Where
Computers Defeat Humans, and Where They Can’t
By
ANDREW McAFEE and ERIK BRYNJOLFSSON MARCH 16, 2016
ALPHAGO,
the artificial intelligence system built by the Google subsidiary DeepMind, has
just defeated the human champion, Lee Sedol, four games to one in the
tournament of the strategy game of Go.
Why
does this matter? After all, computers surpassed humans in chess in 1997, when
IBM’s Deep Blue beat Garry Kasparov. So why is AlphaGo’s victory significant?
Like
chess, Go is a hugely complex strategy game in which chance and luck play no
role. Two players take turns placing white or black stones on a 19by19 grid;
when stones are surrounded on all four sides by those of the other color they
are removed from the board, and the player with more surrounded territory and
captured stone at the game’s end wins.
Unlike
the case with chess, however, no human can explain how to play Go at the
highest levels. The top players, it turns out, can’t fully access their own
knowledge about how they’re able to perform so well.
This
self-ignorance is common to many human abilities, from driving a car in traffic
to recognizing a face. This strange state of affairs was beautifully summarized
by the philosopher and scientist Michael Polanyi, who said, “We know more
than we can tell.”
It’s
a phenomenon that has come to be known as “Polanyi’s Paradox.” Polanyi’s
Paradox hasn’t prevented us from using computers to accomplish complicated
tasks, like processing payrolls, optimizing flight schedules, routing telephone
calls and calculating taxes.
But
as anyone who’s written a traditional computer program can tell you, automating
these activities has required painstaking precision to explain exactly what the
computer is supposed to do. This approach to programming computers is severely
limited; it can’t be used in the many domains, like Go, where we know more than
we can tell, or other tasks like recognizing common objects in photos,
translating between human languages and diagnosing diseases — all tasks where
the rules-based approach to programming has failed badly over the years.
Deep
Blue achieved its superhuman performance almost by sheer computing power: It sifted
through millions of possible chess moves to determine the optimal move. The
problem is that there are many more possible Go games than there are atoms in
the universe, so even the fastest computers can’t simulate a meaningful
fraction of them. To make matters worse, it’s usually far from clear which
possible moves to even start exploring. What changed?
The
AlphaGo victories vividly illustrate the power of a new approach in which
instead of trying to program smart strategies into a computer, we instead build
systems that can learn winning strategies almost entirely on their own, by
seeing examples of successes and failures. Since these systems don’t rely on
human knowledge about the task at hand, they’re not limited by the fact that we
know more than we can tell.
AlphaGo
does use simulations and traditional search algorithms to help it decide on
some moves, but its real breakthrough is its ability to overcome Polanyi’s
Paradox. It did this by figuring out winning strategies for itself, both by
example and from experience. The examples came from huge libraries of Go
matches between top players amassed over the game’s 2,500year history. To
understand the strategies that led to victory in these games, the system made
use of an approach known as deep learning, which has demonstrated remarkable
abilities to tease out patterns and understand what’s important in large pools
of information.
Learning
in our brains is a process of forming and strengthening connections among
neurons. Deep learning systems take an analogous approach, so much so that they
used to be called “neural nets.” They set up billions of nodes and connections
in software, use “training sets” of examples to strengthen connections among
stimuli (a Go game in process) and responses (the next move), then expose the
system to a new stimulus and see what its response is.
AlphaGo
also played millions of games against itself, using another technique called
reinforcement learning to remember the moves and strategies that worked well.
Deep learning and reinforcement learning have both been around for a while, but
until recently it was not at all clear how powerful they were, and how far they
could be extended. In fact, it’s still not, but applications are improving at a
gallop, with no end in sight.
And
the applications are broad, including speech recognition, credit card fraud
detection, and radiology and pathology. Machines can now recognize faces and
drive cars, two of the examples that Polanyi himself noted as areas where we
know more than we can tell. We still have a long way to go, but the
implications are profound.
As
when James Watt introduced his steam engine 240 years ago, technology-fueled
changes will ripple throughout our economy in the years ahead, but there is no
guarantee that everyone will benefit equally. Understanding and addressing the
societal challenges brought on by rapid technological progress remain tasks
that no machine can do for us.
Andrew
McAfee is a principal research scientist at M.I.T., where Erik Brynjolfsson is
a professor of management. They are the cofounders of the M.I.T. Initiative on
the Digital Economy and the authors of “The Second Machine Age: Work, Progress,
and Prosperity in a Time of Brilliant Technologies.” Follow The New York Times
Opinion section on Facebook and Twitter, and sign up for the Opinion Today
newsletter. A version of this oped appears in print on March 16, 2016, on page
A23 of the New York edition with the headline: A Computer Wins by Learning Like
Humans.