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Monday, 23 July, 2001, 13:26 GMT 14:26 UK
Watching fights turns animals nasty
Nightingale, PA
Nightingales eavesdrop on each other's fights
By BBC News Online's Jo Kettlewell

Watching violent scenes could make animals more aggressive, a British zoologist says.

Rufus Johnstone of Cambridge University, UK, has developed a mathematical explanation of how some animals behave once they know the past record of a potential opponent.

His theory is a refinement of a classic explanation of animal behaviour known as the Hawk-Dove game.

He believes that animals watching rivals fight for resources gain information which makes them more likely to turn to violence to get their own way.

Reputation is everything

One might expect that animals eavesdropping on each other's fights would be less likely to fight, because they have a better idea of who is a tough customer and who is a pushover.

Any sensible underdog should back down before the fight breaks out.

But in a population of eavesdroppers, reputation is everything. If you know that watchful eyes surround your fight, it becomes all the more important to be seen to be a winner.

As a winner, you develop a "don't-mess-with-me" reputation, meaning other animals are less likely to pick a fight with you.

Hawks and doves

The quest for a tough reputation might actually encourage animals to be more aggressive than they would have been otherwise. This kind of behaviour has been observed in Siamese fighting fish and nightingales.

The Hawk-Dove game is a nice simple explanation of why it is that animals don't always go for an all out fight

Rufus Johnstone
The Hawk-Dove game predicts that aggressive or hawk-like behaviour is favoured over cautious or dove-like behaviour when "hawks" are rare.

But if hawks are common, they tend to do badly because they are more likely to run into an equally aggressive opponent and end up in a costly fight.

"The Hawk-Dove game is a nice, simple explanation of why it is that animals don't always go for an all-out fight," Dr Johnstone told BBC News Online.

Practical experiments

"But it's only a spring point, if you like, to move on and develop a more sophisticated theory," he added.

Winning not only grants you the immediate resource you are fighting for, but it also earns you the reputation as a winner

Rufus Johnstone
His interest was sparked by hearing about a series of practical experiments.

"There have been some nice results showing very clearly that if you let one individual see two others fighting then it will respond differently to the winner versus the loser of the fight.

"And that got me thinking. What would the implications of this kind of behaviour be for the evolution of aggression?" he said.


The answer, he predicted, is an increase in aggression.

"The paradoxical thing that emerges is that this strategy, that evolved as a way to avoid fights, ends up actually promoting more aggression.

"Basically, this is because if everyone is watching everyone else, trying to work out who is dangerous and who isn't, then it becomes all the more important to win.

"Winning not only grants you the immediate resource you are fighting for, but it also earns you the reputation as a winner.

"That reputation is valuable in its own right because it helps to deter future opponents," he said.

Human parallel?

Dr Johnstone says that his mathematical theory may also apply to humans.

The same kind of audience affect could occur in people

Rufus Johnstone
"Human behaviour is probably even more complex than that of other animals, but it seems to me the same logic ought to apply," he said.

"Humans, just like other animals, have an interest in what goes on, they have an interest in interactions between others. And they draw information from observing these interactions.

"So, the same kind of audience affect could occur in people.

"If reputation is important to you then the presence of an audience can urge you on to greater efforts."

Dr Johnstone's work is published in Proceedings of the National Academy of Sciences.

See also:

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