The Power of Purposeful Practice

IN JUST OUR FOURTH SESSION together, Steve was already beginning to sound
discouraged. It was Thursday of the first week of an experiment that I had
expected to last for two or three months, but from what Steve was telling me, it
might not make much sense to go on. “There appears to be a limit for me
somewhere around eight or nine digits,” he told me, his words captured by the
tape recorder that ran throughout each of our sessions. “With nine digits
especially, it’s very difficult to get regardless of what pattern I use—you know,
my own kind of strategies. It really doesn’t matter what I use—it seems very
difficult to get.”
Steve, an undergraduate at Carnegie Mellon University, where I was teaching
at the time, had been hired to come in several times a week and work on a simple
task: memorizing strings of numbers. I would read him a series of digits at a rate
of about one per second—“Seven . . . four . . . zero . . . one . . . one . . . nine . . .”
and so on—and Steve would try to remember them all and repeat them back to
me once I was done. One goal was simply to see how much Steve could improve
with practice. Now, after four of the hour-long sessions, he could reliably recall
seven-digit strings—the length of a local phone number—and he usually got the
eight-digit strings right, but nine digits was hit or miss, and he had never
managed to remember a ten-digit string at all. And at this point, given his
frustrating experience over the first few sessions, he was pretty sure that he
wasn’t going to get any better.
What Steve didn’t know—but I did—was that pretty much all of
psychological science at the time indicated that he was right. Decades of
research had shown that there is a strict limit to the number of items that a
person can retain in short-term memory, which is the type of memory the brain
uses to hold on to small amounts of information for a brief period of time. If a
friend gives you his address, it is your short-term memory that holds on to it just
long enough to write it down. Or if you’re multiplying a couple of two-digit
numbers in your head, your short-term memory is where you keep track of all
the intermediate pieces: “Let’s see: 14 times 27 . . . First, 4 times 7 is 28, so keep
the 8 and carry the 2, then 4 times 2 is 8 . . .” and so on. And there’s a reason it’s
called “short-term.” You’re not going to remember that address or those
intermediate numbers five minutes later unless you spend the time repeating
them to yourself over and over again—and thus transfer them into your longterm
The problem with short-term memory—and the problem that Steve was
coming face-to-face with—is that the brain has strict limits on how many items
it can hold in short-term memory at once. For some it is six items, for others it
may be seven or eight, but the limit is generally about seven items—enough to
hold on to a local phone number but not a Social Security number. Long-term
memory doesn’t have the same limitations—in fact, no one has ever found the
upper limits of long-term memory—but it takes much longer to deploy. Given
enough time to work on it, you can memorize dozens or even hundreds of phone
numbers, but the test I was giving Steve was designed to present digits so fast
that he was forced to use only his short-term memory. I was reading the digits at
a rate of one per second—too fast for him to transfer the digits into his long-term
memory—so it was no surprise that he was running into a wall at numbers that
were about eight or nine digits long.
Still, I hoped he might be able to do a little better. The idea for the study had
come from an obscure paper I had discovered while searching through old
scientific studies, a paper published in a 1929 issue of the American Journal of
Psychology by Pauline Martin and Samuel Fernberger, two psychologists at the
University of Pennsylvania. Martin and Fernberger reported that two
undergraduate subjects had been able, with four months of practice, to increase
the number of digits they could remember when given the digits at a rate of
about one per second. One of the students had improved from an average of nine
digits to thirteen, while the other had gone from eleven to fifteen.
This result had been overlooked or forgotten by the broader psychological
research community, but it immediately captured my attention. Was this sort of
improvement really even possible? And, if so, how was it possible? Martin and
Fernberger had offered no details about how the students had improved their
digit memory, but that was exactly the sort of question that most intrigued me.
