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How do groups of animals make decisions?

* 9 January 2003 *

How do groups of animals make decisions?

Groups of animals often need to make communal decisions about what to do and when to do it. But how do they make such decisions?

Dr Larissa Conradt and Professor Tim Roper from the University of Sussex have developed a model that can be used to design experiments to establish how non-human animals make group decisions.

 Their model, reported in the journal Nature today (9 January), suggests that a social group in which all members contribute to a decision will be better equipped to survive than one where despotism reigns - even when the despot is the most experienced group member.

"Our model suggests that democratic decisions, being more beneficial than despotic decisions in most circumstances, should be widespread in animals," the authors say in their article. "Even when the despot is the most experienced group member, it only pays other members to accept its decision when group size is small and the difference in information is large."

It might be difficult to imagine how exactly animals make 'democratic' decisions at all without the ability to cast and count actual votes. However, studies show that voting behaviour can include body postures, movement and calls.

For example, a group of red deer will move when an average of 62 per cent of the group stands up. With bees, complex dances are used to make and convey decisions. Making 'democratic' decisions does not therefore require particularly advanced behaviour or mental ability.

* Notes for editors *

Larissa Conradt can be contacted on 01273 873502 or email

Tim Roper can be contacted on 01273 877373 or email

Press Office contacts: Peter Simmons or Alison Field, University of Sussex, Tel. 01273 678888, Fax 01273 877456, email or

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