigeminal, and so on) by taking the first letter of each word and forming a
sentence built from new words that start with the same letters. The resulting
sentence—“On Old Olympus’ Towering Tops A Friendly Viking Grew Vines and
Hops”—paints a vivid image that’s far easier to remember than the original
These examples remind us
that—with just a bit of work—we can get enormous amounts of information into
our memories, and then recall that information, in detail, for a very long
time. But there’s also a darker side to memory: Sometimes we remember things
that never happened at all. Indeed, far more often than we realize, our
memories blend together separate incidents, introduce rogue details, and
incorpo-rate others’ versions of events into our own recall.
How far off track can memory go?
In one study, researchers planted in participants a memory of getting lost in
the mall as a child, then being brought home safely by a friendly stranger.
Nothing of the sort had happened to anyone in the study, but they came to
vividly “remember” it anyhow. Other studies have planted false memories of
vicious animal attacks, and even—in one remarkable study—a false memory of a
hot-air balloon ride.
How should we put these pieces together? How does memory operate, so that we can easily remember countless episodes, thousands of facts, and the lyrics to hun-dreds of songs? Why does Genghis Kahn’s lyrical trick, or the medical students’ sentence-building strategy, help memory? More broadly, what can we do to learn more rapidly and hold on to the information longer? And why do our memories sometimes betray us, leading us to endorse large-scale fictions?