At the time, I was just out of graduate school, and my main area of interest was
the mental processes that take place when someone is learning something or
developing a skill. For my dissertation I had honed a psychological research tool
called “the think-aloud protocol” that was designed specifically to study such
mental processes. So in collaboration with Bill Chase, a well-known Carnegie
Mellon psychology professor, I set out to redo the old Martin and Fernberger
study, and this time I would be watching to see exactly how our subject
improved his digit memory—if indeed he did.
The subject we had recruited was Steve Faloon, who was about as typical a
Carnegie Mellon undergraduate as we could have hoped to find. He was a
psychology major who was interested in early childhood development. He had
just finished his junior year. His scores on achievement tests were similar to
those of other Carnegie Mellon students, while his grades were somewhat higher
than average. Tall and thin with thick, dark-blond hair, he was friendly, outgoing,
and enthusiastic. And he was a serious runner—a fact that did not seem
meaningful to us at the time but that would turn out to be crucial to our study.
On the first day that Steve showed up for the memory work, his performance
was dead-on average. He could usually remember seven digits and sometimes
eight but no more. It was the same sort of performance you would expect from
any random person picked off the street. On Tuesday, Wednesday, and Thursday
he was a little better—an average of just under nine digits—but still no better
than normal. Steve said he thought that the main difference from the first day
was that he knew what to expect from the memory test and thus was more
comfortable. It was at the end of that Thursday’s session that Steve explained to
me why he thought he was unlikely to get any better.
Then on Friday something happened that would change everything. Steve
found a way to break through. The training sessions went like this: I would start
with a random five-digit string, and if Steve got it right (which he always did), I
would go to six digits. If he got that right, we’d go to seven digits, and so on,
increasing the length of the string by one each time he got it right. If he got it
wrong, I would drop the length of the string by two and go again. In this way
Steve was constantly challenged, but not too much. He was given strings of
digits that were right at the boundary between what he could and couldn’t do.
And on that Friday, Steve moved the boundary. Up to that point he had
remembered a nine-digit string correctly only a handful of times, and he had
never remembered a ten-digit string correctly, so he had never even had a chance
to try strings of eleven digits or longer. But he began that fifth session on a roll.
He got the first three tries—five, six, and seven digits—right without a problem,
missed the fourth one, then got back on track: six digits, right; seven digits,
right; eight digits, right; nine digits, right. Then I read out a ten-digit number—
5718866610—and he nailed that one as well. He missed the next string with
eleven digits, but after he got another nine digits and another ten digits right, I
read him a second eleven-digit string—90756629867—and this time he repeated
the whole thing back to me without a hitch. It was two digits more than he had
ever gotten right before, and although an additional two digits may not seem
particularly impressive, it was actually a major accomplishment because the past
several days had established that Steve had a “natural” ceiling—the number of
digits he could comfortably hold in his short-term memory—of only eight or
nine. He had found a way to push through that ceiling.
That was the beginning of what was to be the most surprising two years of my
career. From this point on, Steve slowly but steadily improved his ability to
remember strings of digits. By the sixtieth session he was able to consistently
remember twenty digits—far more than Bill and I had imagined he ever could.
After a little more than one hundred sessions, he was up to forty, which was
more than anyone, even professional mnemonists, had ever achieved, and still he
kept going. He worked with me for more than two hundred training sessions, and
by the end he had reached eighty-two digits—eighty-two! If you think about that
for a moment, you’ll realize just how incredible this memory ability truly is.
Here are eighty-two random digits:
0 3 2 6 4 4 3 4 4 9 6 0 2 2 2 1 3 2 8 2 0 9 3 0 1 0 2 0 3 9 1 8 3 2 3 7 3 9 2
7 7 8 8 9 1 7 2 6 7 6 5 3 2 4 5 0 3 7 7 4 6 1 2 0 1 7 9 0 9 4 3 4 5 5 1 0 3 5
5 5 3 0
Imagine hearing all of those read out to you at one per second and being able
to remember them all. This is what Steve Faloon taught himself to do over the
two years of our experiment—all without even knowing it was possible, just by
continuing to work on it week after week.