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WE all have something of the Greek god in us. Proteus to be precise, who
outwitted his enemies by constantly changing his shape. Humans may not go as far
as transmogrification but when it comes to confusing a rival, our talent for
erratic behaviour is second to none.

A rabbit pursued by a fox will bob and weave in a chaotic zigzag, rather than
make a beeline for cover. Other animals use different forms of random behaviour
to evade predators or catch their prey. But humans are the only ones who rely on
unpredictability as a weapon in competition against each other, whether it be in
a game of football or in international diplomacy.

Such behaviour has long been ignored, but researchers are now waking up to
the fact that not only can we behave in very random ways, but that such actions
are far from pointless. Unpredictable behaviour may have evolved as a way of
keeping our rivals in the dark. This could explain some of our strangest
behaviour, such as sudden mood swings, and it also adds a whole new dimension to
understanding the evolution of human intelligence. Our highly developed sense of
the erratic may be the spark that allows an ape adapted for savannah living to
paint the Sistine Chapel, design the space shuttle and invent advertising
slogans.

British biologist Michael Chance coined the phrase 鈥減rotean behaviour鈥� in
1959, while at the University of Birmingham. But the evolutionary explanation
for this phenomenon is less than a decade old. It began with the observation by
two British ethologists, Peter Driver and David Humphries, that many animals
develop cognitive capacities so that they can predict the actions of their
competitors or prey. Natural selection then favours mechanisms that make these
actions harder to predict, so their enemies evolve better predictive powers, and
an evolutionary arms race develops.

False signals

Two obvious ways of making your actions harder to predict are hiding your
real intentions and giving out false signals. Both of these, however, are still
vulnerable to the evolution of even better perceptual mechanisms on the part of
the enemy, and so are not evolutionarily stable strategies鈥攊n other words,
the arms race continues. In many conflicts the only way to stop this escalation
is to adopt what game theorists call a 鈥渕ixed strategy鈥�, which bases decisions
on probability. No amount of predictive talent will then prevail.

Submarine commanders in the Second World War hit on this idea and resorted to
throwing dice to choose random patrol routes and so evade destroyers. In nature,
interactions between enemies often work in a similar way. Sand eels, for
example, usually react to predators by bunching together and swimming in a
fast-moving school. But when threatened in a narrow pool, they behave very
differently鈥攖he school breaks up and each eel darts about in random
directions in an attempt to confuse the predator.

Driver and Humphries realised that protean behaviour should be common because
of the competitive edge it gives species. Once they began looking, they found
examples everywhere. There was the mobbing behaviour of gulls, which dive-bomb
intruders from all directions to try to protect nesting colonies. And the herds
of impala that burst into a whirlpool of activity, racing and plunging in every
direction when disturbed.

Proteanism could also make sense of some of the more bizarre interactions
between predators and prey. Many birds feign injury to lure the enemy away from
a nest full of fledglings, using random changes in speed and direction to
balance their aims of drawing attention away from their young and ensuring their
own survival. Another puzzle鈥攚hy moths, lizards and mice have mock
convulsions when attacked鈥攎akes sense as a way of throwing a predator off
its stride.

Competitive situations also bring out the Proteus in humans. But when
biologists looked at people, they noticed an important difference between us and
other animals鈥攐ur competitors tend to be other humans. Geoffrey Miller, a
psychologist at University College London, recently highlighted this and
suggested that this refinement in behaviour in our ancestors is key to our
unique cognitive style. Our talent for thinking randomly may even be a source of
the creative flare that sets humans apart from other animals.

Miller鈥檚 ideas build on the theory of Machiavellian intelligence, which
proposes that the main driving force in the evolution of human intelligence was
the need to predict and manipulate the behaviour of other humans. The special
cognitive capacities that evolved to deal with the social environment have been
dubbed social intelligence. This includes calculated deception and its
detection, but not protean behaviour. Miller argues that, in common with many
other animals, our monkey-like ancestors had a basic ability to act randomly
that they evolved to outwit predators. But during the transition from monkeys to
apes to early hominids, this protean capacity was boosted by positive feedback
from social intelligence, as outwitting our fellow humans became more important
than outwitting other animals. As a result, he claims, proteanism plays a
pivotal role in social intelligence.

Random rage

Miller gives the following example to illustrate why protean behaviour would
have evolved. Suppose our ancestors could have adopted one of two strategies for
setting their anger threshold鈥攖he point at which they lose their temper.
In the 鈥淥ld Faithful鈥� strategy, the anger threshold is fixed. Those who adopt
this strategy get angry only if an insult exceeds some predetermined level of
annoyance. In the 鈥淢ad Dog鈥� strategy, on the other hand, the anger threshold
varies randomly. Sometimes a big insult does not generate a response, but
sometimes a small insult does. Which strategy would have been more
effective?

If you are using Old Faithful, others quickly learn what they can get away
with, so they constantly push you to the limit. But against the Mad Dog strategy
any insult, however slight, might trigger retaliation. Furthermore, the person
using this strategy does not have to waste time and effort punishing every small
insult, because the uncertainty does most of the work. Flare up for no apparent
reason every now and then, and people will tend to tiptoe around you. So Mad Dog
is a much more effective way of outwitting your competitors.

