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Robots at Work
Courtesy of New Scientist Magazine
It's amazing what you can do with a soldering iron, a few wires and a
dynamite theory about neurons.
PICTURE this. A simple machine that searches its environment, navigates round obstacles
and is attracted by light. Such a beast sounds like the latest in artificial life: a robot
that behaves just like an animal.
Alive it may be. But its not new and contains no silicon. It is controlled by a handful of
valves and was made by a man ahead of his time, William Grey Walter.
Born in 1910 in Kansas City, Missouri, Walter was educated in England and chose to work in
neurophysiology at a time when the field was starting to buzz. In Russia, Ivan Pavlov was
creating a sensation with his experiments on conditioned reflexes. The results are well
known: once a dog has been trained to associate the sound of a bell with food, it will
salivate when the bell rings, even when no food is around. What impressed the young
Walter, who met Pavlov, was the deftness with which the Russian isolated his experiment
from the myriad activities of the brain, letting him study just two stimuli--the food and
In 1928, neurophysiology received another boost when a German, Hans Berger, invented the
electroencephalograph and discovered brain waves. As a young man, Walter visited Berger's
lab and found his device surprisingly crude. He was always an inveterate tinkerer and
decided to refine the machine. Where Berger saw rhythmic fluctuations at about 10
hertz--alpha waves--Walter's more sensitive EEG identified other rhythms. He named the
theta rhythms at about 5 hertz and delta rhythms down as low as 0·5 hertz.
This work established his reputation and in 1939 he moved to the Burden Neurological
Institute in Bristol, where he worked until just before his death in 1977.
Walter's interest in Alife grew out of his work in neurophysiology. To unravel the
complexities of the brain, he proposed building electronic models. But he also recognized
the obstacle posed by the sheer number of neurons. "If the secret of the brain's
elaborate performance lies there, in the number of its units, that would be indeed the
only road, and that road would be closed," he wrote in his book The Living Brain. The
only hope was if the number of cells was not so important as "the richness of their
In 1948, Walter built his first robot, a three-wheeled "tortoise", covered by a
plastic shell and controlled by just two neurons--a pair of interlinked amplifiers. These
amplifiers connected two sensors to two motors. The first sensor, a light-sensitive cell,
was fixed to the spindle that steered the single drive wheel, and faced in the same
direction as the wheel. One motor steered the machine by turning the spindle, while the
other drove the wheel round. The second sensor was a simple contact switch that closed
whenever a tortoise's shell bumped into something. This "contact reflex"
temporarily tipped one of the amplifiers into oscillation.
From these simple connections grew a wealth of complex behaviors. Normally, the photocell
"scanned" round and round while the drive wheel revolved at half speed, sending
the tortoise in a series of graceful curves in search of dim lights. Walter called the
creature Machina speculatrix because "it explores its environment actively,
persistently, systematically as most animals do".
When the machine detected a light, it stopped scanning and raced towards it. But if the
light became too bright, a dazzled M. speculatrix began to scan again, turning away from
the light. If it hit an object, the contact reflex would switch the machine between its
normal and dazzled states, so that it repeatedly backed and turned until it had negotiated
All this was expected. But more interesting things happened when Walter attached lamps to
the tortoise's nose. The lamp was normally on, but went off whenever it spotted another
light source. When placed in front of a mirror the robot began "flickering,
twittering, and jigging like a clumsy Narcissus", wrote Walter. This behavior, he
argued, if seen in an animal, "might be accepted as evidence of some degree of
Walter built M. speculatrix for a very specific purpose, says Owen Holland of the
University of the West of England, Bristol, who has restored Walter's robots. "He
wanted to prove that rich connections between a small number of brain cells produces very
rich behavior," he says.
The idea of using just a few components to generate complex behavior has a distinctly
modern feel to it. In the late 1980s, Rodney Brooks of the Massachusetts Institute of
Technology used the idea to lay the foundations of a field that has since become known as
behavior-based robotics. Earlier "intelligent" robots carried large control
programs that decided their every move. Typically, these robots managed only very specific
tasks and were stumped if they put a foot wrong.
Brooks threw out this method of "top-down" control in favor of a
"bottom-up" approach in which he delegated control to very simple elements. Each
leg of his walking robot, Genghis, controlled its own actions using sensors and motors
linked by a small amount of processing power. Simply by timing the activities of these
processors, the robot could walk and avoid objects or clamber over them.
In formulating his approach, Brooks drew on Walter's work. As a child, Brooks had read
Walter's book and built his own versions of the machines described in it. The robots
designed by both men are busy, "inquisitive" machines that adapt to the world
The animal-like behavior of M. speculatrix noted by Walter is another trait singled out by
adherents of behavior-based robotics. The surprise emergence of unpredictable behavior,
such a hallmark of the natural world, is key to their claims that they are progressing
towards truly lifelike artificial organisms.
Walter's next robot behaved even more like an animal. Machina docilis could be trained in
much the same way as Pavlov had trained his dogs. It was actually M. speculatrix wearing
on its back what Walter called the Conditioned Reflex Analogue (CORA). This created a
connection between the robot's light reflex or its contact reflex and a third stimuli--a
whistle. He trained the machine by blowing the whistle and then, for example, kicking it
to trigger the contact reflex. "After five or six beatings, whenever the whistle was
blown [M. docilis] turned and backed from an 'imagined' obstacle," Walter wrote.
At the heart of CORA was a capacitor connected to both inputs--sound and contact. If a
kick followed straight after a whistle, the capacitor charged up until it reached a
threshold. At this point it discharged and opened an electronic gate that allowed the
whistle to stimulate the same response as kicking the machine. If this conditioning wasn't
reinforced, it wore off and CORA shut the gate.
Walter described how his robots helped him to study different aspects of behavior and the
brain. Ironically, while many of his theories have long since been laid to rest, the
significance of his robots and the ideas that underpin them are only now being realized.
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