鈥淭his might shed some light on the otherwise inexplicable nature of moods,鈥�
says Miller. When people explode over a minor insult that they would normally
have laughed off, we assume that some particular event has triggered their bad
mood. Miller, however, suggests that some moods may not be caused by any
specific stimulus. 鈥淭hey may simply be random alterations of our emotional
state,鈥� he says. 鈥淭he tendency to have such random mood changes could be a form
of protean behaviour that evolved to make us less predictable and so less easy
to exploit.鈥�

But are we really natural born randomisers? Until a few years ago, most
psychologists thought that humans were incapable of truly random behaviour.
Dozens of studies seemed to confirm the view that producing a random series of
responses is difficult, if not impossible for humans. But most of these
experiments involved placing people in very artificial, non-competitive
situations. Often, the researcher simply asked an isolated subject to write down
a series of numbers with an instruction such as 鈥渂e as random as possible鈥�. If
proteanism in humans evolved as a way of outwitting other humans, as Miller
argues, then people鈥檚 failure to generate random numbers in these situations is
not surprising. 鈥淧sychologists failed to tap into our natural randomising
abilities because they didn鈥檛 expose subjects to the social games where those
abilities evolved,鈥� says Miller.

So in 1992, two Israeli psychologists set out to test people in face-to-face
competition. David Budescu of the University of Haifa and Amnon Rapaport of the
Hebrew University of Jerusalem got people to play a game called matching
pennies. The rules are simple. Two players start with an equal number of coins.
Each turn, both players simultaneously place a coin on the table between them.
If the coins match (heads-heads or tails-tails), player A keeps both coins; if
not, player B keeps them.

Though the players have opposite objectives, they both benefit from being
able to predict what the other person will do next, and from making their own
moves hard to predict. Mathematically, the best strategy is to pick heads and
tails with equal probability, in a truly random series. Then over a long period
of play, your contestant cannot gain the advantage. And this is exactly what
Budescu and Rapaport found. The sequences of heads and tails generated by the
two players came very close to true mathematical randomness, even though the
players were given no instructions to that effect.

Another indication that randomness is an innate ability comes from the work
of Allen Neuringer of Reed College in Portland, Oregon. He has shown that humans
can learn to generate random sequences when given feedback. In one experiment,
Neuringer asked students to generate a random series of a hundred pairs of 1s
and 2s at a computer terminal. He then told the students how well they had done,
measuring their performance by whether, for example, the series included
approximately equal amounts of 1-1, 1-2, 2-1 and 2-2. In the first trial, the
series was always nonrandom, but after several trials, the students鈥�
performances improved to the point that their series could not be distinguished
from those generated by a computer.

A rat can learn to press a lever if you give it food as a reward, so is it
surprising that students learn to generate random numbers? Yes, says Miller. The
rat鈥檚 behaviour is an example of conditioning鈥攇ive it the right feedback
and it will learn a new trick. But conditioning works by gradually eliminating
random variation. 鈥淚t could never reinforce randomness itself,鈥� he says. This
leads him to conclude that there must be some innate randomising mechanism built
into the mind. 鈥淎 roulette wheel in the head鈥� is the metaphor used by John
Maynard Smith of the University of Sussex. 鈥淎ll sorts of processes can generate
effectively random series, so there is nothing bizarre about the idea that the
brain might be able to do so,鈥� he says.

Many animals seem to have this mental roulette wheel but, argues Miller, by
refining its abilities humans have developed a mechanism that is capable of more
than simply outwitting enemies. Our super-protean capacity is the basis for our
inventiveness and artistic creativity, he says. 鈥淧roteanism provides a key
element of creativity that other mental mechanisms lack鈥攖he capacity for
rapid, unpredictable generation of highly variable alternatives,鈥� says Miller.
Studies of human creativity often emphasis this element. Without it, for
example, there would be no brainstorming. And in many forms of art, from music
to comedy, coming up with a new twist on an old theme or confounding an
audience鈥檚 expectations is the key to success.

The prevailing view is that human creativity came about as a lucky accident,
through the increasing overlap of cognitive capacities designed for other
functions. Ecological intelligence evolved to meet the complex demands of
foraging for food in the savannah, technical intelligence developed with our
tool-making skills, and social intelligence with group living. In a recent book,
Steven Mithen, an archaeologist at the University of Reading, argued that in the
early hominid mind these intellectual specialities were walled off from each
other like the chapels of an early cathedral. He claims that the modern mind
evolved only with the collapse of these mental divisions and the development of
more general cognitive capacities.

Creative spur

The problem with this view, says Miller, is that it is at odds with one of
the main features of natural selection鈥攖hat it tends to lead to increased
specialisation rather than increased generalisation. Miller鈥檚 theory, however,
requires no appeal to increasingly general mechanisms. On the contrary, an
innate randomising mechanism could well be a very specialised way of generating
novel ideas. Miller speculates that it might work by amplifying the quantum
mechanical noise in synaptic activity. Alternatively, it could work in the same
way that computers generate random numbers: producing pseudo-randomness by
feeding the numbers it generates back into a program that is too complex to be
worked out by an outsider.

According to the Machiavellian intelligence hypothesis, creativity is a
spin-off from social intelligence alone. The idea is that our ancestors first
evolved to cope with savannah life, then learnt to exploit their environment
using tools, and finally perfected the art of social living. It was only then
that creativity really took off. But until now, nobody has come up with a
plausible explanation of how this might have happened. Miller鈥檚 theory could
have the answer by showing how proteanism evolved in the social setting, and
then making the link between randomness and creativity.

Evolutionary theorists have tended to see evolutionary adaptation as a
process that increases order and complexity. Natural selection was thought to
build improbable regularities from random disorder. Protean behaviour defies
this simple view鈥攊t is at once random and adaptive, chaotic and yet the
result of selection. No wonder it took biologists so long to see it.